Opaque2转录因子对玉米α-醇溶蛋白基因家族成员表达的影响

Differential expression of α-zein family genes regulated by Opaque2 transcription factor

醇溶蛋白是玉米主要的储存蛋白,其中α-醇溶蛋白含量最为丰富,对玉米籽粒品质有重要影响。本研究利用全基因组数据鉴定α-醇溶蛋白基因家族,并从基因保守motif、玉米籽粒不同发育时期基因的表达谱以及转录因子Opaque2对该家族成员表达的影响3个方面分析玉米α-醇溶蛋白基因家族。结果显示,玉米参考基因组中存在39个α-醇溶蛋白基因,其中z1A、z1B、z1C和z1D 4个亚族成员分别为12个、8个、14个和5个。基因保守motif分析发现该家族基因序列高度保守。表达谱分析结果显示该家族表达模式差异较大,其中z1A亚族在籽粒发育时期表达量最高。利用RNA-seq数据剖析在种子发育阶段Opaque 2(O2)野生型和突变体编码该家族成员的表达差异,结果显示O2突变体中z1C亚族成员表达显著下调,z1A亚族表达略有下调,z1B和z1D亚族成员表达量没有显著的变化。本研究在重新注释α-醇溶蛋白家族成员信息的基础上,对该家族的表达谱进行了分析,为今后玉米籽粒品质育种提供了必要遗传信息。

Zein proteins are main repository of nitrogen, which comprise approximately 50% of the total proteins in mature kernels. Zein proteins can be divided into four groups based on their molecular weights,α,β,γandδzeins. In con?trast to the β,γ and δ zeins which were encoded by relatively small gene families,α?zein proteins have four different gene sub?families ( z1A, z1B, z1C, and z1D) and about 39 genes on maize B73 genome.α?zeingene expression profiling analysis showed that their expression patterns diverged greatly and z1A had the highest expression level. Conserverd motif analysis re?vealed α?zein gene family was highly conserved. Opaque 2 mutant, carrying a leucine?zipper motif, downregulates α?zein genes expression, resulting in a so called opaque phenotype, which is widely employed in the creation of germplasm to develop quality protein maize because of the increased lysine and tryptophan accumulation. However, expression analyses of specific gene member ofα?zein reg? ulated by Opaque 2 were not well characterized. In this study, RNA?seq was employed to dissect the individual gene expres?sion at seed developing stages and compared mRNA abundance between wild type and Opaque 2. The results exhibited that Opaque 2 majorly downregulated the expression of z1C subfamily, slightly reduced z1A genes expression, and played insig?nificant roles in z1B and z1D genes expression. Together with the genome annotation of α?zein family and their responding expression profiling, the study implied the genetic information for future improvement of maize grain quality.