State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
Planta. 2024 Sep 20;260(4):102. doi: 10.1007/s00425-024-04513-z.
The leaf color asymmetry found in the reciprocal hybrids C. hystrix × C. sativus (HC) and C. sativus × C. hystrix (CH) could be influenced by the CsPPR gene (CsaV3_1G038250.1). Most angiosperm organelles are maternally inherited; thus, the reciprocal hybrids usually exhibit asymmetric phenotypes that are associated with the maternal parent. However, there are two sets of organelle genomes in the plant cytoplasm, and the mechanism of reciprocal differences are more complex and largely unknown, because the chloroplast genes are involved besides mitochondrial genes. Cucumis spp. contains the species, i.e., cucumber and melon, which chloroplasts and mitochondria are maternally inherited and paternally inherited, respectively, serving as good materials for the study of reciprocal differences. In this study, leaf color asymmetry was observed in the reciprocal hybrids (HC and CH) derived from C. sativus (2n = 14, CC) and C. hystrix (2n = 24, HH), where the leaves of HC were found to have reduced chlorophyll content, abnormal chloroplast structure and lower photosynthetic capacity. Transcriptomic analysis revealed that the chloroplast development-related genes were differentially expressed in leaf color asymmetry. Genetic analysis showed that leaf color asymmetry was caused by the maternal chloroplast genome. Comparative analysis of chloroplast genomes revealed that there was no mutation in the chloroplast genome during interspecific hybridization. Moreover, a PPR gene (CsaV3_1G038250.1) with RNA-editing function was found to be involved in the regulation of leaf color asymmetry. These findings provide new insights into the regulatory mechanisms of asymmetric phenotypes in plant reciprocal crosses.
在正反交杂种 C. hystrix × C. sativus (HC) 和 C. sativus × C. hystrix (CH) 中发现的叶片颜色不对称性可能受 CsPPR 基因（CsaV3_1G038250.1）影响。大多数被子植物细胞器是母系遗传的；因此，正反交杂种通常表现出与母本相关的不对称表型。然而，植物细胞质中存在两套细胞器基因组，而且由于涉及到线粒体基因，正反交差异的机制更加复杂且很大程度上尚不清楚。黄瓜属植物包含黄瓜和甜瓜等物种，其叶绿体和线粒体分别为母系遗传和父系遗传，是研究正反交差异的良好材料。在本研究中，观察到源自 C. sativus（2n=14，CC）和 C. hystrix（2n=24，HH）的正反交杂种（HC 和 CH）的叶片颜色不对称性，其中 HC 的叶片叶绿素含量降低、叶绿体结构异常且光合作用能力较低。转录组分析显示，叶片颜色不对称性与叶绿体发育相关基因的差异表达有关。遗传分析表明，叶片颜色不对称性是由母系叶绿体基因组引起的。叶绿体基因组比较分析显示，种间杂交过程中叶绿体基因组没有发生突变。此外，发现一个具有 RNA 编辑功能的 PPR 基因（CsaV3_1G038250.1）参与调控叶片颜色不对称性。这些发现为植物正反交杂种不对称表型的调控机制提供了新的见解。
