KiwiPME1 encoding pectin methylesterase is specifically expressed in the pollen of a dioecious plant species, kiwifruit (Actinidia chinensis)

摘要

Pectin methylesterases (PMEs) mediate demethylesterification of pectic polysaccharides such as homogalacturonan, a major component of the primary plant cell wall, in the apoplasm. The PMEs are implicated in a number of developmental processes, including pollen development and pollen tube growth, through the fine tuning of the methylesterification status of pectin. In this study, we isolated a full-length cDNA (KiwiPME1) encoding PME from kiwifruit and characterized its molecular features. Analyses of the primary protein structure and gene structure revealed that KiwiPME1 encodes a pre-pro-PME protein that is predicted to localize to the outside of the cell and belongs to group 2 (formerly type 1). The KiwiPME1 expression was highly detected in pollen grains of kiwifruit but not in vegetative tissues investigated. Expression pattern analysis of KiwiPME1 among different floral tissues of male and female plants revealed that KiwiPME1 was expressed specifically in the stamens of flower buds in male and female plants, whereas its expression was detected only in the stamens of male plants when the flowers opened. Expression analysis of KiwiPME1 promoter fused to the GUS reporter gene in Arabidopsis displayed a very similar pattern to that in kiwifruit. Our study suggests that the cell wall-localized KiwiPME1 is likely implicated in the pollen development and pollen tube growth of a dioecious species kiwifruit.