Identification, Expression Analysis of the Hsf Family, and Characterization of Class A4 in Hance under Cadmium Stress.

Hance, a cadmium (Cd)/zinc (Zn)/lead (Pb) co-hyperaccumulating species, is a promising phytoremediation candidate because it accumulates substantial amounts of heavy metal ions without showing any obvious signs of poisoning. The heat shock transcription factor (Hsf) family plays crucial roles in plant growth, development, and stress responses. Although the roles of some Hsfs in abiotic stress have been well studied in model plants, the Hsf family has not been systematically investigated in heavy metal hyperaccumulators. Here, we comprehensively analyzed the gene family in based on a transcriptome under Cd stress. There were 22 members that were identified and phylogenetically clustered into three classes, namely, SaHsfA, SaHsfB, and SaHsfC. All of the three classes shared similar motifs. The expression profiles of the 22 members showed significant differences: 18 were responsive to Cd stress, as were multiple genes, including , , , , and . Two class A4 members, and , exhibited transcriptional activation activities. Overexpression of and in transgenic yeast indicated an improved tolerance to Cd stress and Cd accumulation. Our results suggest play important regulatory roles in heavy metal stress responses, and provide a reference for further studies on the mechanism of heavy metal stress regulation by .