高粱LKR基因结构及在种子发育中的表达特征分析

Analysis of the Structure and Expression Characteristics of Sorghum LKR Gene in Seed Development

高粱是优质的酿造原料和饲料作物,但高粱籽粒中缺乏赖氨酸,影响了高粱的营养价值,其中,赖氨酸酮戊二酸还原酶/酵母氨酸脱氢酶(LKR/SDH)是赖氨酸降解途径的关键酶。为修饰赖氨酸酮戊二酸还原酶、减少赖氨酸的降解、提高高粱籽粒营养品质的研究提供数据支持,基于高粱基因组数据库,应用生物信息学方法分析了高粱LKR基因的结构、保守结构域等,预测了其蛋白的二级、三级结构、理化性质和系统进化关系,并采用实时荧光定量PCR检测LKR基因在高粱种子不同发育阶段的表达特性。结果表明,高粱LKR基因定位在4号染色体上,有4个保守结构域。预测结果发现,高粱LKR蛋白二级结构主要为α-螺旋,其三级结构为α-β结构类型;该蛋白是亲水的不稳定蛋白,无跨膜结构,并且没有信号肽,属于非分泌蛋白。此外,高粱LKR蛋白有14种蛋白激酶位点,磷酸化的位点主要是丝氨酸Ser(45个)、苏氨酸Thr(37个)、酪氨酸Tyr(12个)。系统进化树分析表明,高粱与玉米的ZmLKR基因相似性达94.33%。通过qRT-PCR分析发现,授粉后20 d的高粱籽粒中LKR基因表达量最高。

Sorghum is a high-quality brewing material and feed crop,but the lack of lysine in sorghum grains affects the nutritional value of sorghum.Lysine ketoglutarate reductase/saccharopine dehydrogenase(LKR/SDH)is a key enzyme in the lysine degradation pathway.In order to provide data support for the research on modifying lysine ketoglutarate reductase,reducing the degradation of lysine,and improving the nutritional quality of sorghum grains.Based on sorghum genome database,bioinformatics methods were used to analyze the structure of and conservative domain of sorghum LKR gene,predict its secondary and tertiary structure,physical and chemical properties,and evolutionary relationship.The expression characteristics of LKR gene in different developmental stages of sorghum seeds were detected by real-time fluorescent quantitative PCR.The results showed that sorghum LKR gene was located on chromosome 4 and had four conserved domains.Prediction resuls found that the secondary structure of sorghum LKR protein was mainlyα-Helix,and the tertiary structure wasα-βstructure type.The protein belonged to a hydrophilic,unstable protein with no transmembrane structures or signal peptides,and was a nonsecretory protein.Additionally,there were 14 protein kinase sites for sorghum LKR protein,and the phosphorylation sites were mainly serine(45),threonine(37),and tyrosine(12).The phylogenetic tree analysis revealed that similarity of ZmLKR gene between sorghum and maize was 94.33%.Analysis of qRT-PCR showed that the expression of LKR gene reached the highest in sorghum grains 20 days after pollination.