二穗短柄草异戊烯基转移酶(IPT)编码基因的进化及功能分析  

Evolutionary Analysis and Functional Characterizations of IPT Genes in Brachypodium distachyon

作　　者：周雪[1] 李嘉[1] 李艳花[1] 李婷婷[1] 王中华[1] 权力[1] 

机构地区：[1]西北农林科技大学农学院,陕西杨凌712100

出　　处：《麦类作物学报》2016年第3期273-280,共8页Journal of Triticeae Crops

基　　金：陕西省自然科学基金项目(2014JQ3095);陕西省遗传育种新技术团队项目(2014KCT-25);中央高校基本科研业务费专项(Z109021426)

摘　　要：细胞分裂素(CTK)是一类重要的植物激素,主要作用是引起细胞分裂,诱导芽的形成和促进芽的生长。此外,CTK能够通过参与细胞分化来调控根分生组织大小,对根系生长有负调控作用。异戊烯基转移酶(IPT)是CTK合成过程中的一个关键的限速酶,在高等植物中均以多同源拷贝形式存在。为了探寻二穗短柄草IPT基因的进化起源,并阐明同源基因间潜在的功能分化及其在根系生长过程中的生物学功能,首先,对拟南芥及二穗短柄草的IPT基因进行了序列比对和进化分析,其次,利用荧光定量的方法对二穗短柄草中各IPT基因在不同组织不同发育阶段的转录水平进行了定量分析,最后,通过构建IPT基因RNAi的表达载体,对二穗短柄草中多个IPT基因的转录进行了沉默干扰。结果表明,tRNA-IPT可能代表了IPT祖先基因的功能,而且是ATP/ADP-IPT基因的供体基因。二穗短柄草各IPT基因具有一定的组织表达特异性,大部分ATP/ADP-IPTs处于转录不活跃状态,而tRNA-IPTs在根部和叶部的表达量都很高。因此,IPT基因在单子叶模式植物二穗短柄草中可能采用了不同于拟南芥的方式发挥功能,其主要的发挥功能形式是tRNA类型。二穗短柄草转IPT-RNAi植株表现出根系增强的表型,说明在根系早期发育阶段,二穗短柄草ATP/ADP型IPT基因起到了一定的调节作用。由于IPT基因在早熟禾亚科物种中较为保守,本研究可为增强麦类作物根系发育与提高抗旱性提供必要理论基础。Cytokinin（CTK）is one of the most important plant hormones,causing cell divisions and promoting shoot emergence and development.In addition,CTK plays a negative regulatory role in root growth by engaging through the cell differentiation process within root meristem.In plants,CTK is primarily synthesized by agroup of isopentenyl transferases（IPTs）that are encoded by multiple homologous IPTgenes.To figure out the evolutionary origin of IPT genes,sequence comparisons and phylogenetic analysis were carried out using full length IPT protein sequences from Arabidopsis and Brachypodium distachyon.Moreover,qPCR experiment was conducted to investigate the transcription levels of each IPTgene in Brachypodium distachyon,providing an overall picture of their functional divergences.To further look into their biological functions,an RNAi approach was employedtargeting the conserved coding regions of these IPTgenes.The results showed that,tRNA-IPTis inferred to be the ancestral gene of IPT and the gene donor of ATP/ADP-IPT.Phenotype resulted from the suppressed expressions of IPTgenes allowed insightful understandings of their physiological functions.It was found that IPT genes were preferentially expressed in various tissues.Although most of the ATP/ADP-IPTs were low in the transcription level,the tRNA-IPTs were highly expressed in both root and leaf,suggesting that the tRNA type IPTs might play apredominant role during Brachypodium distachyon root development,which was different from that in Arabidopsis.IPTRNAi plants exhibited enhanced root system phenotypes.It was inferred ATP/ADP-IPTs played a regulatory role in the early development stage of root in Brachypodium distachyon.Because IPT genes are fairly conserved among Pooideae species,our research may provide a theoretical base for the genetic improvement of root in Triticeae crops,thereby advancing their drought tolerance.

关 键 词：二穗短柄草 IPT基因 细胞分裂素 RNAI 根系 

分 类 号：S512.1[农业科学—作物学] S330