Characterization of <i>MORE AXILLARY GROWTH</i> Genes in <i>Populus</i>

Background Strigolactones are a new class of plant hormones that play a key role in regulating shoot branching. Studies of branching mutants in Arabidopsis, pea, rice and petunia have identified several key genes involved in strigolactone biosynthesis or signaling pathway. In the model plant Arabidopsis, MORE AXILLARY GROWTH1 (MAX1), MAX2, MAX3 and MAX4 are four founding members of strigolactone pathway genes. However, little is known about the strigolactone pathway genes in the woody perennial plants. Methodology/Principal Finding Here we report the identification of MAX homologues in the woody model plant Populus trichocarpa. We identified the sequence homologues for each MAX protein in P. trichocarpa. Gene expression analysis revealed that Populus MAX paralogous genes are differentially expressed across various tissues and organs. Furthermore, we showed that Populus MAX genes could complement or partially complement the shoot branching phenotypes of the corresponding Arabidopsis max mutants. Conclusion/Significance This study provides genetic evidence that strigolactone pathway genes are likely conserved in the woody perennial plants and lays a foundation for further characterization of strigolactone pathway and its functions in the woody perennial plants.背景 独脚金内酯（Strigolactones）是一类新型植物激素，在调控植物枝条分枝过程中发挥关键作用。针对拟南芥、豌豆、水稻及矮牵牛的分枝突变体研究，已鉴定出多个参与独脚金内酯生物合成或信号通路的关键基因。在模式植物拟南芥中，多腋芽生长1（MAX1）、MAX2、MAX3及MAX4是独脚金内酯通路基因的四个经典成员。然而，目前对木本多年生植物中的独脚金内酯通路基因所知甚少。 方法/主要发现 本研究报道了木本模式植物毛果杨（Populus trichocarpa）中MAX同源基因的鉴定工作。我们成功鉴定出毛果杨中各MAX蛋白的序列同源物。基因表达分析显示，毛果杨MAX旁系同源基因在不同组织与器官中呈差异表达模式。此外，本研究证实毛果杨MAX基因能够互补或部分互补对应拟南芥max突变体的枝条分枝表型。 结论与意义 本研究提供了遗传学证据，表明独脚金内酯通路基因在木本多年生植物中大概率具有保守性，为后续深入解析独脚金内酯通路及其在木本多年生植物中的功能奠定了研究基础。