以苹果幼叶为试验材料，通过同源克隆和RT-PCR方法分离出B＿LECTIN基因家族中的一个基因，命名为MdMBL。分析结果表明，克隆得到的MdMBL长度为1181 bp，包括20 bp的5′非编码区、81 bp的3′非编码区和一个长度为1080 bp编码359个氨基酸的开放阅读框，推测该蛋白质分子量为39．76 kDa，其等电点为8．72。在构建的MBL系统进化树中，MdMBL与葡萄的MBL的关系最近，其次为橹豆的MBL，与苹果的MBL2同源基因进化关系最远。相对荧光定量RT-PCR分析表明， MdMBL具有组织特异性，在茎中表达量最高，在花中表达量最低；低温胁迫促使MdMBL表达量升高，MdMBL在机械损伤处理下表达量先升高后降低；外源SA能够诱导MdMBL表达上调。%Mannose-binding Lectin(MBL),which belongs to B_LECTIN gene families,was isolated from the young leaf of apple ( Malus domestica) by homologous cloning technology ,named as MdMBL.The cDNA was 1 181 bp in length with an 5′non-coding region of 20 bp,an 3′non-coding region of 81 bp and an open reading frame ( ORF) of 1 080 bp encoding a protein of 359 amino acids ,and the estimated molecular weight and isoelectric point (pI)of the putative protein were 39.76 kDa and 8.72,respectively.The phylogenetic tree of MBL showed that Md-MBL was closest with grapes MBL ,followed by glycine max ,and the evolutionary relationships of homologous genes in apple MdMBL2 was farthest .Quantitative real-time PCR analysis shows that the gene is tissue-specific and ex-pressed highest in stems , the lowest in flowers;The expression of MdMBL was promoted increased with the cold stress and the mechanical damage stress;Exogenous SA could induce up-regulation of MdMBL expression .
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