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以苹果矮化砧木M9和乔化砧木MM106为材料,克隆到一个3 753 bp的核苷酸序列,其编码1 250个氨基酸,含有两个ABC_membrance结构域,两个ABC_tran结构域,与梨、油菜和拟南芥的ABCB19基因高度同源,命名为MdABCB19。该序列在M9和MM106中存在一个非同义SNP,编码氨基酸由A突变为S,导致M9α螺旋少了一段。表达量分析表明,MdABCB19在砧木M9和MM106、长富2号/M9和长富2号/MM106均差异表达。启动子序列分析发现M9的MdABCB19启动子在起始密码子上游170 bp处有6个碱基(CTCTGT)缺失,导致缺失一个5’UTR Py-rich stretch motif。MM106的MdABCB19启动子活性高于M9,并且受光照调控。推测M9的MdABCB19启动子5’UTR Py-rich stretch motif缺失可能与其MdABCB19低表达有关;而氨基酸突变导致蛋白质三级结构α螺旋结构改变是否影响生长素运输,有待进一步研究。上述研究表明苹果MdABCB19可能通过调控生长素转运参与砧木苗矮化性状的调控。
The apple dwarf rootstock M9 and Qiaohua rootstock MM106 were cloned into a 3 753 bp nucleotide sequence encoding 1 250 amino acids with two ABC_membrance domains and two ABC_tran domains, And Arabidopsis ABCB19 gene highly homologous, named MdABCB19. This sequence contains a non-synonymous SNP in M9 and MM106. The encoded amino acid changes from A to S, resulting in a reduction of the M9α helix. Expression analysis showed that MdABCB19 was differentially expressed in rootstocks M9 and MM106, Changfu 2 / M9 and Changfu 2 / MM106. Promoter sequence analysis found that M9 MdABCB19 promoter 170 bp upstream of the start codon 6 base (CTCTGT) deletion, resulting in the deletion of a 5’UTR Py-rich stretch motif. The MdABCB19 promoter activity of MM106 is higher than M9 and regulated by light. It is speculated that the deletion of Py-rich stretch motif of MdABCB19 5’UTR may be related to the low expression of MdABCB19 in M9. It is for further study whether the amino acid mutation leads to the change of α-helical structure of protein tertiary structure. The above study shows that apple MdABCB19 may be involved in the regulation of dwarfing traits by controlling the auxin transport.