TSWV侵染番茄引起紫脉的叶绿体超微结构病变和质体色素物质代谢的关系

Study of the relationship between TSWV infection-induced chloroplast ultrastructural lesion and plastid pigment substance metabolism in the purple veins of tomato leaves

关键词:  TSWV，番茄，紫脉叶片，叶绿体，色素，类胡萝卜素，质体小球

Key words:  TSWV, tomato, purple veined leaves, chloroplast, pigment, carotenoid, plastoglobule

摘要:

病毒侵染植物后引起叶、花和果实色素代谢异常，如番茄斑萎病毒（tomato spotted wilt orthotospovirus，TSWV）侵染番茄后引起紫脉症状，但病毒对寄主植物色素代谢干扰的影响机制尚未明确。本研究以感染TSWV的番茄（Solanum lycopersicum）品种‘草莓番茄’不同发病程度紫脉叶片样品为实验材料，分析紫脉叶片中叶绿体超微结构病变、质体色素物质含量及其相关性。结果表明：（1）TSWV侵染的番茄叶片中叶绿体结构畸变程度随紫脉症状的加深而逐渐加重，质体小球的数量及体积增加，基粒的数量降低，叶绿素a、b及总叶绿素含量降低。（2）总叶绿素含量与质体小球数量呈负相关，与基粒数量呈正相关。（3）紫脉叶片中类胡萝卜素合成途径相关酶基因（ZEP，PDS，LCYE等）及色素转录调控因子AP2a、MYB12和PIF1a的表达水平显著降低。（4）TSWV侵染番茄后其N基因复制表达引起番茄叶片叶绿体超微结构病变和色素合成代谢变化，进而引起叶片出现紫脉症状。上述结果为进一步探索TSWV侵染寄主植物后颜色症状形成的机制提供新的途径。本研究首次报道了TSWV侵染番茄引起紫脉叶片的叶绿体超微结构病变和色素物质之间的关系，色素代谢调控因子可能是TSWV致病的新靶点，并为通过靶点基因编辑抗TSWV番茄种质创制提供新的方向。

Abstract:

The virus infects plants and causes abnormal metabolism of pigments in leaves, flowers and fruits. Tomato spotted wilt orthotospovirus (TSWV) infection can cause purple veins in tomato leaves, but the mechanism of action is unclear. The purple-veined leaves of ‘strawberry tomato’ plants infected with TSWV of different disease severities were used as experimental materials. We analyzed lesions of chloroplast ultrastructure, and plastid pigment substance content and evaluated the correlation of these parameters on purple-veined tomato leaves. The results were as follows: (1) The degree of deformity of the chloroplast structure in TSWV-infected tomato purple-veined leaves were increased gradually, the number and volume of plastoglobule were increased, the number of starch granules was decreased, and the contents of chlorophyll a and b, and total chlorophyll were also decreased. (2) The total chlorophyll content was negatively correlated with the number of plastoglobule and positively correlated with the number of grana. (3) The expression levels of genes encoding enzymes related to the carotenoid synthesis pathway (ZEP, PDS, and LCYE) and the pigment transcription regulatory factors AP2a, MYB12 and PIF1a were significantly decreased. (4) The expression of TSWV N gene caused changes in the chloroplast ultrastructure and pigment anabolism in TSWV-infected tomato leaves. Above results provide a foundation for further research on the mechanism of symptom formation after TSWV infects host plants. This study was the first to reveal the relationship between chloroplast ultrastructural changes and pigment substances in tomato purple vein leaves caused by TSWV infection, regulatory factors involved in pigment metabolism may be new targets of TSWV pathogenesis, providing a new direction for the development of TSWV-resistant tomato cultivation through targeted gene editing.