Targetting Pathways: Manipulating Regulatory Genes

Role of Transcription Factors in the Activation of Stress Responsive Genes

A striking strategy for manipulation and gene regulation is the small group of transcription factors that have been identified to bind to promoter regulatory elements in genes that are regulated by abiotic stresses (Shinozaki and Yamaguchi-Shinozaki 1997; Winicov and Bastola 1997). The transcription factors activate cascades of genes that act together in enhancing tolerance towards multiple stresses.

Dozens of transcription factors are involved in the plant response to drought stress (Vincour and Altman 2005; Bartels and Sunkar 2005). Most of these falls into several large transcription factor families, such as AP2/ERF, bZIP, NAC, MYB, MYC, Cys2His2 zinc-finger and WRKY. Individual members of the same family often respond differently to various stress stimuli. On the other hand, some stress responsive genes may share the same transcription factors, as indicated by the significant overlap of the gene expression profiles that are induced in response to different stresses (Seki et al, 2001; Chen and Murata 2002). Transcriptional activation of stress-induced genes has been possible in transgenic plants over expressing one or more transcription factors that recognize promoter regulatory elements of these genes. Two families, bZIP and MYB, are involved in ABA signaling and its gene activation. Many ABA inducible genes share the (C/T) ACGTGGC consensus, cis-acting ABA-responsive element (ABRE) in their promoter regions (Guiltinan et al., 1990; Mundy et al., 1990). Introduction of transcription factors in the ABA signaling pathway can also be a mechanism of genetic improvement of plant stress tolerance. Constitutive expression of ABF3 or ABF4 demonstrated enhanced drought tolerance in Arabidopsis, with altered expression of ABA/stress-responsive genes, e.g. rd29B, rabl8, ABI1 and ABI2 (Kagaya et al., 2002). Several ABA-associated phenotypes, such as ABA hypersensitivity and sugar hypersensitivity, were obseived in such plants. Moreover, salt hypersensitivity was observed in ABF3- and ABF4-over expressing plants at the germination and young seedling stages indicating the possible participation of ABF3 and ABF4 in response tosalinityat these particular developmental stages. Improved osmotic stress tolerance in35S:At-MYC2/AtMYB2 transgenic plants as judged by an electrolyte-leakage test was reported by (Abebe et al., 2003). Transgenic Arabidopsis plants constitutively over-expressing a cold inducible transcription factor (CBF1; CRT/DRE binding protein) showed tolerance to freezing without any negative effect on the development and growth characteristics (Jaglo- Ottosen et al, 1998). Over expression of Arabidopsis CBF1 (CRT/DRE binding protein) has been shown to activate or homologous genes at non-acclimating temperatures (Jaglo et al., 2001). The CBF1 cDNA when introduced into tomato (Lycopersicon esculentum) under the control of a CaMV35S promoter improved tolerance to chilling, drought and salt str ess but exhibited dwarf phenotype and reduction in fruit set and seed number (Hsieh et al., 2002).

Another transcriptional regulator, Alfinl, when over expressed in transgenic alfalfa (Medicago sativa L.) plants regulated endogenous MsPRP2 (NaCl-inducible gene) mRNA levels, resulting in salinity tolerance, comparable, to a few available salt tolerant plants (Winicov and Bastola 1999). Lee et al. (1995) produced thermo- tolerant Arabidopsis plants by de-repressing the activity of ATHSF1, a heat shock transcription factor leading to the constitutive expression of heat shock proteins at normal temperature. Several stress induced cor genes such as rd29A, corl5A, kinl and согб.б are triggered in response to cold treatment, ABA and water deficit stress (ThomashoT998).

