The functional role of expansin-like A and B family members remains unclear in plants. In this study, we investigate the functional role of Brassica rapa expansin-like B1 (BrEXLB1) by overexpressing BrEXLB1 sense, antisense and BrEXLB1 specific promoter: GUS in Arabidopsis. The overexpressors of sense BrEXLB1, antisense BrEXLB1 showed variable and unstable pleiotropic effects on leaf growth. Interestingly, overexpressors of sense BrEXLB1 enhances plant height than antisense overexpressors and wild types. GUS reporter-aided analysis of BrEXLB1 promoter showed their activity prominently in seeds, roots and carpels. This is further confirmed by relative quantification of BrEXLB1 among various tissue samples of B. rapa by semi-quantitative Reverse transcription-polymerase chain reaction assay (RT-PCR). We found that BrEXLB1 promoter has several cis-acting elements including light-responsive, phytohormone-responsive, environmental/stress-responsive and tissue-specific elements in promoter sequences. Hence, we analysed the promoter activity of BrEXLB1 by GUS reporter-aided approach, in which stress, phytohormones and other factors regulated changes in GUS transcripts were measured using quantitative RT-PCR. This study suggests that promoter activity is inducible to exogenous application of phytohormones such as indole-3-acetic acid, jasmonic acid, and other factors such as white light and drought stress. These results suggest that BrEXLB1 under its specific promoters may participate in regulation of leaf, plant growth and responds to hormone availability, light quality, dark periods, developmental stages, and drought conditions.

中文翻译：

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甘蓝型油菜扩张蛋白样B1基因（BrEXLB1）调节转基因拟南芥的生长和发育，并引发对非生物胁迫的响应

在植物中，类似expansin的A和B家族成员的功能作用尚不清楚。在这项研究中，我们通过在拟南芥中过表达BrEXLB1有义，反义和BrEXLB1特异性启动子：GUS来研究甘蓝型油菜扩张蛋白样B1（BrEXLB1）的功能。有义BrEXLB1，反义BrEXLB1的过表达对叶片生长表现出可变和不稳定的多效作用。有趣的是，有义BrEXLB1的过表达比反义过表达和野生型提高了植物高度。GUS记者对BrEXLB1的分析启动子在种子，根和心皮中表现出显着的活性。通过半定量逆转录-聚合酶链反应分析（RT-PCR）对B. rapa的各种组织样品之间的BrEXLB1进行相对定量，进一步证实了这一点。我们发现BrEXLB1启动子在启动子序列中具有几个顺式作用元件，包括光响应性，植物激素响应性，环境/应激响应性和组织特异性元素。因此，我们分析了BrEXLB1的启动子活性通过GUS记者辅助方法，其中压力，植物激素和其他因素调节了GUS转录物的变化，使用定量RT-PCR进行了测量。这项研究表明启动子活性可诱导外源应用植物激素，例如吲哚-3-乙酸，茉莉酸和其他因素，例如白光和干旱胁迫。这些结果表明，BrEXLB1在其特定的启动子下可能参与叶片，植物生长的调节，并对激素的利用，光照质量，黑暗时期，发育阶段和干旱条件产生反应。