Shade avoidance is a critical adaptive strategy employed by plants to respond to competition. N6-methyladenosine (m6A), the most abundant and dynamic mRNA modification, has emerged as a key epigenetic mechanism regulating adaptive responses. Here, we demonstrate that shade significantly reduces global m6A levels in a manner dependent on phytochrome B (phyB) and the m6A methyltransferase complex (MTC). Shade attenuates the interaction between phyB and the MTC, impairing the RNA-binding capacity and methyltransferase activity of the complex. Transcriptome-wide m6A profiling showed that shade and phyB mutation similarly reduce m6A modifications, particularly on transcripts involved in auxin and abscisic acid (ABA) signaling pathways. Phenotypic analysis confirmed that the MTC is essential for shade-induced hypocotyl elongation and ABA hypersensitivity. Mechanistically, shade-induced m6A reduction increases the stabilization of SAUR15/19/20 transcripts and decreases the translation efficiency of ABA signaling repressors SNZ, MYB20, and PROPEP3. Our findings reveal a mechanism by which phyB modulates m6A deposition to fine-tune plant elongation and stress adaptation under shade.
Li et al. (Sun,) studied this question.