The promoters of stress responsive genes have typical cri-regulatory elements like DRE/CRT, ABRE, MYCRS/MYBRS and are regulated by various upstream transcriptional factors (Figure 4). These transcription factors fall in the category of early genes and are induced within minutes of stress. The transcriptional activation of some of the genes including RD29A has been well worked out. The promoter of this gene family contains both ABRE as well as DRE/ CRT elements (Stockinger and Gilmour, 1997). Transcription factors, which can bind to these elements were isolated and were found to belong to AP2/EREBP family and were designated as CBF1/ DREB1B, CBF2/DREB1C, and CBF3/DREB1A (Medina et al, 1999). These transcription factors (CBF1, 2 and 3) are cold responsive and in turn bind CRT/DRE elements and activate the transcription of various stress responsive genes. A novel transcription factor responsive to cold as well as ABA was isolated from soybean and termed as SCOF-1 (soybean zinc finger protein). This transcription factor, however, was not responsive to drought or salinity stress. SCOF1 was a zinc finger nuclear localized protein but failed to bind directly to either CRT/DRE or ABRE elements. Yeast 2-hybrid study revealed that SCOF-1 interacted strongly with SGBF-1 (Soybean G-box bind-ing bZip transcription factor) and hi vitro DNA binding activity of SGBF-1 to ABRE elements was greatly unproved by the presence of SCOF-1. This study supported that protein-protein interaction is essential for the activation of ABRE-mediated cold responsive genes. Transcription factors like DREB2A and DREB2B gets activated in response to dehydration and confer tolerance by induction of genes involved in maintaining the osmotic equilibrium of the cell (Liu et al, 1998). Several basic leucine zipper (bZip) transcription factors (namely ABF/AREB) have been isolated which can specifically bind to ABRE element and activate the expression of stress genes (Choi et al, 2000). These AREB genes (AREB1 and AREB2) are ABA responsive and need ABA for their frill activation. These transcription factors exhibited reduced activity in the ABA-deficient mutant aba2 as well as in ABA insensitive mutant aba 1-1. Some of the stress responsive genes for example RD22 lack the typical CRT/DRE elements in their promoter indicating their regulation by other mechanisms. Transcription factor RD22BP1 (a MYC transcription factor) and AtMYB2 (a MYB transcription factor) could bind MYCRS (MYC recognition sequence) and MYBRS (MYB recognition sequence) elements, respectively, and could cooperatively activate the expression of RD22 gene (Abe et al, 1997). As cold, salinity and drought stress ultimately impair the osmotic equilibrium of the cell it is likely that these transcription factors as well as the major stress genes may cross talk with each other for their maximal response and help in reinstating the normal physiology of the plant. ABA is an important phytohormone and plays a critical role in response to various stress signals. The application of ABA to plant mimics the effect of a stress condition. As many abiotic stresses ultimately results in desiccation of the cell and osmotic imbalance, there is an overlap in the expression pattern of stress genes after cold, drought, high salt or ABA application. This suggests that various stress signals and ABA share common elements in their signaling pathways and these common elements cross talk with each other, to maintain cellular homeostasis (Finkelstein et ah, 2002). Functions of ABA include: 1) ABA causes seed dormancy and delays its germination. 2) ABA promotes stomatal closure.

ABA levels are induced in response to various stress signals. ABA actually helps the seeds to surpass the stress conditions and germinate only when the conditions are conducive for seed germination and growth. ABA also pre-vents the precocious germination of premature embryos. Stomatal closure under drought conditions prevents the intracellular water loss and thus ABA is aptly called as a stress hormone. The main function of ABA seems to be the regulation of plant water balance and osmotic stress tolerance. Several ABA deWcient mutants namely abal, aba2 and aba3 have been reported for Arabidopsis (Koomneef et ah, 1998).

There have been numerous efforts in enhancing tolerance towards multiple stresses such as cold, drought and salt stress in crops other than the model plants like Ar abidopsis, tobacco and alfalfa. An increased tolerance to freezing and drought in Arabidopsis was achieved by over expressing CBF4, a close CBF/ DREB1 homolog whose expression is rapidly induced during drought stress and by ABA treatment, but not by cold (Haake et ah, 2002). Similarly, a cis-acting element, dehydration responsive element (DRE) identified in A. thaliana, is also involved in ABA-independent gene expression under drought, low temperature and high salt stress conditions in many dehydration responsive genes like rd29A that are responsible for dehydration and cold-induced gene expression (Yamaguchi-Shinozaki and Shinozaki 1993; Iwasaki et ah, 1997; Nordin et ah, 1991). Several cDNAs encoding the DRE binding proteins, DREB1A and DREB2A have been isolated from A. thaliana and shown to specifically bind and activate the transcription of genes containing DRE sequences(Liu et ah, 1998). DREBl/CBFs are thought to function in cold-responsive gene expression, whereas DREB2s are involved in drought-responsive gene expression. The transcriptional activation of stress-induced genes has been possible in transgenic plants over-expressing one or more transcription factors that recognize regulatory elements of these genes. In Arabidopsis, the transcription factor DREB1A specifically interacts with the DRE and induces expression of stress tolerance genes (Shinozaki and Yamaguchi- Shinozaki 1997). DREB1A cDNA under the control of CaMY 35S promoter in transgenic plants elicits strong constitutive expression of the stress inducible genes and brings about increased tolerance to freezing, salt and drought stresses (Liu et ah, 1998). Strong tolerance to freezing stress was observed in transgenic Arabidopsis plants that over express CBF1 (DREB1B) cDNA under the control of the CaMV 35S promoter (Jaglo-Ottosen et ah, 1998). Subsequently, the over expression of DREB1A has been shown to improve the drought and low- temperature stress tolerance in tobacco, wheat and groundnut (Kasuga et al.,

