Mitochondria-Chloroplast Cross Talk: A Possible Role for Calcium and Reactive Oxygen Species?

One of the major challenges for plant biology research is to elucidate the complex mechanisms involved in the plant response to stress conditions. This is of utmost importance in view of climatic change that affects crop yields, because of exposure of plants to more severe and frequent environmental stresses such as drought, salinity, and high light. The defense response of the plants to stress conditions requires the orchestration among different signaling pathways activated in different subcellular compartments. An increasing knowledge became available about the role of bioenergetics organelles, the sites of energy conversion in eukaryotes by photosynthesis in chloroplasts and respiration in mitochondria. Information is mainly restricted to retrograde signaling between the organelles and the nucleus. The emerging hypothesis discussed in this minireview is that interorganellar cross talk between mitochondria and chloroplasts through Ca2+ and reactive oxygen species signaling may also play a role in ensuring an optimized response of plants and algae to environmental stresses.