The present invention discloses a pathogenic gene derived from Xanthomonas campestris, a gene encoding phosphoenolpyruvate synthase. The gene encoding phosphoenolpyruvate synthase of this invention has one of the following nucleotide sequence: 1. a nucleotide sequence of SEQ ID NO:1; 2. a DNA sequence which has more than 80% homology with the nucleotide sequence of SEQ ID NO:1, and encodes a protein which has same function as phosphoenolpyruvate synthase encoded by SEQ ID NO:1. The Open Reading Frame of the DNA of SEQ ID NO:1 is from nucleotide 201 to 2576 in its 5' end. It consists of 2379 nucleotides, the initiation codon TTG of this gene is from nucleotides 201 to 203 in its 5' end, and the termination codon TGA of this gene is from nucleotides 2577 to 2579 in its 5' end.