Gene

Gene Action

Species

Phenotype

Reference

ABF3

Transcription factor

Rice

Drought resistance

Oh et al., 2005

ABP9

ABRE binding protein9

Arabidopsis

Regulation of plant photosynthesis under stress

Zhang et al., 2008

ABP9

ABRE binding protein9

Arabidopsis

drought and salt stress tolerance

Zhang et al., 2011

AISAP

Transcription factor

Tobacco

Drought, salinity and freezing tolerance

Ben Saad et al., 2010

ALDH3I1 & ALDH7B4

Aldehyde dehydrogenase

Arabidopsis

Salt and dehydration stress tolerance

Kotchoni et al., 2006

ZmALDH22A1

Aldehyde dehydrogenase

Tobacco

Salt and dehydration tolerance

Huang et al., 2008

Alx8

High APX2 and ABA

Arabidopsis

Drought tolerance

Rossel et al., 2006

AnnAtl

Annexin synthesis

Arabidopsis

Drought tolerance

Konopka-Postupolska et al., 2009

AnnBjl

Annexin synthesis

Cotton

Salt and osmotic resistance

Divya et al., 2010

AP37

Transcription factor

Rice

Drought tolerance in yield

Oh et al., 2009

S|AREB1

ABA-responsive element binding protein

Tomato

Salinity and drought tolerance

Orellana et al., 2010

ASR1

Undetermined

Tobacco

Decreased water loss; salt tolerance

Kalifa etal., 2004

HvCBF4

Induced expression of COR genes

Rice

Drought resistance

Lourengo et al., 2011

AtCML9

Transcription factor

Arabidopsis

Drought and salt tolerance

Magnan et al., 2008

AtCPK6

Calcium-dependent protein kinase

Arabidopsis

Salt and drought tolerance

Xu etal., 2010

OSCPK21

Calcium-dependent protein kinase

Rice

Salt tolerance

Asano et al., 2011

AtGSKI

Homologue of GSK3/ shaggy like protein kinase

Arabidopsis

Salt tolerance in plant and root growth

Piao et al.,2001

Gene

Gene Action

Species

Phenotype

Reference

ATHB6

Transcription factor

Tomato

Drought resistance

Mishra et al., 2012

AtMYB102

Chimeric repressors

Arabidopsis, rice

Salt tolerance

Mito et al., 2011

GhMT3a

Metallothionein synthesis and ROS scavenging

Tobacco

Drought, salt, cold tolerance

Xue et al., 2009

AtNOAl

Nitric Oxide synthesis

Arabidopsis

Salt tolerance

Zhao et al., 2007

AtNOAl

Nitric Oxide synthesis

Arabidopsis

Salt tolerance

Qiao et al., 2009

OsPR4

Transcription factor

rice

Drought resistance

Wang et al., 2011

AtRabG3e

Intracellular vesicle trafficking

Arabidopsis

Salt and osmotic stress tolerance

Mazel eta!., 2004

GhDi19-1

GhDi19-2

Cys2/His2-Type Zinc-Finger Proteins

Arabidopsis

Salt and ABA sensitivity

Li et al., 2010

AtSZFI& AtSZF2

CCCH-type zinc finger proteins, involved in salt stress responses

Arabidopsis

Salt tolerance

Sun et al., 2007

StZFPI

TFIIIA-type zinc finger protein

Tobacco

Salt tolerance

Tian et al., 2010

At-SR05

Antioxidative action

Arabidopsis

Salt tolerance

Rabajani et al., 2009

BnPtdlns-PLC2

Phosphatidylinositol-specific phospholipase C

Canola

Drought resistance, early flowering

Georges et al., 2009

CAbZIPI

Plant development (dwarf phenotype)

Arabidopsis

Drought and salt tolerance

Lee et al., 2006

AtbZIP17

Transcription factor

Arabidopsis

Salt tolerance

lu et al., 2008

BAX

BCL2-associated x protein as the pro-PCD factor

Tobacco

Drought, salt and heat tolerance

Isbat et al., 2009

Gene

Gene Action

Species

Phenotype

Reference

bZIP23

Transcription factor

Rice

ABA sensitivity, drought and salt tolerance Xiang et al., 2008

ZIP72

Transcription factor

Rice

ABA sensitivity and drought resistance

Lu et al., 2009

ThbZIPI

Transcription factor

Tobacco

Salt tolerance and antioxidant activity

Wang et al., 2010

CAP2

Transcription factor

Tobacco

Drought and salt tolerance

Shukla et al., 2006

CBF3

Transcription factor

Rice

Drought and salt resistance

Oh et al., 2005

CBF4

Transcription factor

Arabidopsis

Drought and freezing tolerance (via activation of C-repeat/dehydration responsive element)

