桑树叶酰聚谷氨酸合成酶基因的克隆及表达分析

Cloning and Expression Analysis of Folypolyglutamate Synthase Gene in Mulberry

对桑树叶酰聚谷氨酸合成酶(folylpolyglutamate synthetase,FPGS)基因进行克隆,获得2个桑树FPGS基因(分别命名为MaFPGS1和MaFPGS2),其编码区分别编码543、558个氨基酸,推导蛋白质分子质量分别为60.3和61.8 kD,pI值分别为5.73和6.02。MaFPGS1与MaFPGS2的氨基酸序列相似度约为49.80%,MaFPGS1与川桑同源蛋白FPGS(XP_010108389.1)的序列相似度为97.60%,MaFPGS2与川桑同源蛋白FPGSiX4(XP_024025432.1)的序列相似度为91.79%。MaFPGS1和MaFPGS2各自聚在1个分支,二者与枣(Ziziphus jujuba)的FPGS亲缘关系都最近。MaFPGS1和MaFPGS2在桑树嫩叶中的表达量最高,根中表达量最低。在桑树种子萌发过程中,MaFPGS1的表达量比MaFPGS2更高,且在吸水后10 d子叶完全展开时达到最高。在桑树离体再生根系中,MaFPGS2的表达量比MaFPGS2更高,且在诱导7 d后表达就明显上调,而MaFPGS1的表达在诱导15 d后才显著上调,推测MaFPGS可能参与根系形成。桑树再生植株受到轻度低氮胁迫时,MaFPGS的表达量显著增加。研究结果为进一步解析MaFPGS基因的功能奠定了基础。

In this study,mulberry genes encoding folylpolyglutamate synthetase(FPGS)were cloned,and two mulberry FPGS were obtained and named as MaFPGS1 and MaFPGS2 which encoded 543 amino acids and 558 amino acids,respectively.The protein molecular weight of MaFPGS1 and MaFPGS2 were predicted to be 60.3 kD and 61.8 kD and their pI were 5.73 and 6.02,respectively.The sequences identity between MaFPGS1 and MaFPGS2 was only 49.80%.MaFPGS1 and homologous protien FPGS(XP_010108389.1)in Morus notabilis shared 97.60%sequence identity,while MaFPGS2 and homologous protein FPGSiX4(XP_024025432.1)in Morus notabilis shared 91.79%sequence identity.MaFPGS1 and MaFPGS2 clustered into separate branches,and both had a close relationship with the FPGS of Ziziphu sjujuba.Besides,expression levels of MaFPGS1 and MaFPGS2 were the highest in the tender leaves and the lowest in the roots of mulberry trees.During the germination of mulberry seeds,the expression level of MaFPGS1 was higher than that of MaFPGS2,and reached the highest when the cotyledons fully expanded at 10th day after water absorption.In mulberry regenerated roots,expression level of MaFPGS2 was higher than that of MaFPGS1 and was significantly up-regulated at 7 d after induction,while that of MaFPGS1 was significantly up-regulated at 15 d after induction.It was suggested that both MaFPGS genes were involved in root formation.After the regenerated mulberry tree was exposed to low nitrogen stress,the expression levels of MaFPGS genes increased significantly.These results will be helpful for further study on the function of MaFPGS genes.