背景回顾：Flowers are produced by floral meristems, groups of stem cells that give rise to floral organs. In grasses, including the major cereal crops, flowers (florets) are contained in spikelets, which contain one to many florets, depending on the species. Importantly, not all grass florets are developmentally equivalent, and one or more florets are often sterile or abort in each spikelet. Members of the Andropogoneae tribe, including maize (Zea mays), produce spikelets with two florets; the upper and lower florets are usually dimorphic, and the lower floret is greatly reduced compared to the upper floret. 

研究对象：In maize ears, early development appears identical in both florets but the lower floretultimately aborts. 

主要研究：To gain insight into the functional differences between florets with different fates, we used laser capture microdissection coupled with RNA-seq to globally examine gene expression in upper and lower floral meristems in maize.

结果1-差异表达基因富集：Differentially expressed genes were involved in hormone regulation, cell wall, sugar and energy homeostasis. Furthermore, cell wall modifications and sugar accumulation differed between the upper and lower florets. 

结果2-边界域：Finally, we identified a boundary domain between upper and lower florets, which we hypothesize is important for floral meristem activity. 

结果3-模型：We propose a model in which growth is suppressed in the lower floret by limiting sugar availability and upregulating genes involved in growth repression. 

结论：This growth repression module may also regulate floret fertility in other grasses and potentially be modulated to engineer more productive cereal crops.

 摘 要 

花是由花分生组织产生的，而花分生组织是一类干细胞群，主要产生各个花器官。在包括主要的谷类作物的禾本科植物中，花（小花）包含在小穗中，每个小穗含有一至多个小花，含有的小花数量以物种而不同。重要的是，并不是所有禾本科植物的小花在发育上是相同的，并且每个小穗中经常有一个或者多个小花是不育的或者发育中止。禾本科蜀黍族包括了玉米，该族植物产生的小穗含有两朵小花；上位和下位小花通常是二型的，并且与上位小花相比，下位小花数量明显较少。在玉米穗中，两朵小花的早期发育近乎一致，但是下位小花最终会败育。为了理解不同命运的小花之间在功能上的差异性，作者利用激光捕获显微切割和RNA-seq技术来获取上位和下位小花花分生组织的基因表达谱。差异表达基因主要富集于激素调控、细胞壁、蔗糖和能量内稳态。此外，细胞壁修饰和蔗糖积累在上位和下位小花之间差异显著。最终，作者鉴定了上位和下位小花之间的边界，作者认为这对于花分生组织活性是非常重要的。作者提出了一个模型，其中下位小花中蔗糖会被抑制，参与生长抑制相关的基因会被激活，从而下位小花的发育受到抑制。这种生长抑制模块也可能调节其它禾本科植物的小花繁育性，并存在用于培育高产谷物工程育种的潜在应用价值。

 通讯作者 

** Beth E Thompson **