Meristem Power: The power of the inflorescence meristem to determine spikelet number per spike in wheat

花序分生组织是植物发育过程中的第一个生殖分生组织，是所有现存花的变异、花序构型和最终生产力的基础。此前在其他植物模型中的研究表明，控制IM大小可以诱导植物产生更多的花器官。然而，IM如何调控小麦的穗部发育和影响产量性状的研究很少。最近，我的宿主实验室发现了MADS-box基因的两个显性突变等位基因，即短营养阶段1(SVP1)和VEGETATUVE to生殖转换2(VRT2)，它们导致小麦籽粒花组织和籽粒长度的增加。当结合这两个基因的敲除突变等位基因时，svp1vrt2双突变导致每穗小穗数(SNS)增加70%。我的初步数据显示，在幼穗发育早期，VRT2高表达的显性突变体中，TaWOX(WUS相关同源盒)的表达普遍下降，这表明VRT2通过微调TaWOX基因参与了IM的维持。结合这些初步结果，我提出了一个假设，即增加小麦的IM活性将导致SNS的增加，并有可能增加产量。在这项建议中，我将使用svp1 vrt2突变体和TawOX2转基因系，并结合最近在小麦基因组学和基因编辑方面的突破来追求我的三个主要目标：1.确定svp1 vrt2突变体中SNS的增加是否是由于IM大小2。阐明TaWOX2在建立和维持小麦IM活性中的作用。发现控制小麦IM大小和穗发育的新基因通过这次奖学金，我将极大地拓宽小麦IM发展及其与产量的相关性的知识，获得技术和可转移技能方面的高级培训和实践经验，扩大我的合作网络，并提高我的专业成熟度，以实现我成为独立研究小组组长的能力和抱负。

The inflorescence meristem (IM) is the first reproductive meristem during plant development, and provides the foundation for all existing floral variation, inflorescence architecture and ultimately productivity. Previously studies in other plant models revealed that manipulating IM size can induce plants to produce more floral organs. However, how IM regulate spike development and influence yield traits in wheat is poorly studied. Recently, my host lab uncovered two dominant mutant alleles of MADS-box gene, SHORT VEGETATIVE PHASE1 (SVP1) and VEGETATUVE TO REPRODUCTIVE TRANSITION2 (VRT2), that lead to increased grain floral tissue and grain length in wheat. When combined knockout mutant alleles of these two genes, with the svp1vrt2 double mutant leading to 70% more spikelet number per spike (SNS). My preliminary data showed that TaWOX (WUS-related homeobox) expression generally decreased in VRT2-high expression dominant mutant at early spike developmental stages, indicating VRT2 involved in IM maintenance by fine tuning TaWOX genes. Combining these preliminary results led me hypothesize that increasing IM activity in wheat will lead to an increase in SNS, and potentially yield. In this proposal, I will use svp1 vrt2 mutants and TaWOX2 transgenic lines and combining the recent breakthroughs in wheat genomics and gene editing approaches to pursue my three main objectives:1. Determine whether increased SNS in svp1 vrt2 mutants is caused by enlarged IM size2. Elucidate the role of TaWOX2 on establishing and maintaining IM activity in wheat3. Uncover novel genes controlling IM size and spike development in wheatThrough this fellowship, I will greatly broaden the knowledge of the wheat IM development and its correlation with yield, gain advanced training and practical experience in technical and transferable skills, expand my collaborative network, and enhance my professional maturity to achieve my competences and ambition to be an independent research group leader.