• Advanced transcriptome sequencing has revealed that the majority of eukaryotic genes undergo alternative splicing (AS). Nonetheless, little effort has been dedicated to investigating the functional relevance of particular splicing events, even those in the key developmental and hormonal regulators.
• Combining approaches of genetics, biochemistry and advanced confocal microscopy, we describe the impact of alternative splicing on the PIN7 gene in the model plant Arabidopsis thaliana. PIN7 encodes a polarly localized transporter for the phytohormone auxin and produces two evolutionarily conserved transcripts, PIN7a and PIN7b.
• PIN7a and PIN7b, differing in a four amino acid stretch, exhibit almost identical expression patterns and subcellular localization. We reveal that they are closely associated and mutually influence each other's mobility within the plasma membrane. Phenotypic complementation tests indicate that the functional contribution of PIN7b per se is minor, but it markedly reduces the prominent PIN7a activity, which is required for correct seedling apical hook formation and auxin-mediated tropic responses.
• Our results establish alternative splicing of the PIN family as a conserved, functionally relevant mechanism, revealing an additional regulatory level of auxin-mediated plant development.

中文翻译：

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生长素介导的拟南芥热带反应需要 PIN7 剪接异构体的相互相反的活性

• 先进的转录组测序表明，大多数真核基因都经历了选择性剪接 (AS)。尽管如此，很少有人致力于研究特定剪接事件的功能相关性，即使是关键发育和激素调节剂中的那些。
• 结合遗传学、生物化学和先进的共聚焦显微镜的方法，我们描述了可变剪接对模式植物拟南芥PIN7基因的影响。PIN7编码植物激素生长素的极性定位转运蛋白，并产生两个进化上保守的转录本，即 PIN7a和PIN7b。
• PIN7a 和 PIN7b 在四个氨基酸序列中不同，表现出几乎相同的表达模式和亚细胞定位。我们揭示了它们密切相关并相互影响彼此在质膜内的流动性。表型互补测试表明 PIN7b本身的功能贡献很小，但它显着降低了突出的 PIN7a 活性，这是正确的幼苗顶端钩形成和生长素介导的热带反应所必需的。
• 我们的结果将 PIN 家族的可变剪接确立为一种保守的、功能相关的机制，揭示了生长素介导的植物发育的额外调控水平。