Overexpressing Vitamin C Defective 2 reduces fertility and alters Ca2+ signals in Arabidopsis pollen.
Overexpressing Vitamin C Defective 2 reduces fertility and alters Ca2+ signals in Arabidopsis pollen.
复制标题
过度表达维生素 C 缺陷 2 会降低拟南芥花粉中的生育力并改变 Ca2 信号。
DOI：
10.1093/plphys/kiad031
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发表时间：
2023
期刊：
影响因子：
7.4
通讯作者：
Harper,JeffreyF
中科院分区：
文献类型：
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作者：
Weigand,Chrystle;Brady,Deborah;Davis,JamesA;Speicher,Tori;Bacalso,Jonathan;Jones,Dylan;Miller,Gad;Choi,Won-Gyu;Harper,JeffreyF
减轻植物氧化损伤的一种潜在策略是增加抗氧化剂的丰度，如抗坏血酸盐（即维生素C）。拟南芥（A. thaliana）中，抗坏血酸生物合成中的限速步骤是由维生素C缺陷2（VTC 2）编码的磷酸化酶。为了在花粉中特异性地过量表达VTC 2（VTC 2 OE），使用来自在花粉中表达量高出150倍的基因的启动子来表达编码区，导致花粉粒具有8倍增加的VTC 2 mRNA。VTC 2 OE导致近不育表型，花粉传递效率降低50倍，每个角果的种子数减少5倍。离体试验表明，花粉粒更容易破裂（大于两倍）或产生较短的，形态异常的花粉管。包括一个基因编码的Ca 2+报告，mCherry-GCaMP 6 fast（CGf），揭示了花粉管与改变尖端集中的Ca 2+动态和增加爆裂频率在振荡和逮捕的增长期间。尽管有这些表型，VTC 2 OE花粉未能显示预期的抗坏血酸增加或活性氧减少，如使用氧化还原敏感染料或roGFP 2所测量的。然而，mRNA表达分析显示，编码两种酶的mRNA减少了两倍以上，这两种酶对与细胞壁或脂质和蛋白质的糖修饰相关的生物合成途径至关重要：GDP-d-甘露糖焦磷酸化酶（GMP）和GDP-d-甘露糖3′，5 ′差向异构酶（GME）。这些结果支持了一个模型，在该模型中，花粉中由VTC 2 OE引起的近不育缺陷与反馈机制相关，该机制可以改变对花粉管生长和育性至关重要的一个或多个信号传导或代谢途径。
A potential strategy to mitigate oxidative damage in plants is to increase the abundance of antioxidants, such as ascorbate (i.e. vitamin C). In Arabidopsis (A. thaliana), a rate-limiting step in ascorbate biosynthesis is a phosphorylase encoded byVitamin C Defective 2(VTC2). To specificallyoverexpressVTC2(VTC2OE) in pollen, the coding region was expressed using a promoter from a gene with ∼150-fold higher expression in pollen, leading to pollen grains with an eight-fold increasedVTC2mRNA.VTC2OE resulted in a near-sterile phenotype with a 50-fold decrease in pollen transmission efficiency and a five-fold reduction in the number of seeds per silique. In vitro assays revealed pollen grains were more prone to bursting (greater than two-fold) or produced shorter, morphologically abnormal pollen tubes. The inclusion of a genetically encoded Ca2+reporter, mCherry-GCaMP6fast (CGf), revealed pollen tubes with altered tip-focused Ca2+dynamics and increased bursting frequency during periods of oscillatory and arrested growth. Despite these phenotypes,VTC2OE pollen failed to show expected increases in ascorbate or reductions in reactive oxygen species, as measured using a redox-sensitive dye or a roGFP2. However, mRNA expression analyses revealed greater than two-fold reductions in mRNA encoding two enzymes critical to biosynthetic pathways related to cell walls or glyco-modifications of lipids and proteins: GDP-d-mannose pyrophosphorylase (GMP) and GDP-d-mannose 3′,5′ epimerase (GME). These results support a model in which the near-sterile defects resulting fromVTC2OE in pollen are associated with feedback mechanisms that can alter one or more signaling or metabolic pathways critical to pollen tube growth and fertility.