The antagonistic role of GA and ABA in the control of the switch between dormancy and germination is a well known mechanism. however Ruxolitinib the function of these hor mones during the early stages of seed development remains unclear. Our data suggest that there is miRNA regulation of ABA and GA signalling during the early stages of grain development, with degradome analysis identifying two ABA Insensitive homolog genes, a GA3oxidase1 and a homolog of the GA re ceptor Inhibitors,Modulators,Libraries GID1 as targets of miRNAs or pot miRNAs. ABI3 is cleaved with a perfect offset by 2 members of the grass specific miRNA family hvu miR516. Degradation products of ABI3 only accumulate during stage C whereas the corre sponding miRNAs are expressed earlier. In contrast, the cleavage of GID1 mostly occurs during early stages while the cognate pot miRNAs accumulate in later stages.

This suggests that in both cases the miRNAs Inhibitors,Modulators,Libraries could act to pre vent leakage in target gene expression, ensuring that GID1 function is restricted to early stages and ABI3 to later stages. These data support the current belief that GA is required during early embryogenesis but its func tion is repressed in later phases when a higher ABA GA balance is needed for the proper maturation of the grain. This also correlates with the observation that the late presence of GA may inhibit embryogenic cell differenti ation. Our data also suggest that there is miRNA regulation of ethylene responses with an ACC oxidase homolog cleaved by a pot miRNA during the early maturation phase.

Along with ABA, ethylene is thought to play a major role in the development of the endosperm by affecting grain filling and the timing of programmed cell death. Defence response Plants recognize many pathogens through the action of a diverse family of R genes, whose protein products are necessary for the direct or indirect recognition of patho Inhibitors,Modulators,Libraries gen avirulence proteins in order to initiate the de fence response. In addition to their role in defence responses, R genes may be involved in the regulation of developmental processes in Arabidopsis and rice. In barley, the R gene MLA10 acts as a receptor of fun gal infection by recognising avirulence proteins and con fers resistance against the powdery mildew fungus. In wheat the expression of several miRNAs is re sponsive to powdery mildew infection, suggesting that the miRNA pathway could be involved in triggering Inhibitors,Modulators,Libraries the defence response.

Our degradome analysis indicates that two HvMLA genes homologous to the rice MLA1 and MLA10 genes are cleaved by miRNAs or pot miRNAs. Further investigation of OsMLA10 like and GA3oxidase1 regulation The impact of regulation by a miRNA depends on the relative spatio temporal accumulation Inhibitors,Modulators,Libraries of the miRNA and the target mRNA. In this study, we focused Epigenetic Reader Do on in vestigating miRNA regulation at three consecutive stages of grain development.