We identified a new maize viviparous mutant during seed reproduction,designated as vp-like4.This mutant phenotype was steadily inherited and genetically regulated by a single recessive gene.Using an F2 segregation population derived from vp-like4 and inbred line Mo17,we mapped the target gene in an interval from 173.8 to 175.6 Mb on chromosome 5 by the BSR-Seq strategy.Using genomic sequence database,we found that viviparous gene Vp15 is located in this mapping region.The maize Vp15 gene encodes the molybdopterin synthase small subunit,which is required in the process of catalyzing the reaction from carotenoid to ABA.The heterozygous plants from two independent vp15 mutants,vp15-umu1 and vp15-DR1126,were used to cross with vp-like4 heterozygous plants,showing a 3∶1 segregation ratio for normal and viviparous kernels.The genomic sequence analysis revealed that vp-like4 mutant had a 60-bp deletion in the second exon and 3'-untranslated region of Vp15 gene,which is different from vp15-umu1 and vp15-DR1126 both mutated from a Mutator transponson inserting in the second exon of Vp15 gene.Further RT-PCR analysis revealed that the expression level of vp15 was significantly lower in vp-like4.Taken together,these evidences suggest that vp-like4 is a new allele mutant from vp15.%在玉米繁种过程中发现一个玉米穗发芽突变体(viviparous),命名为vp-like4.经过连续多代自交发现该突变体性状能稳定遗传,并且表现为隐性单基因控制.以vp-like4与自交系Mo17杂交构建F2遗传定位群体,利用BSR-Seq方法,将目的基因定位于玉米第5染色体173.8～175.6 Mb之间.通过基因组序列信息分析发现,在此定位区间内存在一个已报道的Vp15基因.Vp15基因编码钼喋呤合酶小亚基,参与类胡萝卜素裂解为ABA的过程.利用2个独立的vp15突变体vp15-umu1和vp15-DR1126的杂合体,分别与vp-like4突变体杂合体做杂交进行等位测验,发现杂交后代中正常籽粒与穗发芽籽粒比例符合3∶1分离比.基因组序列分析发现vp-like4突变体中Vp15基因在第2外显子末端及3'非翻译区有60个碱基的缺失,与所报道的vp15突变体vp1 5-umu1、vp15-DR1126均在第2个外显子有Mutator转座子插入的突变方式不同.进一步通过RT-PCR检测发现,vp-like4突变体中Vp15基因的表达量显著降低.以上实验证据表明,vp-like4是一个新的Vp15基因等位突变体.
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