拟南芥POSR1调控器官大小的作用机制研究

It is an important problem in developmental biology that how plant apperceive and determine the organ size. Moreover, plant organ size is also a significant agricultural character. Therefore, a deeper understanding of regulating mechanism of organ size is essential. In our study, a mutant line which had larger organs was screened from Arabidopsis mutant pool. T-DNA insert site analysis and mutant reversion identifies that the phynotype is induced by a new gene with unknown function (named it as POSR1, plant organ size regulator 1). Preliminary study shows that POSR1 is located in nuclear and determines organ size by regulating cell growth negatively. The regulation of plant organ size is very complicated and the mechanisms are often different in different organs. In this study, we will choose leaf and seed as objects of study to: 1) illustrate the dynamical expression model of POSR1 in Arabidopsis tissues especially the leaf and seed; 2) find the interacting protein and DNA sequence of POSR1 by yeast two hybrid system and CHIP-seq method; 3) analyze the key genes participating the other known pathways regulating organ size by transcriptome sequencing and clarify the relationship between them and POSR1; 4) by compare the difference between the pathways regulating the sizes of leaf and seed, illustrate the action mechanisms of POSR1 gene participating regulation of plant organ size.

植物如何感知并决定其器官大小是一个重要的发育生物学问题，也是农业领域中关注的重点，因此对植物器官大小调控的作用机制研究颇为重要。课题前期利用拟南芥突变体库鉴定出一个各组织器官比野生型明显变大的缺失突变体。插入位点分析和突变体回复确认该表型由一个功能未知的新基因导致（命名为POSR1，plant organ size regulator 1）。初步研究表明，POSR1定位于细胞核并通过负向调节细胞生长影响器官大小。植物器官大小调控复杂且不同器官大小的调控机制也不尽相同。本项目拟选择叶片和种子作为研究对象:1）明确POSR1在拟南芥中的作用部位及动态变化；2）分析寻找POSR1在叶片和种子中的互作蛋白及DNA序列；3）转录组分析已知器官大小调控途径关键基因的表达变化并阐明与其之间的作用关系；4）比较POSR1参与调控叶片和种子大小途径的异同，阐明POSR1参与调控植物器官生长发育的作用机制。

植物如何感知并决定其器官大小是一个重要的发育生物学问题，也是农业领域中关注的重点，因此对植物器官大小调控的作用机制研究颇为重要。本项目针对一个调控器官大小的功能获得性突变体材料posr1进行研究，对该突变体材料以及35S驱动的posr1过表达材料进行产量表型分析发现，该基因的过表达植株的株高、分枝数、整株角果数及角粒数无差异，粒重及种子含油量显著增加，最高可达20%及10%以上。Posr1启动子驱动gus在拟南芥中的表达染色发现，在叶片、根、花器官、角果皮以及种胚种均有表达，但表达量存在一定的差异。posr1突变体叶片转录组测序发现与野生型存在超过1倍差异的高表达基因为362个，低表达基因为311个。GO分析显示，参与生物学过程的主要包括response to stress、signal transduction、transport等；按照分子功能类别分析差异基因主要集中在transcription factor activity、other enzyme activity、transporter activity、hydrolase activity等；按照细胞组分分析差异基因主要集中在cell wall、extracellular、plasma membrane、chloroplast等。MapMan分析显示posr1中高表达基因所参与的途径主要包括metal handling、hormone metabolism、redox、amino acid metabolism development、stress等；低表达基因参与的途径主要包括second metabolism、stress、misc、transport等。对过表达材料的叶片激素含量及光合效率测定发现，与野生型相比，过表达材料中的乙烯含量降低，光合效率增加。利用PUC19-35S-GFP构建POSR1与GFP报告基因的融合蛋白表达载体，亚细胞定位显示POSR1位于细胞核内，且不具有自激活活性，酵母双杂交筛选以及BIFC验证共获得6个与POSR1互作的蛋白，其中存在激素相关蛋白，推测posr1通过调控激素途径相关基因的表达影响细胞分裂及生长从而导致器官变大。该研究对植物器官大小发育调控基因的研究不仅具有重要的理论价值，在实践上也将为通过遗传工程手段提高作物产量等方面提供重要的遗传信息，在作物遗传改良等诸