桃果胶裂解酶编码基因PpPL1的鉴定及其在果实成熟软化过程中的表达

为了深入了解桃果胶裂解酶(PL)家族编码基因的功能,本研究利用生物信息学方法对桃基因组中的PL基因进行鉴定,并对这些基因在硬质型桃和溶质型桃果实成熟软化过程中的表达差异进行分析。结果表明,从桃基因组中共鉴定出20个PL基因,所有的PpPL蛋白都含有Pec-Lyase-C结构域,但其中只有4个PpPL(PpPL7、PpPL8、PpPL12、PpPL17)包含Pec-Lyase-N结构域。Pec-Lyase-N的保守性表明其可能是执行果胶裂解功能所必须的功能团。聚类分析表明,桃PL基因可以分为5类:这与模式植物拟南芥和番茄PL基因的聚类模式一致。基因表达分析表明,6个PL基因在桃果实成熟过程中高表达,其中PpPL1基因在有名硬质型桃成熟过程中表达量很低,而在黄金蜜3号溶质型桃成熟阶段高表达。序列比对和聚类分析发现,PpPL1基因与果实软化相关的番茄SLPL高度同源。以溶质型桃湖景蜜露和硬质型桃夏之梦为试材,检测采后软化过程中PpPL1的表达,结果表明PpPL1基因是与桃果实的成熟软化相关的主要基因。本研究结果为进一步探究PL基因家族在桃果实软化中作用的分子机理奠定了基础。

Identification of Peach Pectate lyase Coding Gene PpPL1 and Its Expression During Fruit Ripening and Softening

To clarify the function of pectate lyases in peaches, we identified all PL genes in the peach genome by using bioinformatics analysis; moreover, we analyzed the differential expression of these genes during the ripening and softening of melting flesh and stony hard peaches. The analysis revealed 20 PpPL candidate genes in the peach genome. All PpPL proteins contained the Pec-lyase-C domain, but only 4 PpPL proteins (PpPL7, PpPL8, PpPL12, and PpPL17) contained the Pec-lyase-N domain. That indicate that Pec-lyase-C of PL may be the necessary functional domain for pectin cleavage. Phylogenetic analysis revealed that these PpPL family genes could be divided into 5 groups: types Ⅰ~Ⅴ. Expression analysis showed that 6 PL genes were highly expressed during fruit ripening, and the expression of PpPL1 in melting flesh peaches (Yumyeong) was considerably higher than that in stony hard peaches (Golden Honey 3). Through sequence alignment and cluster analysis, we observed that PpPL1 and tomato softening-related SLPL were highly homologous. Using melting flesh peaches (Hujing Milu) and stony hard peaches (Xia Zhimeng) as test materials, we observed that PpPL1 exhibited higher expression during postharvest storage of Hujingmilu. These results suggest that PpPL1 is a candidate gene involved in peach softening. This study thus provides a foundation for further exploration of the molecular mechanism of PL genes in peach fruit softening.