西北农林园艺学院王晓峰教授团队近日在《The Plant Cell》期刊发表了题为Brassinosteroid Receptor StBRI1 Promotes Tuber Development by Enhancing Plasma Membrane H+-ATPase Activity in Potato的研究论文，揭示了BR信号通过StBRI1-PM H+-ATPase（PHA2）单元模块调控马铃薯块茎形成的分子机制，这些结果对于马铃薯高产分子育种具有一定的理论价值。 博士生邓瑞和陕西省杂交油菜研究中心黄淑华副研究员为本论文共同第一作者，王晓峰教授为本论文通讯作者。
The plant hormone brassinolide (BRs) is widely present in various plant tissues, and its key role is reflected in the regulation of cell expansion and differentiation processes and seed formation. BRI1 is the core receptor of brassinolides (BRs). It is not only an indispensable part of plant hormone signal transduction, but also has the ability to directly sense BRs and regulate plant growth and development accordingly.
Potato (Solanum tuberosum), an annual herb of the Solanaceae family, is the staple food of 1.3 billion people worldwide. In agricultural production practice, the exogenous application of brassinolide (BRs) has been proven to be effective in increasing the number of tubers and yield per plant, thereby increasing the total potato yield. However, the molecular mechanism of how BR signaling regulates potato tuber development remains unclear. In addition, the activity of PM H+-ATPase in plants was also affected by a variety of factors. Little is known about the specific components of how BR signaling regulates PM H+-ATPase phosphorylation levels. There is also a lack of sufficient evidence to confirm whether BRI1 precisely regulates PM H+-ATPase activity through phosphorylation modifications.
In this study, potato was taken as the research object, and knockout of potato StBRI1 hindered potato tuber formation. In order to verify the role of StBRI1 in regulating potato tuber development, the 35S promoter was used to control the expression of StBRI1. Transgenic plants had higher plant height and internode length than wild-type plants, and the number of tubers and tuber yield were significantly increased. In addition, by fusing the B33 tuber-specific promoter to drive StBRI1 (ProB33:StBRI1-GUS), it was found that the tuber yield of transgenic plants was also significantly increased, and the number of tubers was higher than that of the wild type. Studies have shown that StBRI1 positively regulates potato tuber development by increasing the number of tubers, weight, and cell size (Figure 1).
Fig.1 StBRI1 positively regulated potato tuber development
Combined with genetic evidence, Co-IP analysis and PM H+-ATPase activity assays using dual transgenic lines, as well as a series of biochemical experiments, showed that StBRI1 interacted with the C-terminus of PHA2, which inhibited the intramolecular interaction between the C-terminus of PHA2 and the central ring of PHA2, thereby attenuating the autoinhibition of PM H+-ATPase activity, resulting in an increase in PHA2 activity, and that PHA2 may be downstream of StBRI1 to exert its function. Further studies showed that overexpression of PHA2 in potatoes increased tuber weight, starch content and cell area, while inhibition of PHA2 expression decreased these indicators. The Thr-951 residues of PHA2 were mutated to the simulated phosphorylated form (D) and non-phosphorylated form (A), respectively, and the 35S promoter-driven PHA2-T951A and PHA2-T951D transgenic potato plants were constructed. StBRI1 and PHA2 were found to be closely related to cell growth and proton pump activity (Figure 2).
Fig.2 StBRI1 promotes tuber development by affecting phosphorylation of PHA2
In conclusion, activated StBRI1 inhibits its internal intermolecular interactions by phosphorylating the penultimate Thr-951 residue at the C-terminus of the proton pump in the presence of BR. As a result, the proton pump is activated, which promotes BR-mediated cell expansion and tuber development, resulting in improved tuber yield (Figure 3). The results of this study showed that the BR-StBRI1-PHA2 module regulates tuber development, indicating that the strategy based on the BR signaling pathway on the cell surface has certain application prospects for improving the growth and yield of tuber crops.
BR-StBRI1-PHA2促进块茎发育的理论模型
The research was funded by the National Natural Science Foundation of China.
Original link: https://doi.org/10.1093/plcell/koae163
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