Vacuole formation in the female gametophyte

Hu and Yu et al. demonstrate that BIN2-VLG module regulates vacuole formation in female gametophyte.

By Li-Qin Hu, Shi-Xia Yu, and Wen-Hui Lin

Background: In Arabidopsis, the development of the female gametophyte (FG) within the ovule is essential for plant reproduction and seed yield. Formation of the large vacuole within the FG is required for FG expansion, nuclear polar localization, and cell fate determination, which is critical for successful double fertilization. Generally, the large vacuole is visible after the first nuclear division during FG development. VACUOLELESS GAMETOPHYTES (VLG) regulates FG development by facilitating vesicular fusion to form large vacuole, but how VLG is regulated in this process remains unclear.

Question: How does the spatiotemporal formation of the large vacuole influence Arabidopsis FG development? How is VLG function regulated during FG development?

Findings: BRASSINOSTEROID INSENSITIVE2 (BIN2) is expressed in the FG and localizes in vesicular-like structures. Increased BIN2 activity (in the gain-of-function mutant bin2-1) enhances VLG stability through preventing its degradation by the 26S proteasome; the increase in VLG promotes large vacuole formation at stage FG1. Decreased BIN2 activity (in the loss-of-function mutant of BIN2 and its homologs bin2-3 bil1 bil2) reduces VLG stability, which decreases vacuole formation at stage FG2. Both conditions impair FG development. Overall, our study revealed that the spatiotemporal formation of large vacuoles regulated by the BIN2-VLG module is required for normal FG development.

Next steps: Further studies will elucidate mechanisms by which early formation of the large vacuole disturbs nuclear division and FG development. We speculate that it changes the condition of organelles and micro-environment of the functional megaspore at stage FG1. So, we will further study how the first nuclear division of FG is affected. This work could contribute to understanding how FG development is triggered after the functional megaspore formed.

Reference:

Li-Qin Hu, Shi-Xia Yu, Wan-Yue Xu, Song-Hao Zu, Yu-Tong Jiang, Hao-Tian Shi, Yan-Jie Zhang, Hong-Wei Xue, Ying-Xiang Wang and Wen-Hui Lin. (2023). Spatiotemporal formation of the large vacuole regulated by the BIN2-VLG module is required for female gametophyte development in Arabidopsis. https://doi.org/10.1093/plcell/koad007