Comparative Genomic and Transcriptomic Analysis of Aquaporin Gene Family Members in Dalbergia Species

Aquaporins (AQPs) are channel proteins that play a pivotal role in transport of water and other small neutral solutes. However, molecular aspects of AQPs in Dalbergia species remain scarce. A comparative genomic and transcriptomic investigation of the AQP gene family identified a total of 147 genes encoding AQPs in seven species of Dalbergia and these were classified into five subfamilies: 50 plasma membrane intrinsic proteins (PIPs), 44 nodulin-like intrinsic proteins (NIPs), 44 tonoplast intrinsic proteins (TIPs), 4 small basic intrinsic proteins (SIPs) and 5 X-intrinsic proteins (XIPs). Among the AQPs, analysis of conserved motifs suggested that aquaporins exhibit a high degree of genetic conservation. Protein–protein interactions have revealed that PIPs might interact with Glycerol-3-phosphate dehydrogenase protein to facilitate the transport of water and small neutral solutes across cell membranes. GO annotation suggested AQPs’ involvement in transmembrane transporter activity in response to abiotic stress signals in response to fluoride, salt, or inorganic substances. Furthermore, miR5251 and miR5234 were identified as frequently targeting AQPs to control the post-transcriptional expression of these genes. 3D structures, and post-translational modifications deduced the regulation of gene expression of aquaporins. Transcriptomic data suggested differential expression of AQPs under wounding stress in D. odorifera. The expression patterns of DsiAQP-05 and DsiAQP-09 exhibited variations in dieback resistant and susceptible D. sissoo plants during drought stress conditions in the RT-PCR analysis. These findings are significant for understanding the molecular functions of AQPs and basis for genetic improvement of Dalbergia plant species against abiotic stress tolerance in future.

水通道蛋白（Aquaporins，AQPs）是一类通道蛋白，在水及其他小型中性溶质的跨膜转运过程中发挥关键作用。然而，目前关于黄檀属（Dalbergia）植物中水通道蛋白的分子层面研究仍较为匮乏。本研究对黄檀属7个物种的AQP基因家族开展比较基因组学与转录组学分析，共鉴定得到147个编码水通道蛋白的基因，可划分为5个亚家族：50个质膜内在蛋白（plasma membrane intrinsic proteins，PIPs）、44个结瘤素样内在蛋白（nodulin-like intrinsic proteins，NIPs）、44个液泡膜内在蛋白（tonoplast intrinsic proteins，TIPs）、4个小碱性内在蛋白（small basic intrinsic proteins，SIPs）以及5个X内在蛋白（X-intrinsic proteins，XIPs）。对水通道蛋白保守基序的分析显示，该类蛋白具有高度的遗传保守性。蛋白质相互作用分析表明，质膜内在蛋白可能与甘油-3-磷酸脱氢酶（Glycerol-3-phosphate dehydrogenase）相互作用，以促进水及小型中性溶质跨细胞膜转运。基因本体（Gene Ontology，GO）注释结果显示，水通道蛋白参与跨膜转运活性，以响应氟化物、盐胁迫或无机物质引发的非生物胁迫信号。此外，研究鉴定出miR5251与miR5234可靶向调控水通道蛋白基因，进而控制其转录后表达。基于三维结构与翻译后修饰特征，可推知水通道蛋白的基因表达调控机制。转录组数据显示，降香黄檀（Dalbergia odorifera，D. odorifera）在创伤胁迫下，其水通道蛋白基因呈现差异表达模式。RT-PCR分析结果表明，在干旱胁迫条件下，枯梢病抗病与感病印度黄檀（Dalbergia sissoo，D. sissoo）植株中，DsiAQP-05与DsiAQP-09的表达模式存在显著差异。本研究结果有助于深入解析水通道蛋白的分子功能，同时为未来通过遗传改良提升黄檀属植物的非生物胁迫耐受性提供理论依据。