The role of chloroplasts in responding to drought stress in plants

Food security is a major problem facing the World and one that is going to become more pressing in coming decades due to increased population and new challenges imposed by climate change (1). With a limit on irrigation, much of the estimated 50% increase in productivity required by 2030 will need to come from rain-fed agriculture and thus drought is the major abiotic stress limiting crop yields worldwide. Since photosynthesis is so sensitive to the environment, the chloroplast plays a central role in the response of plants to environmental stresses including drought. For drought stress, there is an increasing body of evidence that enhancement of the chloroplast-localised tetrapyrrole pathway through treatment with tetrapyrrole precursors can protect plants (2). Although the mechanism is not well understood, heme synthesis is suggested to be the critical factor. Heme is also a key player in communication between the chloroplast and nucleus (3) and our own transcriptomic results show some overlap between retrograde- and drought-responsive genes. In this project we will test the hypotheses that activation of chloroplast-to-nucleus retrograde signalling protects against drought and that drought modifies the chloroplast proteome to bring about these changes in retrograde signalling.