Regulation of gibberellin on gene expressions related with the lignin biosynthesis in ‘Wangkumbae’ pear (Pyrus pyrifolia Nakai) fruit

Abstract

‘Wangkumbae’ pear (Pyrus pyrifolia Nakai) was used as material and genes encoding enzymes involved in lignin biosynthesis were cloned: two of 4-coumarate:coenzyme A ligase (4CL) genes Pp4CL1 and Pp4CL2, another two cinnamyl alcohol dehydrogenase (CAD) genes PpCAD1 and PpCAD2, and four peroxidase (POD) genes PpPOD1, PpPOD2, PpPOD3 and PpPOD4. The result of real-time PCR analysis showed a similar expression pattern of PpPAL1 and PpPAL2 with higher accumulation of transcripts at fruit developing early stage and low accumulation at late stage. The expression of PpPAL1 and PpPAL2 revealed down-regulation in gibberellin (GA)-treated fruit. The accumulations of Pp4CL1 and Pp4CL2 transcripts were higher in fruit developing early stage compared with those in late stage, and Pp4CL2 expression level was higher than Pp4CL1. Pp4CL1 and Pp4CL2 expression levels in GA-treated fruit were lower compared with in the control fruit. The relative expression level of PpCAD2 showed higher than PpCAD1 and reached a peak at 53 day after blooming. The expressions of PpCAD2 in GA-treated fruit was significantly lower compared with those in the control fruit in early developmental stage, which was consistent with developmental dynamics of sclereid and dynamic changes in lignin contents during the development. The expression of PpPOD4 gene was significantly higher than PpPOD1, PpPOD2 and PpPOD3 during developmental stages. The expressions of PpPOD1, PpPOD2, and PpPOD4 increased firstly and then decreased during the development of the control fruit. PpPOD1 expression in GA-treated fruit was lower than that in the control fruit, which was consistent with the changes in lignin contents.