Citrus Research Institute of Southwest University, National Citrus Engineering Technology Research Center, Chongqing, 400712, China.
J Plant Res. 2023 May;136(3):371-382. doi: 10.1007/s10265-023-01447-7. Epub 2023 Mar 2.
Ascorbate peroxidase (APX) is one of the most important antioxidant enzymes in the reactive oxygen metabolic pathway of plants. The role of APX under biotic and abiotic stress conditions has been explored, but the response pattern of APX under biotic stresses is relatively less known. In this study, seven CsAPXs gene family members were identified based on the sweet orange (Citrus sinensis) genome and subjected to evolutionary and structural analysis using bioinformatics software. The APX genes of lemon (ClAPXs) were cloned and showed a high conservation to CsAPXs by sequences alignment. In citrus yellow vein clearing virus (CYVCV)-infected Eureka lemons (C. limon) at 30th day post inoculation, APX activity and accumulation of hydrogen peroxide (HO) and malondialdehyde were measured to be 3.63, 2.29, and 1.73 times to that of the healthy control. The expression levels of 7 ClAPX genes in different periods of CYVCV-infected Eureka lemon were analyzed. Notably, ClAPX1, ClAPX5, and ClAPX7 showed higher expression levels compared to healthy plants, while ClAPX2, ClAPX3, and ClAPX4 showed lower expression levels. Functional identification of ClAPX1 in Nicotiana benthamiana showed that increasing the expression of ClAPX1 could significantly reduce the accumulation of HO, and it was verified that ClAPX1 is located in the plasma membrane of the cell. The present study provided information on the evolution and function of citrus APXs and revealed for the first time their response pattern to CYVCV infection.
抗坏血酸过氧化物酶 (APX) 是植物活性氧代谢途径中最重要的抗氧化酶之一。APX 在生物和非生物胁迫条件下的作用已经被探索，但对生物胁迫下 APX 的响应模式了解较少。本研究基于甜橙（Citrus sinensis）基因组鉴定了 7 个 CsAPXs 基因家族成员，并使用生物信息学软件对其进行了进化和结构分析。克隆了柠檬（ClAPXs）的 APX 基因，通过序列比对发现其与 CsAPXs 高度保守。在感染柑橘黄龙病（CYVCV）的尤里卡柠檬（C. limon）中，在接种后第 30 天测量 APX 活性和过氧化氢（HO）和丙二醛的积累，发现其分别是健康对照的 3.63、2.29 和 1.73 倍。分析了不同时期感染 CYVCV 的尤里卡柠檬中 7 个 ClAPX 基因的表达水平。值得注意的是，ClAPX1、ClAPX5 和 ClAPX7 的表达水平与健康植物相比更高，而 ClAPX2、ClAPX3 和 ClAPX4 的表达水平则更低。在本氏烟中鉴定 ClAPX1 的功能表明，增加 ClAPX1 的表达可以显著减少 HO 的积累，并且验证了 ClAPX1 位于细胞的质膜上。本研究提供了柑橘 APXs 的进化和功能信息，并首次揭示了它们对 CYVCV 感染的响应模式。
