Regulation of Shade Avoidance Under Low-Blue-Light by MTA in Soybean.

Under low blue light (LBL) conditions, soybean exhibits classic shade avoidance syndrome (SAS) with exaggerated stem elongation (ESE), leading to lodging and yield reduction in dense farming. Recently, mRNA modification by N6-methyladenosine (m6A) has emerged as a crucial epigenetic mechanism regulating plant biological processes; however, its impact on shade avoidance remains unexplored. In this study, the double mutants, gmmtas, that are impaired in two mA writer genes, GmMTAa and GmMTAb that encode mA methyltransferases or mA writers are generated. It is found that the gmmtas mutants showed a substantial reduction of m6A levels, a dwarf phenotype, and a diminished sensitivity to LBL. Further investigation of the gmmtas mutants demonstrates that GmMTA regulates shade avoidance response by altering the expression of GmCRY1s, GmSPAs, and GmCOP1s, resulting in increased accumulation of GmSTFs that are known to suppress the shad avoidance response in response to LBL in soybean. The findings reveal a novel molecular mechanism regulating shade resistance in soybean, providing insights into the epigenetic mechanisms of plant adaptation to changing light environments and paving the way for the development of shade-tolerant soybean varieties.