Identification of genes involved in carbon metabolism from Eleusine coracana (L.) for understanding their light-mediated entrainment and regulation.

KEY MESSAGE: The study would be helpful in understanding the synchronization of genes of a pathway and its effect on carbon metabolism which can be further utilized for better agronomic performance. Finger millet (Eleusine coracana) is a C4 crop with high nitrogen use efficiency (NUE) said to be organic by default. Being carbon and nitrogen mutually exclusive, in the present study, it was investigated how light regulates the expression of genes of carbon metabolism and photosynthesis in two finger millet genotypes (GE 3885 and GE 1437) with differing grain protein content (13.8 and 6.2%). Different genes associated with carbon metabolism were isolated (Cab, RBCS, PEPC, PPDK, PEPC-k, ME, SPS, PK, 14-3-3 and SnRK1) and the co-expression of Dof1 and these genes was investigated under different light-dark conditions. The deduced protein sequences of isolated genes showed relationship of marked variations with their homolog which might corresponds to difference in photosynthetic efficiency between finger millet and other plants. In 24 h day-night conditions, the identified genes exhibited diurnal rhythm in both genotypes with different time of peak expression. In dark, the expression of identified genes in both genotypes oscillated with varied amplitude indicating their control by an endogenous clock. However, Cab, RBCS and PPDK showed no oscillations suggesting that genes are light inducible. Exceptionally, ME transcript showed differential response within genotypes. Upon illumination, genes were induced within the measured period indicating that light is a signal involved in the entrainment of these genes. Exception was ME and SnRK1 in GE 1437. We conclude that expression of Dof1 in higher grain protein genotype was more consistent with the expression of carbon metabolism genes under study suggesting that Dof1 differentially regulates the expression of these light inducible genes and simultaneously controls the grain protein content in finger millet genotypes.