杧果乙烯受体基因MiETR1b的分离与表达分析

以‘紫花杧’杧果（Mangifera indica L.‘Zihua’）子叶切段为材料，采用RT-PCR结合RACE方法得到乙烯受体基因ETR1的cDNA及基因组DNA全长，命名为MiETR1b。该基因cDNA全长2 530 bp，开放读码框为2 220 bp，编码739个氨基酸；其基因组DNA全长4 116 bp，其中从起始密码子到终止密码子为3 305 bp，含有6个外显子和5个内含子。氨基酸序列多重比对及系统发育树结果显示MiETR1b与MiETR1亲缘关系最近，与CsERS1、DlETR1、TcERS1、PtrETR1有较高的同源性，且具有保守的GAF域和组氨酸激酶域。这些结果表明，MiETR1b为ETR1家族同源基因。荧光定量PCR结果表明，MiETR1b在杧果子叶切段不定根形成过程中在远轴端和近轴端都有表达，其中远轴端0.25 ~ 2 d的表达量显著上调；吲哚丁酸（IBA）和2,3,5–三碘苯甲酸（TIBA）预处理后分别在1 d和6 h显著下调。另一方面，在培养的初期，即0.5 ~ 1 d，乙烯释放量相对较高，4 d及其以后的乙烯释放量急剧下降，表明杧果子叶切段不定根形成过程中有较多乙烯生成，提示MiETR1b可能参与了不定根的形成。

Isolation and Expression Analysis of an Ethylene Receptor Gene MiETR1b in Mango

A mango ETHYLENE RESPONSE1（ETR1）gene，designated as MiETR1b，was isolated from the cotyledon of mango（Mangifera indica L.‘Zihua’）using RT-PCR and RACE. The full-length cDNA was 2 530 bp with an open reading frame of 2 220 bp，encoding a putative protein of 739 amino acids. The genomic DNA sequence of MiETR1b was 4 116 bp long with a sequence of 3 305 bp from start codon to terminator codon containing six exons and five introns. The deduced amino acids possessed conserved domains of GAF and HATPase_c superfamily. Phylogenetic tree analysis indicated that MiETR1b had the highest similarity with MiETR1 from M. indica，and had high similarity with CsERS1，DlETR1，TcERS1 and PtrETR1. Quantitative real-time PCR showed that MiETR1b expressed in proximalcut surface or distal cut surface throughout the adventitious root formation period. Meanwhile，the expression of MiETR1b in distal cut surface was significantly up-regulated within 0.25–2 days. Howeve，pre-treatment with indole-3-butyric acid（IBA）and 2,3,5-triiodobenzoic acid（TIBA）significantly down-regulated MiETR1b expression of 1 day and 6 hours，respectively. On the other hand，more ethylene produced within 0.5–1 day，while the ethylene production decreased after 4 days of culture. In conclusion，MiETR1b might play an important role during the adventitious root formation of mango cotyledon segments，which was related to ethylene production.