翠冠梨PG基因家族两成员的克隆及其表达与货架期果实软化的关系  

Cloning two members of PG gene family from precocious sandy pear Cuiguan and the relationship between their expression and fruit softening during shelf life

作　　者：李慧[1,2] 丛郁[3] 常有宏[1,2] 蔺经[1] 盛宝龙[1] 

机构地区：[1]江苏省农业科学院园艺研究所,南京210014 [2]国家农业科技华东(江苏)创新中心.高效园艺作物遗传改良实验室,南京210014 [3]中国科学院南京土壤研究所土壤与农业可持续发展国家重点实验室,南京210008

出　　处：《果树学报》2012年第1期17-23,共7页Journal of Fruit Science

基　　金：948项目(2009-Z18)

摘　　要：以早熟砂梨翠冠果实为材料,克隆了多聚半乳糖醛酸酶(PG)基因家族中的两成员PpPG1和PpPG2。PpPG1cDNA序列全长1 793 bp,开放阅读框为287～1 666 bp,DNA序列长2 757 bp,包括8个外显子和7个内含子,编码一个含有459个氨基酸残基的蛋白,预测的等电点(pI)为8.47,估计的相对分子质量为49.45 ku。而PpPG2 cDNA序列全长1 671 bp,开放阅读框为120～1 316 bp,DNA序列长2 566 bp,包括3个外显子和2个内含子,编码一个含有398个氨基酸残基的蛋白,预测的等电点(pI)为7.34,估计的相对分子质量为41.14 ku。PpPG1和PpPG2都含有糖苷水解酶Glyco_hydro_28亚家族和多聚半乳糖醛酸酶保守域,它们分别位于系统进化树的两个不同发育分枝上。在夏季货架期,PpPG1和PpPG2基因的表达丰度先上升,PpPG1在采后16 d表达量达到峰值,PpPG2在采后8 d达到峰值,然后均下降;施加1-MCP处理后,PpPG1的表达不受影响,采后8 d的表达丰度下降,PpPG2的表达峰值延后,到采后16 d才达到表达高峰。与此同时,果实PG活性上升速度减缓,乙烯释放速率下降,硬度下降速度减缓。上述结果表明,PpPG1与PpPG2为多聚半乳糖醛酸酶基因家族的不同成员,它们的表达均受乙烯调控,并且PpPG1和PpPG2都与翠冠梨在货架期的果实软化相关。PpPG1 and PpPG2, two numbers of the polygalacturonase gene family were cloned from preco- cious sandy pear Cuiguan （Pyrus pyrifolia Nakai.） fruit by RT-PCR and RACE methods. The results showed that PpPG1 cDNA sequence length is 1 793 bp, which has an open reading frame from 287 to 1 666 nucleotides and encodes a polypeptide including 459 residues. At the same time, PpPG1 DNA se- quence consists of eight exons and seven introns. Predicted isoelectric point （pI） and relative molecular mass of PpPG1 protein were 8.47 and 49.45 ku, respectively. PpPG2 cDNA sequence length is 1 671 bp, which has an open reading frame from 120 to 1 316 nucleotides and encodes a polypeptide including 398 residues. At the same time, PpPG2 DNA sequence consists of three exons and two introns. Predicted iso- electric point （pI） and relative molecular mass of PpPG2 protein were 7.34 and 41.14 ku, respectively. Both PpEG1 and PpEG2 had glucoside hydrolase glyco-hydro-28 superfamily and polygalacturonase conserved domains. The phylogenetic tree analysis showed that PpPG1 and PpPG2 located at two different clades. The semi-quantitative RT-PCR results showed that both PpPG1 and PpPG2 gene expression abun- dance increased and then decreased during summer shelf life （28 to 32 ~C ）. Their expression peaks ap- peared at 16 and 8 days after harvest, respectively. After 1-MCP treatment, PpPG1 expression at postharvest 8 days was inhibited but its expression pattern was not affected. However, PpPG2 expression peak was delayed to postharvest 16 days but its expression abundant was not changed. The fruit characteristics changed after 1-MCP treatment, such as polygalacturonase activity increase speed alleviated, ethylene re- lease rate decreased and fruit firmness decline speed slowed down. It was concluded that PpPG1 and PpPG2 were different numbers of polygalacturonase gene family and their expressions were regulated by ethylene. Both of them played roles in Cuiguan fruit softening during summer shelf life （28 to 32℃ ）.

关 键 词：砂梨 多聚半乳糖醛酸酶 基因克隆 序列分析 表达特点 

分 类 号：S661.2[农业科学—果树学]