Regulation of developmental transitions in plants: the role of VIVAPAROUS ABI3-LIKE (VAL) repressors.

During its lifetime, the plant undergoes transitions between critical developmental stages, such as seed-to-seedling and adult-to-flowering stages. The changes between stages are strictly controlled by genetic and epigenetic factors that act together during the transition. The developmental transition involves repressing active genes in the first stage and activating genes in the next stage. Thus, repression appears to be essential for terminating the previous developmental program, and among the repressors, the VAL genes play a central role. The VALs are B3-domain DNA-binding proteins that regulate LAFL genes during the seed-to-seedling transition, during which VALs downregulate LAFL expression, thereby terminating the embryogenic program in seedlings. Moreover, the VAL also affects the expression of MIR156C, FLC, or FT in the regulation of flowering. These proteins interact with numerous chromatin remodeling factors, such as PRC1, PRC2, and HDAC, which perform distinct histone modifications, ubiquitination, methylation, or deacetylation to negatively regulate the expression of target genes. This review examines the recent advances in studies on the VALs genetic network, which is involved in the developmental transition via diverse epigenetic mechanisms. Moreover, a future perspective on studies of these essential regulators was discussed.