Haake et al., 2002

CBL1

Ca sensing protein

Arabidopsis

Salt and drought tolerance & cold sensitivity

Cheong et al., 2003

CBL1

Ca sensing protein

Arabidopsis

Salt and drought resistance - reduced transpiration

Albrecht et al., 2003

CBL1

Ca sensing protein

Arabidopsis

Salt tolerance

Wang et al., 2007

CBP20

cap binding complex

Arabidopsis

Loss of function (recessive) induces drought resistance

Papp et al., 2004

CcHyPRP

A hybrid-proline-rich protein encoding gene

Arabidopsis

Heat, salt and osmotic resistance

Priyanka et al., 2010

CpMYBIO

Glucose sensitive and ABA hypersensitive

Arabidopsis

Desiccation and salinity tolerance

Villalobos et al., 2004

DREB

Transcription factor

Arabidopsis

Increased tolerance to cold, drought and salinity

Kasuga et al., 1999

DREB

Transcription factor

Arabidopsis

Saliity tolerance

Xu et al., 2009

CgDREBa

Transcription factor

Chrysanthemum

Drought and salinity tolerance

Chen et al.,

GhDREBI

Transcription factor

Arabidopsis

Salt and osmotic tolerance

Huang et al., 2009

Gene

Gene Action

Species

Phenotype

Reference

DREB1A

Transcription factor

Paspalum grass

Salinity and dehydration tolerance

James et al., 2008

DREB1 or OsDREBI

Transcription factor

Rice

Drought, salt and cold tolerance with reduced growth under non-stress

Ito et al., 2006

DREB1A

Transcription factor

Tobacco

Drought and cold tolerance

Kasuga et al., 2004

DREB1A

Transcription factor

Tobacco

Salinity tolerance and dwarfing

Cong et al., 2008

DREB1A

Transcription factor

wheat

Delayed wilting under drought stress

Pellegrineschi et al., 2004

DREB1A; DREB2ATranscription factor

Arabidopsis

Drought-cold tolerance

Maruyama et al., 2009

DREB2A

Transcription factor

Arabidopsis

Drought tolerance

Sakuma et al., 2006

DREB2

Transcription factor

Rice

Improve yield under limited water

Bihani et al., 2011

MbDREBI

Transcription factor

Arabidopsis

Drought and salt tolerance

Yang etal., 2011

SIDREB2

Transcription factor

Foxtail millet

Salinity and osmotic stress resistance

Lata et al., 2011

TaDREB2-3

Transcription factor

Wheat, barley

Drought and frost resistance

Morran et al., 2011

ERA1

Farnesyltransferase

Canola

When down regulated promotes drought tolerance

Wang et al., 2009

FAD3&FAD8

Increased fatty acid desaturation

Tobacco

Drought tolerance

Zhang et al., 2005

FLD

Flavodoxin overexpression

Medicago

truncatula

Salinity tolerance

Pena et al., 2010

FTL1/DDF1

Transcription factor

Arabidopsis

Resistance to cold, drought and heat

Kang et al., 2011

LeGPAT

glycerol-3-phosphate acyltransferase of chloroplasts

Tomato

Salt tolerance

Sun et al., 2010

Gene

Gene Action

Species

Phenotype

Reference

GsCBRLK

Calcium/calmodulin -independent kinase

Arabidopsis

Salt and ABA tolerance

Yang etal., 2010

HAL1

Promote K+/Na+ selectivity

Tomato

Salt tolerance in growth and fruit production

Rus et al., 2001

HAL1

Promote K+/Na+ selectivity

Watermelon

Salt tolerance in growth

Ellul et al., 2003

HAL2

Promote K+/Na+ selectivity

Tomato

Salt tolerance in calli and rooting

Arrillaga et al., 1998

HAL I or HAL II

Promote K+/Na+ selectivity

Tomato

Salt tolerance

Safdar et al., 2011

Hardy

AP2/ERF (APETALA2/ ethylene responsive element binding factors) transcription factor

Clover

Drought and salt tolerance

Abogadallah etal., 2011

HOT2

Encode a chitinase-like protein

Arabidopsis

Salt tolerance

Kwon et al., 2007

Hrf1

Harpin protein

Rice

Drought tolerance via ABA signaling and antioxidants

Zhang et al., 2011

HvCBF4

Transcription factor

Rice

Drought, salt chilling tolerance

Oh et al., 2007

lnsP3

Human type lnositol-(1,4,5) -trisphosphate

Tomato

Drought resistance

Khodakovskaya etal., 2010

ITN1

Transcription factor

Arabidopsis

Salt tolerance

Sakamoto et al., 2008

GmERF3

Jasmonate and ethylene -responsive factor 3

Tobacco

Drought, salt and disease resistance

Zhang et al., 2009

JERF3

Jasmonate and ethylene -responsive factor 3

Tobacco

Salinity tolerance

Wang et al., 2004

SodERF3

Ethylene-responsive factor 3

Tobacco

Drought tolerance

Trujillo et al., 2008

Gene

Gene Action

Species

Phenotype

Reference

JERF1

Jasmonate and ethylene -responsive factor 1

Tobacco

Salinity tolerance

Zhang et al., 2004

JERF1

Jasmonate and ethylene- responsive factor 1

Tobacco

Salt and cold tolerance

Wu eta!., 2007

JERF1

Jasmonate and ethylene- responsive factor 1

Rice

Drought tolerance

Zhang et a!., 2010

JERF1

Jasmonate and ethylene- responsive factor 1

Wheat

Multiple stress tolerance

Xu eta!., 2007

JERF3

Jasmonate and ethylene- responsive factor 3

Tobacco

Drought, salt and freezing tolerance

Wu eta!., 2008

TSRF1

Ethylene-responsive factor 1

Rice

Drought tolerance

Quan et at., 2010

КАРР

Kinase-associated protein phosphatase

Arabidopsis

Salt (Na+) tolerance

Manabe et al., 2008

Iew2

Wilting allele; cellulose synthesis complex

Arabidopsis

Drought tolerance

Chen et al., 2005

LOS5

Regulates ABA biosynthesis

Tobacco

Drought tolerance

Yue et al., 2011

LOS5

Molybdenum cofactor sulfurase (Metabolism of abscisic acid)

Soybean

Drought tolerance

Lief al., 2013.

