Abstract
Sedum alfredii 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 Hsf gene family in S. alfredii based on a transcriptome under Cd stress. There were 22 Hsf 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 Hsf members showed significant differences: 18 SaHsfs were responsive to Cd stress, as were multiple SaHsp genes, including SaHsp18.1, SaHsp22, SaHsp26.5, SaHsp70, SaHsp90, and SaHsp101. Two class A4 members, SaHsfA4a and SaHsfA4c, exhibited transcriptional activation activities. Overexpression of SaHsfA4a and SaHsfA4c in transgenic yeast indicated an improved tolerance to Cd stress and Cd accumulation. Our results suggest SaHsfs 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 SaHsfs.
Highlights
Abiotic stresses, such as heavy metal, heat, cold, drought, and salinity, adversely affect the growth and development of plants
A comprehensive analysis of the heat shock transcription factor (Hsf) family was performed, including phylogenetic, conserved domain, and motif analyses and expression profiling, under Cd stress based on transcriptome sequencing
A total of 22 Hsf members were identified from S. alfredii using bioinformatics
Summary
Abiotic stresses, such as heavy metal, heat, cold, drought, and salinity, adversely affect the growth and development of plants. They have had to develop defenses or adaptation mechanisms to deal with various stresses present during evolution [1,2,3,4] These mechanisms can be processed including multiple genes and signaling pathways, which produce a series of physiological and biochemical changes in order to resist stress damage [5,6,7]. Each stage of these processes involves different types of transcription factors and cis-acting elements in stress-responsive promoters, which are controlled by different signal conditioning mechanisms in order to enable plant adaptation to environmental stresses [8]. Among these important transcription factors, heat shock transcription factors (Hsfs) are well known for responding to external high-temperature stress and activating the expression of heat shock proteins (Hsps) by combining with the heat shock element (HSE)
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