Towards the end of their life span, most plant leaves turn yellow, a highly visual process known as senescence. Senescence in annual crops is a gradual process, which starts with older leaves and, in cereals, progresses from the leaf tip towards the base. Its importance stems from the fact that a large fraction of the nutrients present in green leaves are remobilized from senescing leaves and retranslocated to surviving structures, such as seeds of annual plants. At present, the biological processes controlling senescence are incompletely understood. This project focuses on a particular gene (coding for a glycine-rich RNA-binding protein, or GRP), which is highly upregulated in leaves of early- as compared to late-senescing barley lines. The biological function of GRP in the control of leaf senescence will be investigated using a combination of physiological, molecular and biochemical approaches. Specifically, the investigators will (1) determine how the control of leaf senescence by GRP is influenced by plant developmental stage (comparing gene function before and after flowering occurs); (2) use a modern molecular biology approach to silence the GRP gene to compare leaf senescence in control plants with plants with reduced gene function; and (3) determine the three-dimensional structure of GRP, a common approach to advance our understanding of protein biological function. The investigators anticipate that this multi-pronged approach will substantially improve our understanding of GRP function in the control of cereal leaf senescence. Gained knowledge will be applicable to the development of crops with improved nutrient (fertilizer) use efficiency, higher quality (higher grain protein from nitrogen remobilization), and possibly higher yield (later senescence could lead to longer green leaf duration and photosynthetic carbon dioxide assimilation). This project will also provide training opportunities for two postdoctoral research associates and a graduate student.