MCM6

Transcription factor

Tobacco

Salinity tolerance

Dang et al., 2011

NADP-ME2

NADP-malic enzyme

Arabidopsis

Salt tolerance

Liu et al., 2007

MH1

DNA helicase

Arabidopsis

Drought and salt tolerance due to antioxidative action

Luo et al., 2009

MKK9

MAP Kinase

Arabidopsis

Salt tolerance in germination

Alzwiya eta!., 2007

Gene

Gene Action

Species

Phenotype

Reference

GhMPK2

MAP Kinase

Tobacco

Salt and drought tolerance

Zhang et at., 2011

PtrMAPK

MAP Kinase

Tobacco

Drought tolerance

Huang et at., 2011

ZmMKK4

MAP Kinase

Arabidopsis

Salt and cold resistance

Kong et at., 2011

MsPRP2

Transcription factor

Alfalfa

Increased salinity tolerance

Winicov and Bastola 1999

GmNAC11;

GmNAC20

Transcription factors

Arabidopsis

Salt and cold tolerance

Hao et at., 2011

NDPK1

Nucleoside diphosphate kinase 2

Potato

Multiple stress tolerance

Tang et at., 2008

NEK6

NIMA-related kinase

Arabidopsis

Salinity tolerance

Zhang et at., 2011

NFYB2

Transcription factor

Maize

Drought resistance

Nelson et at., 2007

NahG

Salicylate hydroxylase expression

Arabidopsis

Reduced leaf necrosis under salt stress

Borsani et at., 2001

NPK1

Mitogen-activated protein kinase

Maize

Drought resistance of photosynthesis

Shou et at., 2004

OSCDPK7

Transcription factor

Rice

Increased cold salinity and drought tolerance

Saijo et at., 2000

OsCIPKOI-

OSCIPK30

Calcineurin В-like proteininteracting protein kinases

Rice

Salt and drought tolerance

Xiang et at., 2007

OSCIPK03

Calcineurin В-like proteininteracting protein kinase

Rice

Salt tolerance

Rao et at., 2011

CIPK6

Calcineurin В-like proteininteracting protein kinase

Tobacco

Salt tolerance

Tripathi et at., 2009

Gene

Gene Action

Species

Phenotype

Reference

OrbHLH2

helix-loop-helix (bHLH) ncoding gene

Arabidopsis

Salt and osmotic tolerance

Zhu et al., 2009

OsCOIN

RING finger protein

Rice

Cold, salt and drought tolerance and overexpression of P5CS

Liu et al., 2007

OCPI1

Transcription factor

Rice

Drought resistance in yield

Huang et at., 2007

ocp3

Transcription factor

Arabidopsis

Drought resistance

Ramirez et at., 2009

OPBP1

Transcription factor

Tobacco

Salinity and disease tolerance

Guo et at., 2004

OsSbp

Calvin cycle enzyme sedoheptulose-1,

7- bisphosphatase

Rice

Tolerance of photosynthesis to salt

Feng eta!., 2007

OsDREBIA

Transcription factor

Arabidopsis

Drought, salt, freezing tolerance

Dubouz et al., 2003

OSDREB2A

Transcription factor

Rice

Drought tolerance

Cui et a/.,2011

OSMYB3R-2

MYB homeodomain, and zinc finger proteins

Arabidopsis

Drought, salt, freezing tolerance

Dai et al., 2007

OsiSAP8

Stress/zinc finger protein

Rice

Salt drought and cold tolerance

Kanneganti and Gupta, 200

OsNAC5

Transcription factor

Rice

Salt tolerance

Song et al., 2011

OsNACIO

Transcription factor

Rice

Drought tolerance in the field

Jeong et al. 2010

PARP1; PARP2

Poly(ADP-ribose)

polymerase

Arabidopsis;

Brassica

Silencing induces drought and heat tolerance

Block et al., 2004

PDH45

DNA helicase 45

Pea

Salinity tolerance in yield

Sanan-Mishra et al., 2005;

