玉米穗发芽突变体vp2的基因克隆及功能研究

Cloning and functional analysis of viviparous mutant vp2 in maize

玉米穗发芽是指籽粒在果穗上未脱离母体时胚芽便开始萌发生长,穗发芽会严重影响玉米的产量和品质。因此高效挖掘和利用优良基因,培育抗穗发芽玉米品种对我国农业生产非常重要。本研究中的玉米穗发芽突变体vp2具有明显的穗发芽表型且性状能稳定遗传,受隐性单基因控制。通过分析vp2突变体基因组序列发现突变体中2个编码基因(Zm00001d015355和Zm00001d015356)存在缺失,Zm00001d015356编码对羟基苯丙酮酸双加氧酶(ZmHPPD1)。hppd1突变体表现穗发芽表型,且与vp2杂交后代中正常与穗发芽籽粒符合3∶1遗传分离比,结果表明Vp2编码ZmHPPD1基因。为进一步分析ZmHPPD1调控籽粒穗发芽的机制,我们检测了突变体中内源激素和ABA合成通路代谢物含量的变化,发现与正常籽粒相比,穗发芽籽粒中ABA含量显著下降,八氢番茄红素显著积累,且紫黄质、玉米黄质和叶黄素含量显著降低。这表明ZmHPPD1通过影响八氢番茄红素向番茄红素的转化,使ABA合成受阻,导致玉米籽粒打破休眠提前萌发。以上研究结果为解析玉米穗发芽的机制提供了基因资源。

Maize vivipary,the precocious germination of seeds on the ear,significantly impacts maize yield and quality.Develop-ing vivipary-resistant maize varieties through the discovery of novel genes is crucial for agricultural production in China.In this study,the maize mutant vp2 exhibited a clear viviparous phenotype with stable inheritance,controlled by a single recessive gene.Genome sequence analysis of the vp2 mutant revealed deletions in two coding genes(Zm00001d015355 and Zm00001d015356),with Zm00001d015356 encoding p-hydroxypyruvate dioxygenase(ZmHPPD1).The hppd1 mutant also displayed a viviparous phenotype.Furthermore,test crosses between vp2 and hppd1 heterozygous plants showed a 3:1 segregation ratio between normal and viviparous kernels,suggesting that ZmHPPD1 is the candidate gene for vp2.To further investigate the mechanism by which ZmHPPD1 regulates maize vivipary,we analyzed endogenous hormone and metabolite content in the ABA synthesis pathway.The results indicated a significant decrease in ABA levels,a substantial accumulation of octahydro lycopene,and a notable reduc-tion in purple xanthophyll,zeaxanthin,and lutein in viviparous kernels.ZmHPPD1 disrupts ABA synthesis by affecting the con-version of octahydro lycopene to lycopene,leading to the loss of dormancy and early germination of maize kernels.These find-ings provide valuable genetic resources for breeding vivipary-resistant maize.