In rice, the spikelet is the basic unit of inflorescence, and its development is important for determining the grain yield and quality. We reported a rice spikelet mutant multi-floret spikelet 4 (mfs4) which resulted in the production of extra floral organs or a whole extra floret, and elongated sterile lemmas. The results suggested that the mutation of the MFS4 gene interfered with spikelet meristem determinacy and floral organ identity. In addition, the plant height and the grain length and width in the mfs4 mutant were all less than those in the wild type. Using the bulked segregant analysis method, the MFS4 gene was localized in a 557-kb region on the long arm of chromosome 1. Sequence analysis showed that there was a C-base deletion at the open reading frame of LOC_Os01g67430. Further tests indicated that a wild type copy of LOC_Os01g67430 was able to reverse the mfs4 defects, which indicated that LOC_Os01g67430 was the MFS4 gene. The MFS4 gene encodes a lipase located in the mitochondria and is expressed strongly in the young inflorescence. qRT-PCR results showed that the expression of some genes that were known to regulate spikelet meristem determinacy and grain size were decreased in the mfs4 mutant, which indicated that the MFS4 gene regulates spikelet meristem determinacy and grain size by modulating the expression of these genes.

在水稻中，小穗是花序的基本单位，它的发育对决定籽粒产量和品质具有重要意义。我们报道了一个水稻小穗突变体多小花小穗 4 ( mfs4 )，它导致产生额外的花器官或一整朵额外的小花，以及拉长的不育外稃。结果表明MFS4基因的突变干扰了小穗分生组织的确定性和花器官特性。此外，mfs4突变体的株高和籽粒长宽均小于野生型。使用批量分离分析方法，MFS4基因定位于1号染色体长臂557kb区域。序列分析显示LOC_Os01g67430的开放阅读框存在C碱基缺失。进一步的测试表明LOC_Os01g67430的野生型拷贝能够逆转mfs4缺陷，这表明LOC_Os01g67430是MFS4基因。该MFS4基因编码位于线粒体脂肪酶，并在年轻花序强烈表达。qRT-PCR 结果表明，在mfs4突变体中，一些已知调节小穗分生组织决定性和晶粒大小的基因表达降低，表明MFS4 基因通过调节这些基因的表达来调节小穗分生组织的决定性和晶粒大小。