PROBLEM TO BE SOLVED: To obtain an aldehyde oxidase gene comprising a gene obtained from a plant and having a specific molecular weight, coding an amino acid sequence of an enzyme having activities capable of forming a carboxylic acid by oxidizing an aldehyde compound and useful for production, etc., of plant growth hormone. SOLUTION: This aldehyde oxidase gene is a gene obtained from a plant and having about 4.4kbp, codes an enzyme having activities capable of forming a carboxylic acid by oxidizing an aldehyde compound and further having an amino acid sequence of the formula, and useful as IAA biosynthesis enzyme, etc., having activities for forming indoleacetic acid(IAA) of plant growing hormone by oxidizing indoleacetaldehyde and suitable for clarification of synthesis root of IAA of a plant and breeding of the plant. The gene is obtained by sprouting a cone seed, extracting RNA from the tip part of the coleoptile, synthesizing DNA by using the RNA and cloning the DNA by performing a PCR by using a primer.