Sahoo et al., 2012

Gene

Gene Action

Species

Phenotype

Reference

PeSCL7

Transcription factor

Arabidopsis

Salt and drought tolerance

Ma et al., 2010

PLD

Phospholipase D

Arabidopsis

Salt tolerance

Bargmann et al., 2009

RGS1

Regulation of G-protein signalling

Arabidopsis

ABA mediated root elongation and drought tolerance

Chen et al., 2006

SCABP8

Interacts with SOS2

Arabidopsis

Salt tolerance

Quan et al., 2007

smGTP

Encode small guanosine triphosphate binding protein

Lolium

temulentum

Salt & dehydration tolerance

Dombrowski et al., 2008

SINAGS1

Ornithine accumulation

Arabidopsis

Drought and salt tolerance

Kalamaki et al., 2009

SIZ1

SUMO E3 ligase

Arabidopsis

Salt tolerance

Miura et al., 2011

SIZ1

SUMO E3 ligase

Arabidopsis

Heat tolerance

Chen et al., 2011

SNAC1

Transcription factor

Rice

Drought and salt tolerance

Hu et al., 2006

TaSnRK2.7

Transcription factor

Arabidopsis

Multi-abiotic stress tolerance

Zhang et al., 2011

ONAC063

Transcription factor

Arabidopsis

Salt tolerance

Yokotani et al., 2009

SQE1

Squalene epoxidase enzyme

Arabidopsis

Root sterol biosynthesis and drought tolerance

Pose et al., 2009

OsRDCPI

Transcription factor

Rice

Drought tolerance

Bae et al., 2011

SRK2C

Protein kinase

Arabidopsis

Osmotic stress/drought tolerance

Umezawa et al.,2004

OsSDIRI

RING-finger containing E3 ligase

Rice

Drought tolerance

Gao et al., 2011

StMYB1R-1

MYB-Like Domain Transcription Factor

Potato

Drought tolerance via reduced water loss Shin eta!., 2011

STO

Protein binds to a Myb transcription factor

Arabidopsis

Salt tolerance

Ngaoka and Takano, 20

Gene

Gene Action

Species

Phenotype

Reference

Sto1

Reduced ABA accumulation

Arabidopsis

Better growth under salt stress

Ruggiero et al., 2004

TaABCI

Protein kinase

Arabidopsis

Drought salt and cold tolerance

Wang et at., 2011

TaCHP

Cysteine, histidine, and proline rich zinc finger protei

Arabidopsis

Promotion of CBF3 and DREB2A expression and salt tolerance

Li etal., 2010

TaPP2Ac-1

catalytic subunit (c) of protein phosphatase 2A

Tobacco

Drought resistance; maintain RWC and membrane stability

Xu etal., 2007

TaSTK

serine/threonine protein kinase

Wheat

Salt tolerance

Ge et a!., 2007

TaSrg6

Transcription factor

Arabidopsis

Drought tolerance

Tong et al., 2007

TERF1

ERF transcription activator

Tobacco

ABA sensitivity and drought tolerance

Zhang et al., 2005

ThlPK2

Inositol polyphosphate kinase

Brassica

Salt and drought tolerance

Zhu et al., 2009

Tsi1

Transcription factor

Tobacco

Increase osmotic stress tolerance

Park et al., 2001

VuNCEDI

Involved in ABA biosynthesis

Creepingbent

grass

Salinity and drought tolerance

Aswath et al., 2005

WAB15

Transcription factor

Tobacco

Freezing, osmotic and salt tolerance

Kobayashi et al., 2008

WIN1/SHN1

Wax inducer

Arabidopsis

Epicuticular wax, stomata number and drought tolerance

Yang etal., 2011

GmWNKI

(With No Lysine K) serine- threonine kinase

Arabidopsis

Seedling salt tolerance

Wang et al., 2011

WRKY25 & WRKY33

Transcription factor

Arabidopsis

Salt tolerance

Jiang and Deyholos, 2009

WRKY45

Transcription factor

Arabidopsis

Drought resistance

Qiu and Yu, 2009

OSWRKY45

Transcription factor

Rice

Drought and cold resistance

Tao et al., 2011

Gene

Gene Action

Species

Phenotype

Reference

AtWRKY63

Transcription factor

Arabidopsis

ABA response and drought tolerance

Ren et al., 2010

WXP1

Epicuticular wax accumulation

Alfalfa

Drought resistance in maintained leaf water status and delayed wilting

Zhang et al., 2005

WXP1

Epicuticular wax accumulation

White clover

Drought resistance

Jiang et al., 2010

WXP1 ;WXP2

Epicuticular wax accumulation

Arabidopsis

Drought and freezing tolerance

Zhang et al., 2007

WRSI5

Protease inhibitors

Arabidopsis

Salt tolerance

Shan et al.,2008

Protease inhibitors

Tobacco

Salt tolerance

Srinivasan et al., 2009

ZmDREB2A

Encodes HSP &LEA proteins

Arabidopsis

Drought and heat tolerance

Qin et al., 2007

ThZFL

zinc finger protein

