Isolation of nine Phytophthora capsici pectin methylesterase genes which are differentially expressed in various plant species

Abstract

Phytophthora capsici causes damage on many plants species, and secretes various pectin methylesterases during all stages of infection. We identified nine Pme genes (Pcpme 1-9) from a genomic library of highly virulent P. capsici strain SD33 and further analyzed the expression pattern of nine genes on three hosts: pepper, tomato, and cucumber using qRT-PCR during all stages of infection. All nine genes were found to be differentially expressed in three host species in the course of P. capsici interaction. The expression levels of the respective genes increased from 1 to 7 dpi in pepper, while most genes presented a decreasing trend of expression from 1 to 5 dpi in tomato fruits. However, in both fruits peaks were reached at 7 dpi. In cucumber fruits, each gene showed minor expression levels from 1 to 3 dpi, exhibited definite peaks at 5 dpi, and then decreased from 5 to 7 dpi. Thus, evidence from our studies of Pcpme gene expression in different plants at a rang of time points suggests that the late stages of infection may represent the most critical time for P. capsici to successfully express or/and secret PMEs.