Molecular Characterization of a thiJ-like Gene in Chinese Cabbage

Abstract

A cDNA clone for a salicylic acid-induced gene in Chinese cabbage (Brassica rapa subsp. pekinensis) was isolated and characterized. The cabbage gene encoding a protein of 392 amino acids contained a tandem array of two thiJ-like sequences. ThiJ is a thiamin biosynthesis enzyme that catalyzes the phosphorylation of hydroxymethylpyrimidine (HMP) to HMP monophosphate. Although the cabbage gene shows a similarity to bacterial thiJ genes, it also shares a similarity with the human DJ-1, a multifunctional protein that is involved in transcription regulation, male fertility, and parkinsonism. The cabbage thiJ-like gene is strongly induced by salicylic acid and a nonhost pathogen, Pseudomonas syringae pv. tomato, which elicits a hypersensitive response in Chinese cabbage. Treatment of the cabbage leaves with BTH, methyl jasmonate, or ethephon showed that the cabbage thiJ-like gene expression is also strongly induced by BTH, but not by methyl jasmonate or ethylene. This indicates that the cabbage gene is activated via a salicylic acid-dependent signaling pathway. Examination of the tissue-specific expression revealed that the induction of the cabbage gene expression by BTH occurs in the leaf, stem, and floral tissues but not in the root.

The upregulation of thiamine (vitamin B1) biosynthesis in Arabidopsis thaliana seedlings under salt and osmotic stress conditions is mediated by abscisic acid at the early stages of this stress response

“…Our focus on SA was based on previous reports of an activation of a cabbage THIJ -like gene product involved in HMP phosphorylation via the SA-dependent signaling pathway [44] and an involvement of SA in thiamine-induced plant resistance to pathogen attacks [45]. However, our treatments of Arabidopsis plants with exogenous SA did not cause any observable changes in expression of genes involved in thiamine biosynthesis (Figures 5 and 6).…”

Use of cysteine‐reactive cross‐linkers to probe conformational flexibility of human DJ‐1 demonstrates that Glu18 mutations are dimers

“…Furthermore, close plant homologs of human DJ‐1 feature two tandemly repeated DJ‐1 domains that compose a pseudo‐dimeric fusion protein (Oh et al . ). Because such dual DJ‐1 domain fusion proteins cannot dissociate into monomers, they provide strong phylogenetic evidence against the relevance of monomeric DJ‐1, at least in plants.…”

“…However, monomeric DJ-1 is poorly folded and thus not cytoprotective based on prior characterization of monomeric parkinsonism-associated mutants L10P and L166P (Miller et al 2003;Moore et al 2003;Ramsey and Giasson 2010). Furthermore, close plant homologs of human DJ-1 feature two tandemly repeated DJ-1 domains that compose a pseudodimeric fusion protein (Oh et al 2004). Because such dual DJ-1 domain fusion proteins cannot dissociate into monomers, they provide strong phylogenetic evidence against the relevance of monomeric DJ-1, at least in plants.…”

Thiamine and Parkinson's disease

“…Mutations in DJ-1 have been reported to be associated with PD [7,8]. DJ-1 orthologs in a variety of eukaryotic species are similar to the bacterial thiJ gene, which encodes a thiamine biosynthesis enzyme [9,10].…”