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

花序分生组织（inflorescence meristem，IM）是植物发育过程中的第一个生殖分生组织，为植物的花部变异、花序结构和生产力提供了基础。先前在其他植物模型中的研究表明，操纵IM大小可以诱导植物产生更多的花器官。然而，IM如何调节小麦穗发育和影响产量性状的研究很少。最近，我所在的实验室发现了MADS-box基因的两个显性突变等位基因，短营养期1（SVP 1）和营养向生殖转换2（VRT 2），这导致小麦籽粒花组织和籽粒长度增加。当这两个基因的突变体等位基因组合敲除时，svp 1vrt 2双突变体导致每穗小穗数（SNS）增加70%。我的初步数据表明，TaWOX（WUS相关同源框）表达普遍下降VRT 2高表达显性突变体在早期穗发育阶段，表明VRT 2参与IM维护微调TaWOX基因。结合这些初步结果，我假设增加小麦中IM活性将导致SNS增加，并可能导致产量增加。在本研究中，我将利用svp 1 vrt 2突变体和TaWOX 2转基因株系，结合小麦基因组学和基因编辑方法的最新突破，实现我的三个主要目标：1.确定svp 1 vrt 2突变体中SNS增加是否由IM尺寸增大引起2。阐明TaWOX 2在小麦中建立和维持IM活性的作用3.发现控制小麦IM大小和穗发育的新基因通过这项奖学金，我将大大拓宽小麦IM发育及其与产量相关性的知识，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，提高我的专业成熟度，以实现我的能力和抱负，成为一个独立的研究小组的领导者。

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.