[Genetic and molecular characters of toxin producing Erwinia chrysanthemi pv. zeae]

Bacterial foot rot, caused by Erwinia chrysanthemi pv. zeae, is one of the most important diseases in rice. Genetic and molecular characters of toxin producting for Erwinia chrysanthemi pv. zeae were conducted in this paper.

A plasmid-deficient strain, Ech7-mul, was obtained by chemical mutation,and the relative specific molecular mark with toxin was screened from Random Amplified Polymorphic DNA (RAPD) by PCR.

The wild strain Ech7 and the plasmid-deficient strain Ech7-mul could both produce toxin.We screened 260 random primers in PCR, and found that a specific fragment (2139bp) could be amplified with K10 primer from theminus-toxin strain Ech7-4 DNA, but could not from the wild strain Ech7 DNA. The amplified fragment DNA was cloned and sequenced, and specific primers were designed to amplify it. The 2139bp fragment DNA could be a specific molecular mark with 100% SCAR identity between wild strain and the toxin mutant strain. Sequence analysis showed that there were five open reading frame (ORF), two of them were NADH-flavin reductase and N-acetyltransferase,respectively. Another ORF, located in the end region of 2139bp fragment, had 66% and 46% homologies with permeases of the drug/metabolite transporter (DMT) from Pseudomonas aerginosa (ZP00136947) and Yersinia Pestis (ZP01177873).

Toxin biosynthesis in E. chrysanthemi pv. zeae might be coded by chromosome, but not by the bacterial plasmid.The position of gene mutation in the mutant Ech7-4 might be at the 3' region of toxin-relation SCAR DNA fragment.