Horticulture Institute, Sichuan Academy of Agricultural Sciences, Chengdu, 610066, China.
Vegetable Germplasm Innovation and Variety Improvement Key Laboratory of Sichuan Province, Chengdu, 610066, China.
BMC Plant Biol. 2022 Sep 1;22(1):425. doi: 10.1186/s12870-022-03807-2.
Hot pepper (Capsicum annuum L.) is one of the world's oldest domesticated crops. It has poor waterlogging tolerance, and flooding frequently results in plant death and yield reduction. Therefore, understanding the molecular mechanisms associated with pepper waterlogging tolerance is essential to grow new varieties with stronger tolerance.
In this study, we discovered that after 5 days of flooding, the growth rate of waterlogging-tolerant pepper cultivars did not reduce to a large extent. Physiological data revealed that chlorophyll concentration was not significantly affected by flooding; however, stomatal conductance was altered considerably 0-5 days after flooding, and the net photosynthesis rate changed substantially 5-10 days after flooding. In addition, the root activity of waterlogging-tolerant varieties was substantially higher after flooding for 10 days than that of the control. This implies that the effect of flooding is associated with changes in the root environment, which ultimately affects photosynthesis. We evaluated changes in gene expression levels between two pepper types at the same time point and the same pepper variety at different time points after flooding stress treatment and performed a screening for multiple potential genes. These differentially expressed genes (DEGs) were further analyzed for functional enrichment, and the results revealed that antioxidase genes, cell wall synthesis pathway genes, and calcium ion regulation pathway genes might be associated with waterlogging tolerance. Other genes identified in peppers with waterlogging tolerance included those associated with lignin synthesis regulation, reactive oxygen species (ROS) regulation pathways, and others associated with stress resistance. Considerable changes in the expression levels of these genes were recorded 5 days after waterlogging, which was consistent with a considerable increase in oxidase content that was also noted on the fifth day after flooding. The quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) findings revealed that among the 20 selected DEGs, including genes such as mitogen-activated protein kinase 3 (MPK3) and calcium-binding protein 4 (CML4), approximately 80% of the gene expression patterns were consistent with our RNA-seq dataset.
The findings of this study suggest that ROS modulation, increased antioxidase activity, lignin formation, and the expression of stress resistance genes help peppers with waterlogging tolerance resist flooding stress in the early stages. These findings provide a basis for further investigation of the molecular mechanisms responsible for waterlogging tolerance in pepper and may be a critical reference for the breeding of hot pepper.
辣椒（Capsicum annuum L.）是世界上最古老的驯化作物之一。它对水淹胁迫的耐受性差，经常发生洪水导致植物死亡和减产。因此，了解与辣椒耐水淹胁迫相关的分子机制对于培育具有更强耐受性的新品种至关重要。
在这项研究中，我们发现水淹耐受型辣椒品种在 5 天后的生长速度并没有大幅度降低。生理数据显示，叶绿素浓度没有受到水淹的显著影响；然而，水淹后 0-5 天，气孔导度发生了很大的变化，净光合速率在水淹后 5-10 天发生了显著变化。此外，水淹 10 天后，耐水淹品种的根活力明显高于对照。这意味着水淹的影响与根环境的变化有关，最终影响光合作用。我们同时评估了两种辣椒类型在同一时间点和水淹胁迫处理后同一辣椒品种在不同时间点的基因表达水平变化，并对多个潜在基因进行了筛选。这些差异表达基因（DEGs）进一步进行了功能富集分析，结果表明，抗氧化酶基因、细胞壁合成途径基因和钙离子调节途径基因可能与耐水淹胁迫有关。在耐水淹胁迫的辣椒中还发现了与木质素合成调节、活性氧（ROS）调节途径以及其他与抗逆性相关的基因。这些基因的表达水平在水淹后 5 天发生了显著变化，这与第五天观察到的氧化酶含量的显著增加一致。定量逆转录聚合酶链反应（qRT-PCR）的结果表明，在所选择的 20 个差异表达基因中，包括丝裂原活化蛋白激酶 3（MPK3）和钙结合蛋白 4（CML4）等基因，大约 80%的基因表达模式与我们的 RNA-seq 数据集一致。
本研究表明，ROS 调节、抗氧化酶活性增加、木质素形成和抗逆基因的表达有助于辣椒在早期抵抗水淹胁迫。这些发现为进一步研究辣椒耐水淹胁迫的分子机制提供了基础，也可能为辣椒的培育提供重要参考。
