两个相关基因表达量和SNP与玉米雄穗大小相关

Association of expression amount and SNP of two candidate genes to tassel size in maize

玉米雄穗通常较发达，散粉量大于授粉需要，过量消耗能量会影响光合产物向果穗的分配，过于发达的雄穗还会影响群体透光性、降低光合效率。生产实践和育种研究证明，由于雄穗大小与玉米籽粒产量负相关，因此成为品种选育的间接选择指标。该研究根据前人的报道，从11个雄穗大小不同的玉米自交系中扩增角蛋白相关蛋白基因幽尸5—4和受体样蛋白激酶基因CLV1的基因组序列，多重比较后用以分析其开放阅读框、保守结构和单核苷酸多态性，用荧光实时定量PCR检测其在雄穗原基中的差异表达，并与雄穗分枝数和雄穗干重两个度量雄穗小的指标进行了相关分析。结果表明：KAP5—4基因的相对表达量与雄穗分枝数（r=0．77，P〈0．01）和雄穗干重正相关（r=0．83，P〈0．01）。11个自交系的CLV1基因开放框在2104bp存在单核苷酸多态性，其中5个自交系的2014～2016bp核苷酸组成密码子GAC，编码受体样蛋白第702位酸性的天冬氨酸，另6个自交系的2014～2016bp核苷酸组成密码子AAC，编码受体样蛋白第702位极性天冬氨酰胺。在前5个自交系中，CLV1基因的相对表达量与雄穗分枝数（r=-0．92，P〈0．01）和雄穗干重（r=-0．91，P〈0．05）负相关：而在后6个白交系中，仅与雄穗干重负相关（r=-0．91，P〈0．05）。综上所述，KAP5—4和CLV1基因的表达和单核苷酸多态性与玉米雄穗大小关系密切，可开发功能性的DNA标记用于玉米育种的分子标记辅助选择。

Maize tassel usually sheds powders much more than the requirement of pollination. Tile overdeveloped tassel not only consumes excessive energy, preventing the transferring of photosynthate to the developing ear, but also decrea- ses the sunlight transmittance of the population, resulting in photosynthetic rate decrease. Therefore, tassel size becomes an indirect selection criterion in maize variety selection because its negative correlation with grain yield was found in maize production practice and breeding study. According to previous reports, the genomic sequences of the keratin-asso- ciated protein gene KAP 5-4 and the receptor-like protein kinase gene CLV1 were amplified piece by piece from eleven maize inbred lines with different tassel size, and used for the analysis of multiple alignment, open reading frames, do- main structures, and single nucleotide polymorphism. Their differential expressions in tassel primordial among these in- bred lines were detected by fluorescence real-time quantitative PCR, and used for correlation analysis with tassel size measured by number of primary branch and dry weight of tassel. The results showed that the relative expression amount of the KAP 5-4 gene was positively correlated with number of primary branch （r = 0.77, P〈0.01 ） and dry weight of tassel （r= 0.83, P〈0.01 ）. A single nucleotide polymorphism at the 2 104 bp base of the open reading frame of the CLV1 gene from eleven maize inbred lines consisted codon GAC encoding acidic aspartic acid at the 702nd site of the receptor-like protein kinase at the 2 104 to 2 016 bp base in five of the inbred lines, and consisted codon AAC encoding polar aspara- gine at the same site in the other six inbred lines. The relative expression amount of the CLV1 gene was negatively corre- lated with number of primary branch （r=-0.92, P〈0.01） and dry weight of tassel （r=-0.91, P〈0.05） within the for- mer five inbred lines, and negatively correlated only with dry weight of tassel （r =-0.91, P〈0.05） within the later six inbred lines. It was concluded that the expression and single nucleotide polymorphism of the KAP 5-4 and CLV1 genes were closely associated with tassel size of maize inbred lines, and functional DNA markers can be developed for DNA marker-assisted selection in maize breeding.