[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.