Open questions on ROS Coupling in Nonlinear Systems
The enormous work performed during the last decades has clarified the deleterious effects of ROS on photosynthetic organisms. However, this is only one side of ROS functions. The other side is the very important signaling role of ROS in the response of cyanobacteria, alga and higher plants to different forms and conditions of stress. In spite of significant progress achieved during the last decade, our current state of knowledge on this topic is still rather fragmentary.
There are several questions that need to be answered:
- 1. How do ROS generated in chloroplasts affect the transcription of the chloroplast genome?
- 2. How can ROS leave the chloroplasts and directly induce a significant expression of genes of the nuclear genome?
- 3. What is the nature and the mechanistic function of second messengers formed by reaction of ROS with specific molecules like lipids and Cars?
- 4. What determines the mechanism of ROS wave propagation in plant cells?
- 5. What is the identity of the primary sensor(s) of ROS (transcription factors and/or protein kinases) and the primary genes responding to oxidative stress?
- 6. Do ROS induce new signaling pathways by acting as second messengers?
Significant progress in answering these questions is expected from the development of new spectroscopic methods for monitoring ROS, in particular with high spatial resolution, and their application in combination with directed genetic engineering of plants. Among the methods for manipulations at molecular level the targeted ROS production within specific cell compartments and organelles is of high interest.
One important approach towards exploitation of photosynthetic organisms as sustainable sources of biomass is the improvement of the resistance of the cells against environmental stress conditions. This problem targets world food and world energy supply. On the other side plants function as sensitive indicators for the environmental conditions and photosynthetic activity changes in contact to diverse dust pollutants leading to dynamic changes of chlorophyll fluorescence. The full understanding and technical exploitation of these mechanisms has implications on food production. It additionally opens the way to develop rapid alert systems for dust pollutants or, more generally, as reporters for the environmental quality, by monitoring the fluorescence properties of plants like for example lichens (e.g. Peltigera aphtosa) which are sensitive to pollutants (Maksimov et al., 2014b).
As the World Health Organization (WHO) just recently pointed out air pollution as the worst environmental threat for human and environmental health, the need for techniques to quantify the air contamination and its impact on plants is pressing. The WHO estimates that seven million people worldwide died due to illnesses linked to air pollution in 2012 alone, according to new data released on March 25th 2014. These shocking developments urgently require new techniques and initiatives that are able to quantify the air pollution and might help to decontaminate air especially in the big cities. Plants with selected and specialised properties might be a solution for these problems.
The genetic transformation of plants according to a deep molecular biological knowledge of all processes that interact with ROS delivers a tool to produce enhanced plants as ROS sensors, ROS scavengers or crop plants with improved resistance to ROS. The analyses of the capability of cyanobacteria and algae for the decontamination of water and air give rise to genetically enhanced ROS scavengers.