Landau Udi, Asis Lior, Eshed Williams Leor
The Robert H. Smith Institute of Plant Sciences & Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
PLoS One. 2015 May 6;10(5):e0125408. doi: 10.1371/journal.pone.0125408. eCollection 2015.
In angiosperms, the production of flowers marks the beginning of the reproductive phase. At the emergence of flower primordia on the flanks of the inflorescence meristem, the WUSCHEL (WUS) gene, which encodes a homeodomain transcription factor starts to be expressed and establishes de novo stem cell population, founder of the floral meristem (FM). Similarly to the shoot apical meristem a precise spatial and temporal expression pattern of WUS is required and maintained through strict regulation by multiple regulatory inputs to maintain stem cell homeostasis. However, following the formation of a genetically determined fixed number of floral organs, this homeostasis is shifted towards organogenesis and the FM is terminated. In here we performed a genetic study to test how a reduction in ERECTA, CLAVATA and class III HD-ZIP pathways affects floral meristem activity and flower development. We revealed strong synergistic phenotypes of extra flower number, supernumerary whorls, total loss of determinacy and extreme enlargement of the meristem as compared to any double mutant combination indicating that the three pathways, CLV3, ER and HD-ZIPIII distinctively regulate meristem activity and that they act in parallel. Our findings yield several new insights into stem cell-driven development. We demonstrate the crucial requirement for coupling floral meristem termination with carpel formation to ensure successful reproduction in plants. We also show how regulation of meristem size and alternation in spatial structure of the meristem serve as a mechanism to determine flower organogenesis. We propose that the loss of FM determinacy due to the reduction in CLV3, ER and HD-ZIPIII activity is genetically separable from the AGAMOUS core mechanism of meristem termination.
在被子植物中，花的产生标志着生殖阶段的开始。在花序分生组织两侧出现花原基时，编码同源结构域转录因子的WUSCHEL（WUS）基因开始表达，并从头建立干细胞群体，即花分生组织（FM）的奠基者。与茎尖分生组织类似，WUS需要精确的时空表达模式，并通过多种调控输入的严格调控来维持，以保持干细胞的稳态。然而，在形成遗传决定的固定数量的花器官后，这种稳态转向器官发生，FM终止。在这里，我们进行了一项遗传学研究，以测试ERECTA、CLAVATA和III类HD-ZIP途径的减少如何影响花分生组织的活性和花的发育。与任何双突变组合相比，我们发现了额外花数量、额外轮数、确定性完全丧失和分生组织极度增大的强烈协同表型，表明CLV3、ER和HD-ZIPIII这三条途径分别调控分生组织活性，且它们并行发挥作用。我们的研究结果为干细胞驱动的发育提供了几个新的见解。我们证明了将花分生组织终止与心皮形成耦合以确保植物成功繁殖的关键要求。我们还展示了分生组织大小的调控和分生组织空间结构的改变如何作为决定花器官发生的一种机制。我们提出，由于CLV3、ER和HD-ZIPIII活性降低导致的FM确定性丧失在遗传上与分生组织终止的AGAMOUS核心机制是可分离的。
