Liu Xiaoyan, Nakajima Kohdai P, Adhikari Prakash Babu, Wu Xiaoyan, Zhu Shaowei, Okada Kentaro, Kagenishi Tomoko, Kurotani Ken-Ichi, Ishida Takashi, Nakamura Masayoshi, Sato Yoshikatsu, Kawakatsu Yaichi, Xie Liyang, Huang Chen, He Jiale, Yokawa Ken, Sawa Shinichiro, Higashiyama Tetsuya, Bradford Kent J, Notaguchi Michitaka, Kasahara Ryushiro D
School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China; FAFU-UCR Joint Center and Fujian Provincial Key Laboratory of Haixia Applied Plant Systems Biology, Haixia Institute of Science and Technology, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China.
Department of Biology, Technion-Institute of Technology, Haifa 320000, Israel.
Curr Biol. 2025 May 5;35(9):2049-2063.e3. doi: 10.1016/j.cub.2025.03.033. Epub 2025 Apr 7.
Seed formation is essential for plant propagation and food production. We present a novel mechanism for the regulation of seed size by a newly identified "gate" at the chalazal end of the ovule regulating nutrient transport into the developing seed. This gate is blocked by callose deposition in unfertilized mature ovules (closed state), but the callose is removed after central cell fertilization, allowing nutrient transport into the seed (open state). However, if fertilization fails, callose deposition persists, preventing transportation of nutrients from the funiculus. A mutant in an ovule-expressed β-1,3-glucanase gene (AtBG_ppap) showed incomplete callose degradation after fertilization and produced smaller seeds, apparently due to its partially closed state. By contrast, an AtBG_ppap overexpression line produced larger seeds due to continuous callose degradation, fully opening the gate for nutrient transport into the seed. The mechanism was also identified in rice, indicating that it potentially could be applied widely to angiosperms to increase seed size.
种子形成对于植物繁殖和粮食生产至关重要。我们提出了一种新的机制，即通过胚珠合点端新发现的“门”来调节种子大小，该“门”调控营养物质向发育中的种子的运输。在未受精的成熟胚珠中，胼胝质沉积会阻断这个“门”（关闭状态），但中央细胞受精后胼胝质会被去除，从而使营养物质能够运输到种子中（开放状态）。然而，如果受精失败，胼胝质沉积会持续存在，阻止营养物质从珠柄运输。一个胚珠表达的β-1,3-葡聚糖酶基因（AtBG_ppap）的突变体在受精后显示出胼胝质降解不完全，产生的种子较小，这显然是由于其处于部分关闭状态。相比之下，AtBG_ppap过表达系由于持续的胼胝质降解，产生了更大的种子，完全打开了营养物质运输到种子的“门”。在水稻中也发现了这种机制，表明它有可能广泛应用于被子植物以增加种子大小。