Tobacco

Salinity tolerance

An eta!., 2011

MtZpt2

zinc finger protein

Medicao

Recover Root growth under salt stress

Merchan et al., 2007

Source: (www.plantstress.com1

Gene

Gene Action

Species

Phenotype

Reference

AIABCG36/

AtPDR8

ATP-binding cassette (ABC) transporter

Arabidopsis

Salt tolerance due to sodium exclusion

Kim et at., 2010

Atchx21

Putative Na+/H+ antiporter

Arabidopsis

Sodium concentrations in plant, root growth, plant size

Hall et ai, 2006

AtCNGCW

Plasma membrane cation transport

Arabidopsis

Salt tolerance

Guo et ai, 2008

AtCLC

Chloride channel

Arabidopsis

Salt tolerance

Jossier et ai, 2010

AtHKTI

Reduction in Sodium in root

Arabidopsis

Salt tolerance

Horie etai, 2006

AtHKTI

Sodium and Potassium transporter

cells

Reduced sodium accumulation

Sunarpi et ai, 2005

GmHKTI

Sodium and Potassium transporter

Tobacco

Salinity tolerance

Chen et ai, 2011

HKT2;1

Sodium and Potassium transporter

Barley

Salinity tolerance

Mian et at., 2011

AtMRP4

Stomatal guard cell plasma membrane ABCC-type ABC transporter,

Arabidopsis

Drought susceptibility due to loss of stomatal control

Markus et at., 2004

AtNHXI

Vacuolar Na+/H+ antiporter

Arabidopsis

Salt tolerance

Yokoi et ai, 2002

AtNHXI

Vacuolar Na+/H+ antiporter

Brassicanapus

Salt tolerance, growth, seed yield and seed oil quality

Zhang et at., 2001

AtNHXI

Vacuolar Na+/H+ antiporter

Buckwheat

Salt tolerance

Chen et at., 2008

AtNHXI

Vacuolar Na+/H+ antiporter

Cotton

Salt tolerance in photosynthesis and yield

He etai, 2005

AtNHXI

Vacuolar Na+/H+ antiporter

Tall fwscue

Salt tolerance

Zhao etai., 2007

Gene

Gene Action Species

Phenotype

Reference

AtNHXI

Vacuolar Na+/H+ antiporter Tomato

Salt tolerance, growth, fruit yield

Apse et al., 1999

AtNHXI

Vacuolar Na+/H+ antiporter Wheat

Salt tolerance for grain yield in the field

Xue et al., 2004

AtNHXI

Vacuolar Na+/H+ antiporter Sugar beet

Salt tolerance, sugar accumulation

Liu et al., 2008

LnNHX2

Vacuolar Na+/H+ antiporter Arabidopsis

K+ accumulation, salt tolerance

Rodriguez-Rosales eta!., 2008

AtNHX5

Vacuolar Na+/H+ antiporter Torenia

Salt tolerance

Shi et al., 2008

AtNHX5

Vacuolar Na+/H+ antiporter Paper Mulberry

Salt and drought resistance

Li eta!., 2011

AtNHX2 AtNHX5

Vacuolar Na+/H+ antiporter Arabidopsis

Salt tolerance

Yokoi et al., 2002

AVP1

Vacuolar H+-pyrophosphatase Arabidopsis (H+-PPase) gene

Salt tolerance in growth and sustained plant water status

Gaxiola et al., 2001

AVP1

Vacuolar H+-pyrophosphatase Alfalfa (H+-PPase) gene

Drought and salt tolerance

Bao et al., 2009

AVP1

Vacuolar H+-pyrophosphatase Agrostis (H+-PPase) gene stolonifera L

Salt tolerance

Li eta!., 2010

AVP1

Vacuolar H+-pyrophosphatase Cotton (H+-PPase) gene

Drought and salt resistance and yield in the field

Pasapula et al., 2011

MdVHPI

Vacuolar H+-pyrophosphatase Tomato (H+-PPase) gene

Drought and salinity resistance

Dong et al., 2011

AVP1 + PgNHXI

H+-PPase + Vacuolar Tomato Na+/H+ antiporter

Salinity tolerance

Bhaskaran & Savithramma 2011

TsVP

H+-PPase gene Cotton

Drought resistance (yield)

Lv et al., 2009

GhNHXI

Vacuolar Na+/H+ Arabidopsis antiporter (cotton)

Salt tolerance

Wu et al., 2004

Gene

Gene Action

Species

Phenotype

Reference

GmCAXI

Cation/proton antiporter

Arabidopsis

Salt tolerance

Luo et al., 2005

HKT1

Potassium transporter

Wheat

Salt tolerance in growth and improved K+/Na+ ratio

Laurie et al., 2002

NtAQPI

PIP1 plasma membrane aquaporin

Tobacco

High root hydraulic conductance and reduced plant water deficit under drought stress

Siefritz et al., 2002

OsARP

Antiporter-regulating protein

Tobacco

Salt tolerance by Na+ compartmentation

Uddin et al., 2006

OsNHXI

Vacuolar Na+/H+ antiporter

Rice

Salt tolerance

Fukuda et al., 2004

OsSOSI

Plasma membrane Na+/H+ exchanger

Rice

Salt tolerance et at., 2007

Martinez-Atienza

SISOS1

Plasma membrane Na+/H+ exchanger

Tomato

Salt tolerance

Olias et al., 2009

PcSrp

Serine rich protein (enhancing ion homeostasis?)

