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Jasmonic acid (JA) is a phytohormone that plays important roles in growth, development, and defense in plants. Although many functions and mechanisms of JA are known, some pathways are still unclear. One of the simplest approaches to understanding JA signal transduction is isolating mutants that respond abnormally to JA. From the defects of such mutants we can determine the regulatory functions of JA. jasmonate hypersensitive 2 (jah2) is a JA hypersensitive mutant. JA normally inhibits the root growth of plants and the jah2 mutant has an even shorter root compared with wild-type Col-0 (wild type) under the same JA concentration. Examination of the sensitivity of jah2 showed that jah2 and WT have a 100-fold JA-sensitivity difference. While jah2 was hypersensitive to JA, it was not hypersensitive to two other hormones, IAA and the precursor of ethylene, ACC. Two types of PCR-based markers (CAPS and SSLP) were used to map jah2. The jah2 mutant (in Col-0) was crossed with Ler to generate recombinants with sequence polymorphisms between the two ecotypes. F2 mutants homozygous for the jah2 phenotype were selected from JA-containing agar media. Initially, bulk segregant analysis was used until a linked marker was found; afterwards individual F2 mutants were tested. The jah2 area was narrowed down to a region of about 177kb on Chromosome 5. Illumina whole genome sequence analysis of jah2 was compared with a reference wild type sequence. The jah2 mutant had two G-A single nucleotide transitions within the mapped area. One was in an intergenic region and the other was in intron six of glutathione synthetase gene (GSH2). This suggests that GSH2 is the mutated gene in jah2, which is consistent with previous findings that JA signaling has some interactions with glutathione and redox signaling in plants.