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衰老相关蛋白(senescence-associated protein,SSA)基因在果实成熟衰老中起重要作用。为了探究番木瓜衰老相关蛋白基因,以‘大白八号’番木瓜果实为材料,采用RACE技术扩增出番木瓜SSA基因全长cDNA序列,命名为CpSSA(登录号:KX885408)。生物信息学分析显示,CpSSA全长1 203 bp,包含一个420 bp的开放性阅读框。番木瓜SSA蛋白含有139个氨基酸,分子质量为15.172 4 kD,等电点为9.61。该蛋白的氨基酸序列与桃、葡萄、杨树、菠菜的氨基酸序列有较高的同源性。系统进化树显示,番木瓜SSA与葡萄SSA表现出最小的进化距离,亲缘关系最接近。用荧光定量PCR分析在不同处理不同成熟度番木瓜果实中CpSSA基因的表达差异,结果显示在乙烯处理后的6 h和12 h表达量显著升高,在1-MCP处理中表达量较低,在乙烯/1-MCP处理果实中的表达模式与成熟衰老有一定相关性,推测CpSSA基因可能参与了番木瓜果实的成熟衰老进程。
The senescence-associated protein (SSA) gene plays an important role in the fruit ripening and senescence. In order to explore the gene of papaya aging-related proteins, the full-length cDNA sequence of papaya SSA gene was amplified by RACE with the ’Da Bai No.8’ papaya fruit and named CpSSA (accession number: KX885408). Bioinformatics analysis showed that CpSSA was 1 203 bp in length and contained a 420 bp open reading frame. Papaya SSA protein contains 139 amino acids with a molecular mass of 15.172 4 kD and an isoelectric point of 9.61. The amino acid sequence of the protein has high homology with the amino acid sequence of peach, grape, poplar and spinach. Phylogenetic tree showed that papaya SSA and grape SSA showed the smallest evolutionary distance, the closest genetic relationship. The results of quantitative PCR showed that the expression of CpSSA gene in different mature papaya fruits at different maturation stages was significantly increased at 6 h and 12 h after ethylene treatment and lower at 1-MCP treatment. The expression pattern of ethylene / 1-MCP in fruit is related to mature senescence. It is speculated that CpSSA gene may be involved in the process of ripening and senescence of papaya fruit.