Dwarfing is the development trend of pepper breeding. It is of great practical and scientific value to generate new dwarf germplasms, and identify new genes or alleles conferring dwarf traits in pepper. In our previous study, a weakly BR-insensitive dwarf mutant, E29, was obtained by EMS mutagenesis of the pepper inbred line 6421. It can be used as a good parent material for breeding new dwarf varieties. Here, we found that this dwarf phenotype was controlled by a single recessive gene. Whole-genome resequencing, dCAPs analysis, and VIGs validation revealed that this mutation was caused by a nonsynonymous single-nucleotide mutation (C to T) in CaBRI1. An enzyme activity assay, transcriptome sequencing, and BL content determination further revealed that an amino-acid change (Pro1157Ser) in the serine/threonine protein kinase and catalytic (S_TKc) domain of CaBRI1 impaired its kinase activity and caused the transcript levels of two important genes (CaDWF4 and CaROT3) participating in BR biosynthesis to increase dramatically in the E29 mutant, accompanied by significantly increased accumulation of brassinolide (BL). Therefore, we concluded that the novel single-base mutation in CaBRI1 conferred the dwarf phenotype and resulted in brassinosteroid (BR) accumulation in pepper. This study provides a new allelic variant of the height-regulating gene CaBRI1 that has theoretical and practical values for the breeding of the plants suitable for the facility cultivation and mechanized harvesting of pepper varieties.

中文翻译：

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CaBRI1的新型单碱基突变赋予辣椒矮化表型和油菜素类固醇积累。

矮化是辣椒育种的发展趋势。产生新的矮化种质，鉴定赋予辣椒矮化性状的新基因或等位基因，具有重要的实践和科学价值。在我们先前的研究中，通过胡椒自交系6421的EMS诱变获得了对BR不敏感的矮化突变体E29。该突变体可以作为育种新矮化品种的良好母体材料。在这里，我们发现该矮表型受单个隐性基因控制。全基因组重测序，dCAP分析和VIG验证表明，此突变是由CaBRI1中的非同义单核苷酸突变（C到T）引起的。酶活性测定，转录组测序，和BL含量测定进一步揭示，CaBRI1的丝氨酸/苏氨酸蛋白激酶和催化（S_TKc）域中的氨基酸变化（Pro1157Ser）削弱了其激酶活性，并导致参与其中的两个重要基因（CaDWF4和CaROT3）的转录水平BR生物合成在E29突变体中显着增加，同时伴随着油菜素内酯（BL）的积累显着增加。因此，我们得出的结论是，CaBRI1中的新型单碱基突变赋予了矮表型，并导致胡椒中的油菜素类固醇（BR）积累。这项研究提供了一种新的高度调节基因CaBRI1的等位基因变体，该变体对适于植物栽培和机械化收获辣椒品种的植物的育种具有理论和实践价值。