Photosynthesis, a global sensor of environmental stress in green plants: stress signalling and adaptation

Photosynthesis serves as a global stress sensor in plants, algae and cyanobacteria. In this overview, we focus on higher plants only. Although several structural and functional components of the photosynthetic apparatus are responsive to stress, photosystem II (PS II) and ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco) act as the major stress sensors. Stress sensing is primarily reflected in cellular energy imbalance, which, in this review, is discussed in terms of perturbation in photostasis, imbalance in redox homeostasis and changes in cellular sugar level. Signals generated by these changes bring about photochemical, metabolic and molecular reprogramming for stress adaptation through different signal transduction pathways. Recent redox and sugar signalling models, which explain stress response of green plants, are discussed here. This review concludes with a brief description of some of the challenging and unresolved areas of stress study, which we hope would be addressed in the near future.