State Key Laboratory of Crop Stress Biology in Arid Areas and College of Agronomy, Northwest A&F University, Yangling, Shaanxi 712100, China.
State Key Laboratory of Crop Stress Biology in Arid Areas and College of Agronomy, Northwest A&F University, Yangling, Shaanxi 712100, China.
Plant Sci. 2022 Jul;320:111274. doi: 10.1016/j.plantsci.2022.111274. Epub 2022 Apr 4.
TaGW2 has been identified as a key determinant of the grain weight in wheat (Triticum aestivum L.). In our previous study, we found that the grain size differs in Chinese Spring (CS) and its TaGW2-6A allelic variant (NIL31). In addition, the expression of the key starch biosynthesis enzyme gene TaAGPS differs significantly in the two materials. However, the underlying molecular mechanism associated with the action of TaGW2-6A has not been reported. In the present study, we found that TaGW2-6A-CS interacted with TaAGPS, whereas TaGW2-6A-NIL31 did not interact with it in vitro and in vivo. Furthermore, we found that the C-terminal LXLX domain (376-424 aa) of TaGW2-6A recognized TaAGPS. However, the TaGW2-6A allelic variant lacked this key interaction region due to premature translation termination. We also found that TaGW2-6A-CS can ubiquitinate TaAGPS and degrade it via the 26 S proteasome pathway. In addition, our analysis of the activity of ADP-glucose pyrophosphorylase (AGPase) indicated that the AGPase level in the endosperm cells was lower in CS than NIL31. Cytological observations demonstrated that the average number of starch granules and the average area of starch granules in endosperm cells were lower in CS than NIL31. The overexpression of TaAGPS positively regulated the seed size in transgenic Arabidopsis. Our findings provide novel insights into the molecular mechanism that allows TaGW2-6A-TaAGPS to regulate seed size via the starch synthesis pathway.
TaGW2 被鉴定为小麦（Triticum aestivum L.）粒重的关键决定因素。在我们之前的研究中，我们发现中国春（CS）及其 TaGW2-6A 等位变异体（NIL31）的粒型不同。此外，这两种材料中关键淀粉生物合成酶基因 TaAGPS 的表达差异显著。然而，与 TaGW2-6A 作用相关的潜在分子机制尚未报道。在本研究中，我们发现 TaGW2-6A-CS 与 TaAGPS 相互作用，而 TaGW2-6A-NIL31 则不能在体外和体内相互作用。此外，我们发现 TaGW2-6A 的 C 端 LXLX 结构域（376-424 aa）识别 TaAGPS。然而，由于翻译提前终止，TaGW2-6A 等位变异体缺乏这个关键的相互作用区域。我们还发现 TaGW2-6A-CS 可以泛素化 TaAGPS，并通过 26S 蛋白酶体途径降解它。此外，我们对 ADP-葡萄糖焦磷酸化酶（AGPase）活性的分析表明，CS 中胚乳细胞中的 AGPase 水平低于 NIL31。细胞学观察表明，CS 中胚乳细胞的淀粉粒平均数量和淀粉粒平均面积均低于 NIL31。TaAGPS 的过表达正向调节转基因拟南芥的种子大小。我们的研究结果为 TaGW2-6A-TaAGPS 通过淀粉合成途径调节种子大小的分子机制提供了新的见解。
