荔枝果实内切-1,4-β-葡聚糖酶基因(EG)的克隆及其表达分析

Cloning and Expression Analysis of EG Genes in Litchi Fruit

采用RT-PCR和RACE相结合的方法,从荔枝果实中分离得到两个内切-1,4-β-葡聚糖酶基因(EG)全长序列,分别命名为LcEG1和LcEG2。推导的LcEG1和LcEG2蛋白均含有4个半胱氨酸Cys残基和两个保守的糖基水解酶启动位点。Northernblotting分析表明,LcEG1mRNA在果皮发育过程中逐渐减弱,而在果肉发育过程中逐渐增强;LcEG2仅在果肉发育的前期表达,在果皮中检测不到其表达。LcEG1在荔枝易裂果品种‘糯米糍’果皮和果肉中的表达均明显强于在不易裂果品种‘淮枝’果皮和果肉中的表达。上述结果表明,LcEG1的表达可能参与荔枝果实发育,并且与裂果密切相关,而LcEG2可能只参与果肉的早期生长。

Two different full lengths of EG cDNAs, termed as LcEG1 and LcEG2, were isolated from litchi fruit using RT-PCR and RACE （rapid amplification of cDNA ends ） methods. Sequence alignment showed that four typical Cys residues and two predicted glycosyl hydrolase active sites were observed in the deduced LeEG1 and LcEG2 proteins. Northern blotting analysis showed that the level of LcEG1 mRNA accumulation gradually decreased in pericarp but steadily increased in aril accompanying with fruit growth and development, while the expression of LcEG2 could only be detected in aril at early stage of fruit development. More importantly, the accumulation of LcEG1 mRNA was higher in cracking-susceptible cuhivar Nuomici than that in cracking-resistant cultivar Huaizhi at any stage of fruit development. Thus, it could be speculated that LcEG1 was closely related to the growth and cracking of litchi fruit, while, LcEG2 was only related to the growth of fruit at the early phase.