扁蓿豆SWEET基因家族鉴定及在干旱和寒冷胁迫下的表达分析

Identification of SWEET Gene Family in Medicago ruthenica and Expression Analysis under Drought and Cold Stress

SWEET(Sugars will eventually be exported transporter)蛋白是一类新型糖转运蛋白。本研究基于扁蓿豆(Medicago ruthenica)基因组对MrSWEET基因家族进行了鉴定和生物信息学分析,并通过qPCR初步分析MrSWEET在干旱和寒冷环境下的表达模式,以期深入探究扁蓿豆SWEET基因家族在非生物胁迫中的作用。结果表明,扁蓿豆SWEET糖转运蛋白家族共有18个成员,都具有典型的MtN3_saliva/PQ-Loop结构域。系统发育分析表明,其可分为4个进化枝,其中CladeⅠ包括MrSWEET1a、-1b、-2a、-2b、-3a、-3b;CladeⅡ包括MrSWEET4~6;CladeⅢ包括MrSWEET9~15,MrSWEET16~17属于CladeⅣ。所有的MrSWEET成员都含有Motif 1、3、4、5,可能与糖转运蛋白的功能有关。MrSWEET基因启动子区域含有多个与光响应、激素响应和非生物胁迫以及植物生长发育有关的功能元件。在干旱(15%PEG6000)和寒冷(4℃)胁迫下,扁蓿豆根部的MrSWEET基因表达水平相对高于叶片,且根部大多数基因在干旱和寒冷胁迫处理6、12 h时表达量最高;干旱处理下,根部的MrSWEET1a和MrSWEET16相对表达量在3、6、12、24 h和7 d时均高于对照,寒冷处理下根部的MrSWEET16表达量以及处理7 d的MrSWEET1a表达量高于对照,说明其可能参与调控扁蓿豆对干旱和寒冷胁迫的响应。

SWEET(Sugars will eventually be exported transporter)is a new type of sugar transporter protein.In this study,the MrSWEET gene family was identified and bioinformatical analyzed based on the genome of Medicago ruthenica,and the expression pattern of MrSWEET in drought and cold environment was preliminically analyzed by qPCR,in order to further explore the role of the SWEET gene family in abiotic stress in Medicago ruthenica.The results showed that there were 18 members in the SWEET sugar transporter protein family of Medicago ruthenica,all of which had MtN3_saliva/PQ-Loop domain.Phylogenetic analysis showed that SWEET sugar transporter protein family in Medicago ruthenica could be divided into four evolutionary branches,among which CladeⅠincluded MrSWEET1a,-1b,-2a,-2b,-3a and 3b;CladeⅡincluded MrSWEET4-6;CladeⅢincluded MrSWEET9-15,and MrSWEET16 and 17 belonged to CladeⅣ.All MrSWEETs contained Motifs 1,3,4,and 5,which might be related to the function of sugar transporters.The MrSWEET genes promoter region contained cis-acting elements related to light response,hormone response,abiotic stress,and plant growth and development.Under drought(15%PEG6000)and cold(4℃)stresses,the expression level of MrSWEET genes in the root of Medicago ruthenica was relatively higher than that in the leaves,and the expression level of most genes in the root was highest at 6 and 12 h under drought and cold stress.The relative expression level of MrSWEET1a and MrSWEET16 in root was significantly upregulated at 3,6,12,24 h and 7 d after drought,and the expression levels of MrSWEET16 and MrSWEET1a at 7 d after cold treatment were higher than CK,suggesting that they might be involved in regulating the response of Medicago ruthenica to drought and cold stresses.