A Systems Approach to Investigate the Role of Source-Sink Communications in Senescence in Maize

Accumulation and partitioning of carbohydrates (CHO) affects all aspects of grain and biomass yield in grasses and, therefore, strategies to improve yield aim to improve one or both of these processes. Senescence, a highly regulated process involving degradation of cellular components, lies at the interface of both these processes. Senescence is affected by the source-sink dynamics of CHO partitioning and reduces CHO accumulation by disrupting photosynthetic assimilation. We are using a systems approach to identify genetic, molecular, and biochemical mechanisms underlying the regulation of senescence in maize. We have characterized natural genetic variability for developmental senescence and senescence induced by the absence of grain sink in maize and identified candidate genomic regions harboring genetic elements that govern senescence. To complement the genomic approaches, we have generated leaf transcriptome of plants of B73 inbred undergoing premature senescence due to absence of grain sink using RNA-sequencing. Transcriptomic data and genetic analyses of isogenic lines derived from B73 and Mo17 were used to further corroborate the candidate genes/regions identified through genomic approaches. We are currently working on cloning and characterizing genes underlying endogenous variation in the onset of senescence. Identification of genetic and molecular mechanisms governing senescence will provide avenues for devising and implementing strategies to optimize photosynthate partitioning and enhance overall carbohydrate yield without a significant increase in agricultural inputs.