Correlative evidence for the involvement of phenolic compounds and peroxidase in resistance against Phytophthora colocasiae leaf blight in Colocasia esculenta (taro)

摘要

Peroxidases (PODs) are involved in many plant disease defence responses. Twenty-eight varieties of Colocasia esculenta (taro), with varying degrees of resistance to leaf blight disease caused by Phytophthora colocasiae, were used to assess the possible role of phenolic compounds in resistance to the disease. Total soluble phenolic compound (TSPC) concentrations were negatively correlated with mean lesion diameter (MLD); however, ester-bound phenolic compound (EBPC) concentrations were positively correlated with MLD. Degenerate primers were designed to amplify partial genomic sequences of POD genes, and high-tail PCR was used to clone the flanking sequences from a taro variety that was immune to P. colocasiae with the highest TSPC concentration, in order to obtain a full-length sequence of a taro POD gene. The cloned gene contained the complete open reading frame as well as 5'-upstream and 3'-downstream sequences. It contained four exons, as well as the predicted transcription start site and the poly(A) tail signal. Expression of the taro POD gene (GenBank Accession No. KJ591051) increased more rapidly in an incompatible interaction than in a compatible interaction with P. colocasiae based on real-time quantitative RT-PCR (RT-qPCR).