RING‐type E3 ligase BnaJUL1 ubiquitinates and degrades BnaTBCC1 to regulate drought tolerance in Brassica napus L

Abstract Drought stress poses a persistent threat to field crops and significantly limits global agricultural productivity. Plants employ ubiquitin‐dependent degradation as a crucial post‐translational regulatory mechanism to swiftly adapt to changing environmental conditions. JUL1 is a RING‐type E3 ligase related to drought stress in Arabidopsis . In this study, we explored the function of BnaJUL1 (a homologous gene of JUL1 in Brassica napus ) and discovered a novel gene BnaTBCC1 participating in drought tolerance. First, we utilised BnaJUL1‐cri materials through the clustered regularly interspaced short palindromic repeats (CRISPR)‐CRISPR‐associated protein 9 system. Second, we confirmed that BnaJUL1 regulated drought tolerance through the drought tolerance assay and transcriptome analysis. Then, we identified a series of proteins interacting with BnaJUL1 through yeast library screening, including BnaTBCC1 (a tubulin binding cofactor C domain‐containing protein); whose homologous gene TBCC1 knockdown mutants ( tbcc1‐1 ) exhibited ABA‐sensitive germination in Arabidopsis , we then confirmed the involvement of BnaTBCC1 in drought tolerance in both Arabidopsis and Brassica . Finally, we established that BnaJUL1 could ubiquitinate and degrade BnaTBCC1 to regulate drought tolerance. Consequently, our study unveils BnaJUL1 as a novel regulator that ubiquitinates and degrades BnaTBCC1 to modulate drought tolerance and provided desirable germplasm for further breeding of drought tolerance in rapeseed.