Leaf veins play an important role in plant growth and development, and the bundle sheath (BS) is believed to greatly improve the photosynthetic efficiency of C4 plants. The OBV mutation in tomato (Solanum lycopersicum) results in dark veins and has been used widely in processing tomato varieties. However, physiological performance has difficulty explaining fitness in production. In this study, we confirmed that this mutation was caused by both the increased chlorophyll content and the absence of bundle sheath extension (BSE) in the veins. Using genome-wide association analysis and map-based cloning, we revealed that OBV encoded a C2H2L domain class transcription factor. It was localized in the nucleus and presented cell type-specific gene expression in the leaf veins. Furthermore, we verified the gene function by generating CRISPR/Cas9 knockout and overexpression mutants of the tomato gene. RNA sequencing analysis revealed that OBV was involved in regulating chloroplast development and photosynthesis, which greatly supported the change in chlorophyll content by mutation. Taken together, these findings demonstrated that OBV affected the growth and development of tomato by regulating chloroplast development in leaf veins. This study also provides a solid foundation to further decipher the mechanism of BSEs and to understand the evolution of photosynthesis in land plants.

中文翻译：

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OBV（模糊静脉）是一种 C2H2 锌指转录因子，正向调节番茄（Solanum lycopersicum）叶脉中的叶绿体发育和束鞘延伸形成

叶脉在植物生长发育中起重要作用，束鞘（BS）被认为能大大提高C的光合效率。4植物。这OBV番茄突变（番茄) 导致深色纹理，并已广泛用于加工番茄品种。然而，生理表现难以解释生产中的适应性。在这项研究中，我们证实这种突变是由叶绿素含量增加和静脉中缺乏束鞘延伸 (BSE) 引起的。使用全基因组关联分析和基于图谱的克隆，我们发现OBV编码一个 C2H2L 域类转录因子。它位于细胞核中，并在叶脉中呈现细胞类型特异性基因表达。此外，我们通过生成番茄基因的 CRISPR/Cas9 敲除和过表达突变体来验证基因功能。RNA测序分析显示，OBV参与调节叶绿体发育和光合作用，这极大地支持了通过突变改变叶绿素含量。综上所述，这些发现表明OBV通过调节叶脉叶绿体发育影响番茄的生长发育。该研究还为进一步破译疯牛病的发病机制和了解陆地植物光合作用的演化提供了坚实的基础。