Autophagy-related genes AtATG5 and AtATG7 influence reserve mobilization and ABA responses during Arabidopsis seed germination

Autophagy, a conserved intracellular recycling pathway, operates both non-selectively and through targeted degradation. In this study, we assess its role in Arabidopsis thaliana seed biology by examining loss-of-function mutants of ATG5 and ATG7 and their interaction with ABA signaling. Both atg5 and atg7 seeds display delayed germination relative to Col-0, an effect that is exacerbated by ABA. Histochemical staining reveals altered organization of lipid droplet and protein storage vacuole (PSV) organization in the mutants, and ATG8 fail to localize to PSVs when autophagy is impaired. Transcriptome profiling of atg7 seeds particularly under ABA treatment reveals substantial shifts in gene expression, with approximately 22 % of ABA-responsive differentially expressed genes. In wild-type seeds, ABI5 protein levels decline after imbibition; this process is delayed in atg mutants, which also accumulate higher levels of the ABI5 homolog bZIP67. Yeast two-hybrid (Y2H) and co-immunoprecipitation assays support a functional association between ATG8 and ABI3/ABI5 transcription factors, direct or indirect, consistent with a link between autophagy and ABA signaling. Collectively, our data support a role for autophagy in reserve mobilization during seed germination and suggest that autophagy contributes to the control of transcriptional networks associated with ABA responses.