Professor University of Nevada Las Vegas Las Vegas, Nevada
Body of Abstract: Tremendous progress has been made in addressing the mechanism controlling seed dormancy and germination; however, studies of germination speed control are still rare. OsWRKY71 is one of the Group IIa WRKY genes, which emerged at the same time as the appearance of seeds and more complex defense responses. Our previous studies using particle-bombardment-mediated transient expression indicate that OsWRKY71 and its barley ortholog modulate abscisic acid (ABA) and gibberellin (GA) signaling in rice and barley aleurone cells. However, genetic, transcriptomic and metabolomic evidence still needs to be provided regarding if and how this gene controls seed germination. Here we demonstrate that two oswrky71 mutants germinate 30-38% faster than wildtype. Both embryo and aleurone cells, which are hyposensitive to ABA, contribute to the phenotype. Comprehensive transcriptomic profiling of the mutants suggests that OsWRKY71 is a master regulator of transcription, controlling the expression of 9-17% of genes in dry and germinating embryos. Among these are critical ABA signaling and dormancy promoting genes. Interestingly all these genes are induced, rather than repressed, after germinating embryos pass a newly defined critical check point of seed germination. We propose that OsWRKY71 negatively regulates germination before this check point and then switches to other roles including negatively regulating defense responses once the check point is passed. Association studies revealed that OsWRKY71 is likely a primary gene of QTLs involved in seed germination speed control under cold conditions. For risk assessment of the mutant seeds for human consumption, we performed metabolomic analysis along with standard analytical methods for grain nutrient contents and identified differential metabolites between the wild type and oswrky71 mutants. It is possible that orthologues of OsWRKY71 in other crops can be knocked out using CRISPR to produce fast-germinating seeds for the improvement of both dicot and monocot crops e.g. maize, wheat, barley and soybean.