Abstract
Bacterial wilt (BW) is a soil-borne disease that severely impacts plant growth and productivity globally. Ubiquitination plays a crucial role in disease resistance. Our previous research indicated that NAC transcription factor SmNAC negatively regulates BW resistance in eggplant (Solanum melongena). However, whether the ubiquitin/26S proteasome system (UPS) participates in this regulation is unknown.
This study used SmNAC as a bait to screen eggplant cDNA library and obtained SmDDA1b, an E3 ubiquitin ligase. Subcellular location and bimolecular fluorescence complementation assays revealed that SmDDA1b could interact with SmNAC in the nucleus. The in vivo and in vitro ubiquitination experiments indicated that SmDDA1b can degrade SmNAC through UPS. However, the discovery of negative regulation of SmDDA1b expression by SmNAC showed that there was a negative feedback loop between SmNAC and SmDDA1b in eggplant.
The SmDDA1b-overexpressed lines showed a higher BW resistance associated with high expression levels of salicylic acid (SA)-related genes and SA content than the wild-type lines. However, SmDDA1b-silencing lines showed the opposite results, indicating that SmDDA1b is a positive regulatory gene for BW resistance.
This study provides a candidate gene that can enhance BW resistance in eggplants. In addition, it provides insight into a mechanism that promotes plant disease resistance via the SmDDA1b-SmNAC-SA pathway.
Footnotes
E3 ubiquitin ligase degrades the negative regulator of SA synthesis and enhances plant disease resistance.
↵1 Y.W., S.Y. and B.Y. performed the research; B.C., Z.Q. and J.L. designed the research; C.C., Y.G. and Z.Z. provided new reagents; Y.W. and B.Y. analyzed the data; and Y.W., Z.Q. and B.C. wrote the manuscript.
The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (https://academic.oup.com/plphys/pages/general-instructions) is: Zhengkun Qiu (qiuzhengkun{at}scau.edu.cn) and Bihao Cao (caobh01{at}163.com).
This research was funded by the Key Project of Guangzhou (202103000085), Fruit and Vegetable Industry System Innovation Team Project of Guangdong (2021KJ110), and the National Natural Science Foundation of China (31672156).