Drought stress can severely affect plant growth and crop yield. The cloning and identification of drought-inducible promoters would be of value for genetically-based strategies to improve resistance of crops to drought. Previous studies showed that the MaPIP1;1 gene encoding an aquaporin is involved in the plant drought stress response. In this study, the promoter pMaPIP1;1, which lies 1362 bp upstream of the MaPIP1;1 transcriptional initiation site, was isolated from the banana genome..And the transcription start site(A) is 47 bp before the ATG. To functionally validate the promoter, various lengths of pMaPIP1;1 were deleted and fused to GUS to generate pMaPIP1;1::GUS fusion constructs that were then transformed into Arabidopsis to generate four transformants termed M-P1, M-P2, M-P3 and M-P4.Mannitol treatment was used to simulate drought conditions. All four transformants reacted well to mannitol treatment. M-P2 (− 1274 bp to − 1) showed the highest transcriptional activity among all transgenic Arabidopsis tissues, indicating that M-P2 was the core region of pMaPIP1;1. This region of the promoter also confers high levels of gene expression in response to mannitol treatment. Using M-P2 as a yeast one-hybrid bait, 23 different transcription factors or genes that interacted with MaPIP1;1 were screened. In an dual luciferase assay for complementarity verification, the transcription factor MADS3 positively regulated MaPIP1;1 transcription when combined with the banana promoter. qRT-PCR showed that MADS3 expression was similar in banana leaves and roots under drought stress. In banana plants grown in 45% soil moisture to mimic drought stress, MaPIP1;1 expression was maximized, which further demonstrated that the MADS3 transcription factor can synergize with MaPIP1;1. Together our results revealed that MaPIP1;1 mediates molecular mechanisms associated with drought responses in banana, and will expand our understanding of how AQP gene expression is regulated. The findings lay a foundation for genetic improvement of banana drought resistance.

中文翻译：

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鉴定与 MaPIP1;1 的 1274 bp 启动子相互作用的转录因子，该启动子赋予转基因拟南芥高水平的基因表达和干旱胁迫诱导能力。


干旱胁迫会严重影响植物生长和作物产量。干旱诱导启动子的克隆和鉴定对于提高作物抗旱性的遗传策略具有重要价值。先前的研究表明编码水通道蛋白的MaPIP1;1基因参与植物干旱胁迫反应。本研究从香蕉基因组中分离得到启动子pMaPIP1;1，位于MaPIP1;1转录起始位点上游1362 bp处。转录起始位点(A)位于ATG前47 bp处。为了对启动子进行功能验证，删除了不同长度的 pMaPIP1;1 并与 GUS 融合以生成 pMaPIP1;1::GUS 融合构建体，然后将其转化到拟南芥中以生成称为 M-P1、M-P2、M-P3 的四个转化子和M-P4。甘露醇处理用于模拟干旱条件。所有四个转化体对甘露醇处理反应良好。 M-P2（− 1274 bp 至− 1）在所有转基因拟南芥组织中表现出最高的转录活性，表明M-P2 是pMaPIP1;1 的核心区域。启动子的该区域还响应甘露醇处理而赋予高水平的基因表达。使用M-P2作为酵母单杂交诱饵，筛选了23种与MaPIP1;1相互作用的不同转录因子或基因。在用于互补性验证的双荧光素酶测定中，转录因子 MADS3 与香蕉启动子结合时正向调节 MaPIP1;1 转录。 qRT-PCR 显示干旱胁迫下香蕉叶和根中 MADS3 的表达相似。在模拟干旱胁迫的 45% 土壤湿度下生长的香蕉植株中，MaPIP1;1 表达最大化，这进一步证明 MADS3 转录因子可以与 MaPIP1;1 协同作用。 我们的结果共同揭示了 MaPIP1;1 介导与香蕉干旱反应相关的分子机制，并将扩大我们对 AQP 基因表达如何调节的理解。该研究结果为香蕉抗旱性遗传改良奠定了基础。