Finger millet

Salt tolerance

Mahalakshmi eta!., 2006

PgTIPI

Tonoplast intrinsic protein

Arabidopsis

Salt tolerance; root dependant drought tolerance

Peng et al., 2007

PpENA1

Plasma membrane Na+ pumping ATPase

Rice

Salt tolerance

Jacobs et al., 2011

PIP1 (VfPIPI)

Plasma membrane aquaporin overexression

Arabidopsis

Faster growth, stomatal closure under drought stress

Cui et al., 2008

PIP1;4 & PIP2;5

Plasma membrane aquaporin overexression

Tobacco

Excessive water loss and retarded seedling growth under drought stress

Jang et al., 2007

Table Contd.

Gene

Gene Action

Species

Phenotype

Reference

TdPIP1;1 or TdPIP2;1

Plasma membrane aquaporin overexression

Tobacco

Salt and osmotic tolerance

Ayadi et al., 2011

SAT32

Enhanced vacuolar H+- pyrophosphatase (H+-PPase

Arabidopsis

Salt tolerance

Park et at., 2009

SITIP2;2

Tonoplast aquaporin

Tomato

Enhanced transpiration and f yield under drought and control

Sade et at., 2009

SOD2

Vacuolar Na+/H+ antiporter

Arabidopsis

Salt tolerance; higher plant K/Na ratio

Gao et at., 2004

SOD2

Vacuolar Na+/H+ antiporter

Rice

Salt tolerance

Zhao et at., 2006

SOS1

Na+/H+ antiporter

Arabidopsis

Protect K+ permeability during salt stress

Qi and Spalding, 2004

SOS3

Sodium accumulation in roots

Arabidopsis

Salt tolerance

Horie et at., 2006

SOS4

Involved in the synthesis of pyridoxal-5-phosphate which modulates ion transporters

Arabidopsis

Salt tolerance through Na+/K+ homeostasis

Shi et at.,2002

SsNHXI

Vacuolar Na+/H+ antiporter

Rice

Salt tolerance

Zhao et at., 2006

SsVP-2

Vacuolar Na+/H+ antiporter

Arabidopsis

Salt tolerance

Guo et at., 2006

TNHX1 and H+- PPase TVP1

Vacuolar Na+/H+ antiporter

Arabidopsis

Salt tolerance

Brini et at., 2007

TaVB

H+-ATPases (V-ATPase) subunit В

Arabidopsis

Salt tolerance

Wang et at., 2011

TsVP

Vacuolar Na+/H+ antiporter

Tobacco

Salt tolerance

Gao et at., 2006

TsVP

Vacuolar Na+/H+ antiporter

Cotton

Salt tolerance

Lv etal., 2008

YCF1

Sequester glutathione- chelates of heavy metals into vacuoles

Arabidopsis

Heavy metal and salt tolerance

Koh et at., 2006

Source: (www.plantstress.com)

2004; Pellegrineschi et al, 2004; Behnam et al., 2006; Bhatnagar-Mathur et al, 2004, 2006). The use of stress inducible rd29A promoter minimized the negative effects on plant growth in these crop species. However, over expression of DREB2 in transgenic plants did not improve stress tolerance, suggesting involvement of post-translational activation of DREB2 proteins (Liu et al, 1998). Recently, an active form of DREB2 was shown to trails activate target stress-inducible genes and improve drought tolerance in transgenic Arabidopsis (Sakuma et al., 2006). The DREB2 protein is expressed under normal growth conditions and activated by osmotic stress through post-translational modification in the early stages of the osmotic stress response. Another ABA-independent, stress-responsive and senescence-activated gene expression involves ERD gene, the promoter analysis of which further identified two different novel cis acting elements involved with dehydration stress induction and in dark-induced senescence (Simpson et al., 2003). Similarly, transgenic plants developed by expressing a drought-responsive AP2- type TF, SHNl-3orWXPl, induced several wax-related genes resulting hi enhanced cuticular wax accumulation and increased drought tolerance (Aharoni et al., 2004; Zhang et al., 2005). Thus, clearly, the over expression of some drought-responsive transcription factors can lead to the expression of downstream genes and the enhancement of abiotic stress tolerance in plants (see review, Zhang et al., 2004). The regulatory genes/factors reported so far not only playa significant role in drought and salinity stresses, but also in submergence tolerance. More recently, an ethylene response-factor-like gene SublA, one of the cluster of three genes at the Subl locus have been identified in rice and the over expression of SublA-1 in a submergence-intolerant variety conferred enhanced submergence tolerance to the plants (Xu et al.,2006),thus confirming the role of this gene in submergence tolerance in rice.

 
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