[Cloning of GmHSFA1 gene and its overexpression leading to enhancement of heat tolerance in transgenic soybean]

Abstract

Heat shock transcription factors (HSFs) are important in regulating heat stress response by mediating expression of heat shock protein (HSP) genes in various plant species. In the present study, a novel GmHSFA1 with an ORF of 1,533 bp (full-length cDNA sequence of 1,781 bp) was cloned from soybean genome via comparative genomic approach and RACE (rapid amplification of cDNA ends). This gene encodes 510 amino acids consisting of a protein of 56.2 kDa (GenBank accession number: AY458843). Similar to other HSFs, GmHSFA1 has the basic modular structure including DBD, OD, NLS, and CTAD. BLAST analysis revealed the identity of 52.46% between amino acid sequences between GmHSFA1 and LpHSFA1 that has the highest similarity to GmHSFA1 in all HSFA1s in various plant species. The results from RT-PCR, Northern blotting, and transformation showed: 1) GmHsfA1 exhibited the constitutive expression patterns in different tissues of soybean; 2) The expression level of GmHsfA1 in transgenic plants was notably higher than that in non-transgenic plants; 3) Overexpression of GmHsfA1 activated transcription of GmHSP22 in transgenic plants under normal conditions and enhanced obviously expressions of GmHSP23 and GmHSP70 in transgenic plants under heat stress conditions; 4) Heat tolerant temperature (as high as 52 degrees C) of transgenic plants was remarkably higher than that of non-transgenic plants. These results preliminarily proved that the overexpression of GmHsfA1 possibly led to the notable enhancement of heat-tolerant level of transgenic plants by mediating the activation of transcription or improvement of expression of some GmHSPs in the GmHsfA1's downstream in transgenic plants, suggesting GmHSFA1 is a novel and functional heat shock transcription factor of soybean.