早熟砂梨‘翠冠’hmgr基因家族两成员的表达与货架期黑皮病关系的研究

 以砂梨黑皮病易感品种‘翠冠’果实为材料，克隆获得了调控α-法尼烯合成的关键限速酶3-羟基-3-甲基戊二酸单酰辅酶A还原酶（HMGR）基因家族中的两个成员Pphmgr1和Pphmgr2。Pphmgr1开放阅读框为1 827 bp，编码由609个氨基酸残基组成的蛋白；Pphmgr2开放阅读框为1 707 bp，编码由569个氨基酸残基组成的蛋白。序列比对结果显示：‘翠冠’PpHMGR1和PpHMGR2与苹果果实的MdHMGR1和MdHMGR2蛋白的同源性分别达到90%和98%。在采后货架期28~32 ℃条件下，乙烯受体抑制剂1-MCP 可明显抑制果实呼吸率，减缓乙烯释放，显著降低果皮中α-法尼烯及其氧化产物共轭三烯的含量，减少黑皮病发病率并减轻发病程度。半定量RT-PCR结果显示1-MCP处理后果皮中Pphmgr2的表达受到显著抑制，但是Pphmgr1的表达几乎不受影响。

The Relationship Between Expression Patterns of Two Members of hmgr Gene Family and Superficial Scald in Eearly Maturity Sandy Pear 'Cuiguan' During Shelf Life

In this study, Pphmgr1 and Pphmgr2, two members of hmgr gene family which encodes α-farnesene metabolism rate-limiting enzyme HMGR were cloned from scald-susceptible sandy pear variety 'Cuiguan' peel, respectively. Pphmgr1 cDNA has an open reading frame of 1 827 nucleotides and encodes a polypeptide including 609 residues which relative molecular mass was 64.80 kD; while Pphmgr2 cDNA has an opening reading frame of 1 707 nucleotides and encodes a polypeptide including 569 residues which relative molecular mass was 60.21 kD. The deduced amino acid sequences were from Pphmgr1 and Pphmgr2 showed 90% and 98% homology with apple MdHMGR1 and MdHMGR2, respectively. Under high temperature shelf life condition (28~32 ℃), ethylene receptor inhibitor 1-MCP significantly decreased respiration rate and alleviated ethylene production rate. At the same time, α-farnesene and conjugated trienols contents were significantly decreased and occurring times of their peak values were postponed together. The semi-quantitative RT-PCR results showed that Pphmgr1 was constitutively expression, while expression of Pphmgr2 was inhibited by 1-MCP obviously. The results showed that under the experiment temperature conditions (28-32 ℃) 1-MCP inhibited ethylene metabolism and respiration rate so as to decrease the expression abundance of Pphmgr2, which probably directly led to the depression of α-farnesene synthetic metabolism and thus to reduce the superficial scald incidence of 'Cuiguan' pear after harvest at last.