背景回顾：Cold stress seriously affects plant development, resulting in heavy agricultural losses. L-ascorbic acid (AsA, vitamin C) is an antioxidant implicated in abiotic stress tolerance and metabolism of reactive oxygen species (ROS). Understanding whether and how cold stress elicits AsA biosynthesis to reduce oxidative damage is important for developing cold-resistant plants. 

结果1-低温诱导AsA积累：Here, we show that the accumulation of AsA in response to cold stress is a common mechanism conserved across the plant kingdom, from single-cell algae to angiosperms. 

结果2-低温-PosF21-AsA-低温抗性：We identified a basic leucine zipper domain (bZIP) transcription factor (TF) of kiwifruit (Actinidia eriantha Benth.), AcePosF21, which was triggered by cold and is involved in the regulation of kiwifruit AsA biosynthesis and defense responses against cold stress. 

结果3-PosF21-MYB102-GGP3-AsA-低温抗性：AcePosF21 interacted with the R2R3-MYB TF AceMYB102 and directly bound to the promoter of the gene encoding GDP-L-galactose phosphorylase 3 (AceGGP3), a key conduit for regulating AsA biosynthesis, to upregulate AceGGP3 expression and produce more AsA, which neutralized the excess ROS induced by cold stress. On the contrary, VIGS or CRISPR-Cas9-mediated editing of AcePosF21 decreased AsA content and increased the generation of ROS in kiwifruit under cold stress. 

结论：Taken together, we illustrated a model for the regulatory mechanism of AcePosF21-mediated regulation of AceGGP3 expression and AsA biosynthesis to reduce oxidative damage by cold stress, which provides valuable clues for manipulating the cold resistance of kiwifruit.

低温胁迫严重影响植物的发育，导致农业减产。L-抗坏血酸（AsA），又称维生素C，是一个抗氧化剂，参与非生物胁迫耐受性和活性氧物质（ROS）的代谢。理解低温胁迫是否以及如何诱导AsA的生物合成，从而减少氧化应激损伤，对于开发低温抗性植物十分重要。本文中，作者发现植物响应低温积累AsA是一个普遍的机制，从单细胞藻类到被子植物中都存在。作者在猕猴桃中鉴定到了一个bZIP转录因子AcePosF21，其被低温所诱导，参与猕猴桃中的AsA生物合成和对低温的防御响应。AcePosF21与R2R3-MYB转录因子AceMYB102互作，直接结合到猕猴桃AsA生物合成关键调控基因AceGGP3的启动子上，上调后者的表达并促进AsA的生成，从而能够中和由低温诱导产生的过量ROS。相反，VIGS或者CRISPR-Cas9介导的AcePosF21编辑降低了猕猴桃在低温胁迫下的AsA含量并增加了ROS的产生。综上，作者揭示了一个由AcePosF21介导的AceGGP3基因表达，从而通过增加AsA的含量，减少低温胁迫下的氧化损伤，这为猕猴桃的低温抗性育种提供了珍贵线索和基因资源。

** 李大卫 **