State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangdong Laboratory for Lingnan Modern Agriculture College of Life Sciences, South China Agricultural University, Guangzhou 510642, China.
Institute of Fruit Tree Research, Guangdong Academy of Agricultural Sciences, Key Laboratory of South Subtropical Fruit Biology and Genetic Resource Utilization, Ministry of Agriculture and Rural Affairs, Guangdong Provincial Key Laboratory of Tropical and Subtropical Fruit Tree Research, Guangzhou 510640, China.
Plant Cell. 2023 Sep 1;35(9):3522-3543. doi: 10.1093/plcell/koad181.
Uridine diphosphate (UDP)-sugars are important metabolites involved in the biosynthesis of polysaccharides and may be important signaling molecules. UDP-glucose 4-epimerase (UGE) catalyzes the interconversion between UDP-Glc and UDP-Gal, whose biological function in rice (Oryza sativa) fertility is poorly understood. Here, we identify and characterize the botryoid pollen 1 (bp1) mutant and show that BP1 encodes a UGE that regulates UDP-sugar homeostasis, thereby controlling the development of rice anthers. The loss of BP1 function led to massive accumulation of UDP-Glc and imbalance of other UDP-sugars. We determined that the higher levels of UDP-Glc and its derivatives in bp1 may induce the expression of NADPH oxidase genes, resulting in a premature accumulation of reactive oxygen species (ROS), thereby advancing programmed cell death (PCD) of anther walls but delaying the end of tapetal degradation. The accumulation of UDP-Glc as metabolites resulted in an abnormal degradation of callose, producing an adhesive microspore. Furthermore, the UDP-sugar metabolism pathway is not only involved in the formation of intine but also in the formation of the initial framework for extine. Our results reveal how UDP-sugars regulate anther development and provide new clues for cellular ROS accumulation and PCD triggered by UDP-Glc as a signaling molecule.
尿苷二磷酸（UDP）-糖是参与多糖生物合成的重要代谢物，可能是重要的信号分子。UDP-葡萄糖 4-差向异构酶（UGE）催化 UDP-Glc 和 UDP-Gal 之间的相互转化，其在水稻（Oryza sativa）育性中的生物学功能尚不清楚。在这里，我们鉴定并表征了拟南芥花粉 1（bp1）突变体，并表明 BP1 编码 UGE，它调节 UDP-糖稳态，从而控制水稻花药的发育。BP1 功能的丧失导致 UDP-Glc 的大量积累和其他 UDP-糖的失衡。我们确定 bp1 中较高水平的 UDP-Glc 及其衍生物可能诱导 NADPH 氧化酶基因的表达，导致活性氧（ROS）的过早积累，从而提前进行花药壁的程序性细胞死亡（PCD），但延迟绒毡层降解的结束。作为代谢物的 UDP-Glc 的积累导致胼胝质的异常降解，产生粘性小孢子。此外，UDP-糖代谢途径不仅参与内纹层的形成，也参与外壁初始框架的形成。我们的研究结果揭示了 UDP-糖如何调节花药发育，并为 UDP-Glc 作为信号分子引发细胞内 ROS 积累和 PCD 提供了新的线索。
