背景回顾：The major antioxidant L-ascorbic acid (AsA) plays important roles in plant growth, development and stress responses.  

提出问题：However, the importance of AsA concentration and the regulation of AsA metabolism in plant reproduction remains unclear. In Arabidopsis (Arabidopsis thaliana) anthers, the tapetum monolayer undergoes cell differentiation to support pollen development.

主要发现：Here, we report that a transcription factor, DEFECTIVE IN TAPETAL DEVELOPMENT AND FUNCTION 1 (TDF1), inhibits tapetal cell division leading to cell differentiation. 

结果1-TDF1-SKS18-氧化AsA：We identified SKEWED5-SIMILAR 18 (SKS18) as a downstream target of TDF1. Enzymatic assays showed that SKS18, annotated as a multicopper oxidase-like protein, has ascorbate oxidase activity, leading to AsA oxidation.

结果2-TDF1-VTC1-合成AsA：We also show that VITAMIN C DEFECTIVE1 (VTC1), an AsA biosynthetic enzyme, is negatively controlled by TDF1 to maintain proper AsA contents.

结果3-TDF1-SKS18/VTC1-绒毡层细胞：Consistently, either knockout of SKS18 or VTC1 overexpression raised AsA concentrations, resulting in extra tapetal cells, while SKS18 overexpression in tdf1 or the vtc1-3 tdf1 double mutant mitigated their defective tapetum.

结果4-AsA-ROS-绒毡层细胞：We observed that high AsA concentrations caused lower accumulation of reactive oxygen species (ROS) in tapetal cells. Overexpression of ROS scavenging genes in tapetum restored excess cell divisions. 

结论：Thus, our findings demonstrate that TDF1-regulated AsA balances cell division and cell differentiation in the tapetum through governing ROS homeostasis.

L-抗坏血酸（AsA）作为抗氧化物质，在植物生长、发育和胁迫响应中发挥重要作用。但是，AsA浓度以及AsA代谢调控在植物生殖中的作用还不清清楚。在拟南芥花药中，单细胞层的绒毡层会经历细胞分化以支撑花粉发育。本文中，作者发现转录因子TDF1能够抑制绒毡层细胞分裂，导致细胞分化。作者发现SKS18作为TDF1的下游靶基因发挥作用。SKS18被注释为一个类多铜氧化酶蛋白，酶活试验显示其具有抗坏血酸氧化酶活性，能够氧化AsA。作者还发现AsA生物合酶VTC1受到TDF1的负调控，从而保证适当的AsA浓度。与此一致，无论是SKS18基因的敲除，还是VTC1基因的过表达，会导致AsA浓度的提升，从而形成过多的绒毡层细胞；同时，在tdf1突变体和vtc1-3 tdf1突变体中过表达SKS18基因，能够缓解这些突变体的绒毡层缺陷表型。作者发现过高的AsA浓度会导致绒毡层细胞中活性氧物质（ROS）的积累变少。在绒毡层中过表达ROS清除基因，能够恢复过多细胞分裂的表型。因此，本文的研究结果揭示了一个受TDF1调控的AsA，通过氧化还原内稳态来介导绒毡层细胞分裂与细胞分化之间的平衡。

** 楼 悦 **