The ancestral form of cultivated barley produces two rows of grain along the grain bearing 'spike'. However, types with six rows of grain emerged soon after the domestication of the species and quickly became the dominant form in primitive agricultural systems. This morphological and developmental switch is generally accepted to result from recessive mutations in a single gene called SIX-ROWED SPIKE 1 (VRS1). However alleles at several other SIX-ROWED SPIKE genes have since been identified and shown to interact with VRS1 to enhance the six-row phenotype. The appearance of six-rowed types provided a major yield enhancement in early agriculture and although the gap between two- vs. six. row types has narrowed through breeding, it is clear that considerable potential remains for exploiting the development of up to three times as many grains per inflorescence as a route towards increasing yield. In this project I will take a novel approach in a crop plant to understand how this switch is elaborated. I propose using Laser-Capture Microdissection of the group of cells that initiate the development of fertile lateral florets, coupled with RNA-seq of the resulting tiny RNA samples. I will compare the obtained transcript profiles over developmental time from a pair of nearly isogenic lines that differ only for VRS1 (i.e. Vrs1/vrs1), thus avoiding any genetic background noise. I will use the comparative data to identify differentially expressed genes and the time series data to investigate the network of interactions that promote this characteristic switch between infertile and fertile inflorescence. Finally, I will initiate the production of transgenic knockdown plants to explore the functional effects of some of the identified genes on inflorescence development. In the process I will learn a range of new approaches, techniques and skills that will help ensure I am well placed for an independent career in the field of crop plant genetics.
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