猕猴桃AcPAL家族基因的鉴定及在果实成熟过程的表达

Identification of kiwifruit AcPAL family genes and their expression patterns during fruit ripening

关键词:  猕猴桃, 苯丙氨酸解氨酶(PAL), 家族基因特征, 果实成熟, 表达模式

Key words:  kiwifruit(Actinidia chinensis), phenylalanine ammonia-lyase(PAL), family gene characteristics, fruit ripening, expression patterns

摘要:

苯丙氨酸解氨酶(PAL)在植物生长发育和果实成熟中发挥重要作用。为探究猕猴桃AcPAL家族成员特征及其在果实成熟过程中的表达特性,该文从全基因组水平鉴定AcPAL成员并分析不同成员的序列特征、编码蛋白特性、启动子顺式元件、基因结构及系统进化关系,应用实时荧光定量PCR(qRT-PCR)研究它们在不同组织和果实成熟过程中的表达模式。结果表明:(1)共鉴定到7个猕猴桃PAL基因,分别命名为AcPAL1-AcPAL7。AcPAL家族基因编码蛋白含706～722个氨基酸,均为稳定的酸性蛋白。它们具有植物PAL家族的的保守结构域(PLN02457)和活性中心基序(GTITASGDLVPLSYIA)。(2)染色体定位和共线性结果表明,1个串联重复和10次片段重复事件是驱动AcPAL家族成员扩张的主要因素。(3)系统进化树结果表明,AcPAL家族成员均聚在双子叶植物分支,与茶树CsPAL的亲缘关系近。(4)AcPAL家族基因启动子存在多种光响应、胁迫响应、激素响应和生长发育调控元件。(5)qRT-PCR结果表明,不同AcPAL成员在猕猴桃根、茎、叶、花和果实中差异性表达,其中4个成员(AcPAL2、AcPAL3、AcPAL4和AcPAL5)在果实采后成熟阶段显著上调表达,与PAL酶活性的显著升高一致,并受脱落酸(ABA)诱导表达。该研究结果为进一步探究AcPAL在猕猴桃果实采后品质形成中的功能提供了候选基因和理论依据。

Abstract:

Phenylalanine ammonia-lyase(PAL)plays an important role in plant growth and development as well as fruit ripening. To investigate the characteristics of the AcPAL gene family in kiwifruit(Actinidia chinensis)and their expression profiles during fruit ripening, a genome-wide identification of AcPAL genes was performed, followed by analyses of their sequence characteristics, encoded protein properties, promoter cis-acting elements, gene structures, and phylogenetic relationships. Quantitative real-time PCR(qRT-PCR)was employed to detect the expression patterns of these genes in different tissues and during fruit ripening. The results were as follows:(1)A total of seven kiwifruit AcPAL genes were identified and designated as AcPAL1-AcPAL7, respectively. The proteins encoded by the AcPAL family genes consisted of 706-722 amino acids, and all of them were stable acidic proteins. These proteins possess the conserved domain(PLN02457)and active site motif(GTITASGDLVPLSYIA).(2)Chromosomal localization and collinearity analyses revealed that one tandem duplication event and ten segmental duplication events were the major driving forces for the expansion of the AcPAL family members.(3)Phylogenetic tree analysis indicated that all AcPAL family members clustered within the dicotyledon clade and showed a close genetic relationship with CsPAL proteins from Camellia sinensis.(4)The promoters of AcPAL family genes contain a various cis-acting elements involving light response, stress response, hormone response, as well as growth and development regulation.(5)qRT-PCR results showed that different AcPAL members exhibited differential expression patterns in roots, stems, leaves, flowers and fruits of kiwifruit. Notably, four members(AcPAL2, AcPAL3, AcPAL4 and AcPAL5)were significantly up-regulated during postharvest fruit ripening. This expression pattern was consistent with the marked increase in PAL enzyme activity, and their expression was induced by abscisic acid(ABA). These findings provide candidate genes and a theoretical basis for further investigation into the functions of AcPAL genes in the formation of postharvest fruit quality in kiwifruit.