AtDJB3, a J-domain protein, regulates seed amyloid accumulation and ABA-mediated early developmental transition in Arabidopsis thaliana.

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conclusionOur study shows that AtDJB3 modulates seed amyloid-like protein assemblies to regulate ABA sensitivity, thereby coordinating germination and early seedling development, and shaping adaptive responses during early plant growth. Molecular chaperones are highly abundant in seeds, yet their roles during the transition from seed to seedling remain poorly defined. In this study, we identify AtDJB3, an aggregate-remodeling J-domain protein (JDP), as a regulator of abscisic acid (ABA)-mediated responses during early developmental transitions in Arabidopsis thaliana. AtDJB3 expression is induced by ABA and depends on the transcription factors ABI3 and ABI5 during germination. A T-DNA insertion mutant of AtDJB3 (atdjb3-1) exhibited enhanced germination but impaired post-germinative growth in the presence of ABA compared to wild-type plants, indicating a role for AtDJB3 in fine-tuning ABA responses across distinct developmental phases. Consistently, atdjb3-1 seeds showed improved radicle emergence and cotyledon opening under osmotic stress, often associated with ABA-mediated growth inhibition. Notably, dry atdjb3-1 seeds accumulated elevated levels of amyloid-like protein assemblies, linking altered aggregate remodeling to the observed changes in ABA-regulated seed-to-seedling progression. Together, these findings implicate AtDJB3 as an important component of the ABA signaling network that coordinates developmental timing and stress adaptation in A. thaliana.