title: Nitric oxide functions as a signal and acts upstream of AtCaM3 in thermotolerance in Arabidopsis seedlings.
abstract: To characterize the role of nitric oxide (NO) in the tolerance of Arabidopsis (Arabidopsis thaliana) to heat shock (HS), we investigated the effects of heat on three types of Arabidopsis seedlings: wild type, noa1(rif1) (for nitric oxide associated1/resistant to inhibition by fosmidomycin1) and nia1nia2 (for nitrate reductase [NR]-defective double mutant), which both exhibit reduced endogenous NO levels, and a rescued line of noa1(rif1). After HS treatment, the survival ratios of the mutant seedlings were lower than those of wild type; however, they were partially restored in the rescued line. Treatment of the seedlings with sodium nitroprusside or S-nitroso-N-acetylpenicillamine revealed that internal NO affects heat sensitivity in a concentration-dependent manner. Calmodulin 3 (CaM3) is a key component of HS signaling in Arabidopsis. Real-time reverse transcription-polymerase chain reaction analysis after HS treatment revealed that the AtCaM3 mRNA level was regulated by the internal NO level. Sodium nitroprusside enhanced the survival of the wild-type and noa1(rif1) seedlings; however, no obvious effects were observed for cam3 single or cam3noa1(rif1) double mutant seedlings, suggesting that AtCaM3 is involved in NO signal transduction as a downstream factor. This point was verified by phenotypic analysis and thermotolerance testing using seedlings of three AtCaM3-overexpressing transgenic lines in an noa1(rif1) background. Electrophoretic mobility-shift and western-blot analyses demonstrated that after HS treatment, NO stimulated the DNA-binding activity of HS transcription factors and the accumulation of heat shock protein 18.2 (HSP18.2) through AtCaM3. These data indicate that NO functions in signaling and acts upstream of AtCaM3 in thermotolerance, which is dependent on increased HS transcription factor DNA-binding activity and HSP accumulation.
authors.affiliation: Hebei Key Laboratory of Molecular and Cellular Biology, School of Life Sciences, Hebei Normal University, Shijiazhuang 050016, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Xuan
authors.forename: Shuo
authors.initials: S
authors.lastname: Zhou
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Yudou
authors.initials: Y
authors.lastname: Cheng
authors.forename: Liqun
authors.initials: L
authors.lastname: Zhao
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002147:Calmodulin / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D000076249:Heat Shock Transcription Factors; D018869:Heat-Shock Response; D006358:Hot Temperature; D009154:Mutation; D009569:Nitric Oxide / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D018749:RNA, Plant / Q000378:metabolism; D036226:Seedlings / Q000502:physiology*; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C541275:CaM3 protein, Arabidopsis; D002147:Calmodulin; D004268:DNA-Binding Proteins; D000076249:Heat Shock Transcription Factors; D012333:RNA, Messenger; D018749:RNA, Plant; D014157:Transcription Factors; D009569:Nitric Oxide