DREB2B negatively regulates <i>Arabidopsis</i> and cotton seed vigor through an abscisic acid-mediated pathway

Seed vigor is an important trait ecologically, agronomically, and economically, and is controlled by manifold genetic and exogenous factors. Dehydration-responsive element-binding protein 2B (DREB2B), a subgroup of the DREB transcription factor family, is well-known for conferring multiple abiotic stress resistance. However, the role of DREB2B in seed vigor has not been identified. Here, DREB2B was identified as a negative regulator of seed vigor using a loss-of-function mutant, gene editing, and over-expressing transgenic lines studies in Arabidopsis and Gossypium spp. The lower and higher sensitivity of loss-of-function mutants and overexpression lines of DREB2B to abscisic acid (ABA) and fluridone, respectively, emphasized the negative roles of DREB2B in seed vigor and germination via the ABA-mediated pathway. Further genetic and molecular analyses revealed that DREB2B exhibits both synergistic and independent functions in regulating seed germination and vigor concerning ABA INSENSITIVE 3 (ABI3). We observed that DREB2B formed transcriptional complexes with Radical-Induced Cell Death1 (RCD1) and Similar to RCD One 1 (SRO1) to regulate seed germination and vigor. In addition, RNA-seq analysis of dreb2b and rcd1-3 lines indicated that DREB2B and RCD1 may target the same pathways in seed germination and vigor associated with ABA accumulation modification, which is supported by DREB2B directly regulating ABA DEFICIENT 2 (ABA2) promoter activity. Collectively, these results suggest that ABA-mediated complexes consisting of DREB2B, RCD1, SRO1, and ABI3 function upstream of ABA2 to negatively regulate seed vigor in plants, expanding on our knowledge of seed development.