title: Functional characterization of the Arabidopsis bHLH92 transcription factor in abiotic stress.
abstract: In our previous microarray analysis of NaCl-treated Arabidopsis roots, we identified a basic-helix-loop-helix (bHLH) transcription factor, bHLH92 (At5g43650), as one of the transcripts showing the greatest fold-increase in abundance upon NaCl exposure. Here, we characterize the role of bHLH92 in the context of abiotic stress physiology and hormone responses. We observed that bHLH92 transcript abundance increases in response to NaCl, dehydration, mannitol, and cold treatments, and compared these responses to those of two closely related genes: bHLH41 and bHLH42. The NaCl-inducibility of bHLH92 was only partially dependent on abscisic acid (ABA) biosynthesis and SALT OVERLY SENSITIVE2 (SOS2) pathways. As compared to WT, root elongation of bhlh92 mutants was more sensitive to mannitol, and these mutants also showed increased electrolyte leakage following NaCl treatments. Overexpression of bHLH92 moderately increased the tolerance to NaCl and osmotic stresses. Finally, we identified at least 19 putative downstream target genes of bHLH92 under NaCl treatment using an oligonucleotide microarray. Together these data show that bHLH92 functions in plant responses to osmotic stresses, although the net contribution of bHLH92-regulated genes to stress tolerance appears relatively limited in proportion to what might be expected from its transcript expression pattern.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada.
authors.forename: Yuanqing
authors.initials: Y
authors.lastname: Jiang
authors.forename: Bo
authors.initials: B
authors.lastname: Yang
authors.forename: Michael K
authors.initials: MK
authors.lastname: Deyholos
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D000222:Adaptation, Physiological / Q000187:drug effects / Q000235:genetics; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics* / Q000378:metabolism; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D006861:Hydrogen Peroxide / Q000378:metabolism; D018527:Hydroponics; D016254:Mutagenesis, Insertional / Q000235:genetics; D009154:Mutation / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D009928:Organ Specificity / Q000187:drug effects; D009995:Osmosis / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D012965:Sodium Chloride / Q000494:pharmacology; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D000040:Abscisic Acid; D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D004269:DNA, Bacterial; D006861:Hydrogen Peroxide; D012333:RNA, Messenger; D012965:Sodium Chloride; D014157:Transcription Factors; C036483:T-DNA; C547169:bHLH92 protein, Arabidopsis