Functional characterization of Arabidopsis HsfA6a as a heat‐shock transcription factor under high salinity and dehydration conditions

• Published in: Plant, cell and environment cell and environment, 2014-05, Vol.37 (5), p.1202-1222
• Main Authors: HWANG, SUNG MIN, KIM, DAE WON, WOO, MIN SEOK, JEONG, HYEONG SEOP, SON, YOUNG SIM, AKHTER, SALINA, CHOI, GYUNG JA, BAHK, JEONG DONG
• Format: Article
• Language: English
• Subjects: ABA‐dependent signalling pathway; ABF/AREB proteins; abscisic acid; abscisic acid (ABA); Abscisic Acid - pharmacology; Adaptation, Physiological - drug effects; Adaptation, Physiological - genetics; Arabidopsis - drug effects; Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis - physiology; Arabidopsis Proteins - chemistry; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; AtHsfA6a; binding proteins; Biological and medical sciences; Cell Nucleus - drug effects; Cell Nucleus - metabolism; cold; cytoplasm; Dehydration; DNA, Bacterial - genetics; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; drought; Droughts; electrophoresis; fractionation; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant - drug effects; gene overexpression; genes; heat; Heat Shock Transcription Factors; microarray technology; Mutagenesis, Insertional - genetics; Promoter Regions, Genetic - genetics; Protein Binding - drug effects; Protein Binding - genetics; Reproducibility of Results; reverse transcriptase polymerase chain reaction; Saccharomyces cerevisiae - cytology; Salinity; seed germination; seedlings; Signal Transduction - drug effects; Signal Transduction - genetics; sodium chloride; Subcellular Fractions - drug effects; Subcellular Fractions - metabolism; transcription (genetics); transcription factors; Transcription Factors - chemistry; Transcription Factors - genetics; Transcription Factors - metabolism; transcriptional activation; Transcriptional Activation - drug effects; Transcriptional Activation - genetics; transcriptional activator; Up-Regulation - drug effects; Up-Regulation - genetics
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.12228

Although heat‐shock transcription factors are well characterized in the heat stress‐related pathway, they are poorly understood in other stress responses. Here, we functionally characterized AtHsfA6a in the presence of exogenous abscisic acid (ABA) and under high salinity and dehydration conditions. AtHsfA6a expression under normal conditions is very low, but was highly induced by exogenous ABA, NaCl and drought. Unexpectedly, the levels of AtHsfA6a transcript were not significantly altered under heat and cold stresses. Electrophoretic mobility shift assays and transient transactivation assays indicated that AtHsfA6a is transcriptionally regulated by ABA‐responsive element binding factor/ABA‐responsive element binding protein, which are key regulators of the ABA signalling pathway. Additionally, fractionation and protoplast transient assays showed that AtHsfA6a was in cytoplasm and nucleus simultaneously; however, under conditions of high salinity the majority of AtHsfA6A was in the nucleus. Furthermore, at both seed germination and seedlings stage, plants overexpressing AtHsfA6a were hypersensitive to ABA and exhibited enhanced tolerance against salt and drought stresses. Finally, the microarray and qRT‐PCR analyses revealed that many stress‐responsive genes were up‐regulated in the plants overexpressing AtHsfA6a. Taken together, the data strongly suggest that AtHsfA6a acts as a transcriptional activator of stress‐responsive genes via the ABA‐dependent signalling pathway.