茶树生长素受体基因CsTIR1的克隆与表达分析

摘要

吲哚-3-乙酸（又称IAA或生长素），在植物生长发育中具有重要的调控作用，其作用主要通过信号转导途径来完成。生长素受体是其信号转导的关键元件之一。本研究通过 RACE 克隆，获得了茶树中生长素受体CsTIR1基因的 cDNA全长序列（NCBI登录号：JX050147）。CsTIR1序列全长2315 bp，含1746 bp的完整开放阅读框，编码581个氨基酸，预测分子量65.18 kD，理论等电点（pI）5.64。茶树CsTIR1与烟草TIR1的相似性最高达82%，亲缘关系最近。CsTIR1含有1个F-box结构域和6个LRR结构域，三级结构形如“蘑菇状”。CsTIR1在茶树的根、茎、叶和花中具有组织表达特异性；其表达受IAA诱导，3种不同浓度的IAA均能诱导 CsTIR1上调表达，且在50μmol·L-1浓度下表达量最大；ABA、GA3、MeJA 和 BR等激素也能够显著上调其表达；CsTIR1在越冬休眠芽中的表达量低，在活跃期中上调表达。%Indole-3-acetic acid(IAAor auxin),functioning via its signal transduction,playsa pivotal role in plant growth and developmentregulation.Transport inhibitor response 1 (TIR1)protein,anauxin receptor,is one ofthe most critical components in IAA signalingpathway.The full-length cDNA sequence ofCsTIR1genewas obtained by using RACE technique, and submitted to GenBank with accession numberJX050147. TheCsTIR1cDNAlengthwas 2315bp, andcontained a1746bpopen reading frame (ORF), encoding581amino acid residues. The molecular weight and theoretic isoelectric point of CsTIR1 protein are65.18kDand 5.64, respectively.In addition, CsTIR1 proteinhad the highestsequence similarityabout 82%and the closest genetic relationship toNicotiana tabacum.The CsTIR1 was predicted to contain one F-box and six leucine-rich-repeat (LRR) domains, which forming the‘stem’ and‘cap’, respectively.And its tertiary structure isshaped as amushroom.Semi-quantitativeRT-PCRresults suggested thatCsTIR1expressionshowed a tissue-specificity among root, stems, leaves and flowers. The further investigation indicated that the transcript ofCsTIR1was regulated by phytohormones. In a time-course assay,it was found thatCsTIR1was significantly up-regulated whentea plant treated withthreedifferentIAAconcentrationand various plant hormones(ABA, GA3, MeJA and BR), andshowedthe highestexpressionlevelunder50μmol·L-1IAA concentration. Finally,the expression ofCsTIR1was detectedin bud dormancy-active cycle during winter and CsTIR1showeda low transcription level in dormant buds but expressed abundantly in active buds.