Abstract: Indole-3-acetic acid (IAA or auxin), functioning via its signal transduction, plays a pivotal role in plant growth and development regulation. Transport inhibitor response 1 (TIR1) protein, an auxin receptor, is one of the most critical components in IAA signaling pathway. The full-length cDNA sequence of CsTIR1 gene was obtained by using RACE technique, and submitted to GenBank with accession number JX050147. The CsTIR1 cDNA length was 2β315βbp, and contained a 1β746βbp open reading frame (ORF), encoding 581 amino acid residues. The molecular weight and theoretic isoelectric point of CsTIR1 protein are 65.18 kD and 5.64, respectively. In addition, CsTIR1 protein had the highest sequence similarity about 82% and the closest genetic relationship to Nicotiana 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 is shaped as a mushroom. Semi-quantitative RT-PCR results suggested that CsTIR1 expression showed a tissue-specificity among root, stems, leaves and flowers. The further investigation indicated that the transcript of CsTIR1 was regulated by phytohormones. In a time-course assay, it was found that CsTIR1 was significantly up-regulated when tea plant treated with three different IAA concentration and various plant hormones (ABA, GA₃, MeJA and BR), and showed the highest expression level under 50 μmol·L^-1 IAA concentration. Finally, the expression of CsTIR1 was detected in bud dormancy-active cycle during winter and CsTIR1 showed a low transcription level in dormant buds but expressed abundantly in active buds.

Key words: tea plant, phytohormone, auxin, auxin receptor gene CsTIR1, bud-dormancy