高羊茅腺苷甲硫氨酸脱羧酶基因FaSAMDC的克隆与差异表达分析

Cloning and differential expression analysis of S-adenosylmethionine decarboxylase gene FaSAMDC in tall fescue

在进行高羊茅光敏色素C基因5′端克隆时,筛选到腺苷甲硫氨酸脱羧酶基因的5′端序列,根据5′端序列设计引物,扩增出该基因的3′端,拼接得到高羊茅腺苷甲硫氨酸脱羧酶基因全序列,命名为FaSAMDC（GenBank登录号：HQ606139）,利用实时荧光定量PCR技术研究FaSAMDC基因在长日照与短日照条件下昼夜24 h的表达差异,为进一步揭示不同光周期调控FaSAMDC基因的表达奠定理论基础。FaSAMDC的cDNA全长1 964 bp,具有微型上游阅读框、小型上游阅读框和主阅读框3个开放阅读框,分别位于226-234,234-380和555-1 742 bp,微型上游阅读框和小型上游阅读框存在1个碱基重叠,主阅读框编码395个氨基酸,含有保守功能域：酶原剪切位点功能域和SAMDC蛋白快速降解有关的PEST功能域。对编码蛋白氨基酸序列的同源性分析表明,FaSAMDC与其他单子叶植物SAMDC蛋白的亲缘关系较近。在长日照和短日照处理条件下,FaSAMDC都具有3个表达峰。短日照处理条件下的表达峰比长日照处理条件下的表达峰早几个小时,但峰高低于长日照条件。由此说明,FaSAMDC基因的表达受光周期调控,与生物钟控制的昼夜节律有关。

We screened 5′ end sequence of S-adenosylmethionine decarboxylase gene when identified 5′ end sequence of phytochrome C gene from tall fescue.The primers were designed and amplified 3′ end sequence based on the 5′ end sequence of S-adenosylmethionine decarboxylase gene,5′ end sequence and 3′ end sequence were jointed,a SAMDC of cDNA from tall fescue has been identified,and designated as FaSAMDC（GenBank Accsssion： HQ606139）.Theoretical basis of different photoperiods regulated FaSAMDC expression was provided through a study of FaSAMDC differentially expressed during 24 hours in long-days and short-day using real-time fluorescence quantitative PCR.The cDNA of FaSAMDC is 1 964 bp in length and contains three open reading frames,tiny upstream ORF（226-234 bp）,small upstream ORF（234-380 bp）,main ORF（555-1 742 bp） respectively.Main ORF encodes a protein of 395 amino acids.Domain analysis reveals that proteins encoded by FaSAMDC genes contain two conserved domains： Proenzyme splice site domains and involving SAMDC protein rapid degradation PEST domain.FaSAMDC showed a close genetic relationship with the known SAMDC of monocotyledonous plants.Three expression peaks was detected in both long days and short days condition.The level of FaSAMDC expression peak under long days was significantly higher than that under short days.However,the peak of FaSAMDC transcription level under short days condition was earlier several hours than that of long days condition.This indicates that FaSAMDC gene transcripted with a circadian rhythm and was regulated by photoperiod.