Abstract:Heat shock transcription factors (Hsfs) widely exist in plants and play a key role under extreme environmental conditions, especially under heat shock stress. Most researches focused on model plants such as Arabidopsis and tomato (Lycopersicon esculentum). There were few reports about maize Hsfs so far. In this study, a Hsf gene, named ZmHsf06 (GenBank accession: GRMZM2G115456_T01), was cloned from maize (Zea mays) young leaves treated by heat shock at 42 ℃ for 1 h using homologous cloning methods. The patterns of ZmHsf06 expression level in different organs and its subcellular location were analyzed. Sequence analysis showed that the coding sequences (CDS) of ZmHsf06 was 1 584 bp encoding a protein of 527 amino acids. ZmHsf06 contained not only the most conserved and typical DNA-binding domain (DBD) of Hsf family, but also other functional domains such as a nuclear localization signal (NLS) KKRR peptide, a nuclear export signal (NES) IGDLTEQM peptide and an aromatic, large hydrophobic and acidic amino residues (AHA) DSFWEQFL peptide. Real-time quantitative PCR (qRT-PCR) analysis showed that under normal growth conditions, ZmHsf06 expressed in roots, stems and leaves of maize seedlings with the highest expression level in roots, and also in functional leaves, ears, immature embryo and pollen at anther period with the highest expression level in pollen and the lowest in leaves. The expression level of ZmHsf06 was up-regulated by 42 ℃ heat shock, abscisic acid(ABA) and salt stress, respectively. In details, under heat shock of 42 ℃, the highest expression level of ZmHsf06 in roots was 16 folds of that in leaves, and it appeared later than in leaves. While treated with ABA, the highest expression level in leaves was 2 folds of that in roots, and it appeared later than in roots. Under salt stress, the expression levels of ZmHsf06 in leaves and roots were increased significantly and shared the similar patterns. Based on transient expression assay using onion (Allium cepa L.) epidermis, it was found that the ZmHsf06 was located in nucleus specifically both under normal condition and heat shock at 37 ℃ within 1 h. It suggested that ZmHsf06 probably participates in signal transduction process of pollen development and responses to abiotic stresses at transcription level, and functions in nucleus. The results of this work provide basic data for isolating and characterizing more Hsfs in maize, as well as exploring their biological functions in abiotic stresses.
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