Genome-wide identification, phylogenetic and expression analysis of the heat shock transcription factor family in bread wheat (Triticum aestivum L.).

BACKGROUND: Environmental toxicity from non-essential heavy metals such as cadmium (Cd), which is released from human activities and other environmental causes, is rapidly increasing. Wheat can accumulate high levels of Cd in edible tissues, which poses a major hazard to human health. It has been reported that heat shock transcription factor A 4a (HsfA4a) of wheat and rice conferred Cd tolerance by upregulating metallothionein gene expression. However, genome-wide identification, classification, and comparative analysis of the Hsf family in wheat is lacking. Further, because of the promising role of Hsf genes in Cd tolerance, there is need for an understanding of the expression of this family and their functions on wheat under Cd stress. Therefore, here we identify the wheat TaHsf family and to begin to understand the molecular mechanisms mediated by the Hsf family under Cd stress. RESULTS: We first identified 78 putative Hsf homologs using the latest available wheat genome information, of which 38 belonged to class A, 16 to class B and 24 to class C subfamily. Then, we determined chromosome localizations, gene structures, conserved protein motifs, and phylogenetic relationships of these TaHsfs. Using RNA sequencing data over the course of development, we surveyed expression profiles of these TaHsfs during development and under different abiotic stresses to characterise the regulatory network of this family. Finally, we selected 13 TaHsf genes for expression level verification under Cd stress using qRT-PCR. CONCLUSIONS: To our knowledge, this is the first report of the genome organization, evolutionary features and expression profiles of the wheat Hsf gene family. This work therefore lays the foundation for targeted functional analysis of wheat Hsf genes, and contributes to a better understanding of the roles and regulatory mechanism of wheat Hsfs under Cd stress.

Comparative analysis of root transcriptome profiles between low- and high-cadmium-accumulating genotypes of wheat in response to cadmium stress.

Wheat, one of the most broadly cultivated and consumed food crops worldwide, can accumulate high Cd contents in their edible parts, which poses a major hazard to human health. Cd accumulation ability differs among varieties in wheat, but the underlying molecular mechanism is largely unknown. Here, key genes responsible for Cd accumulation between two contrasting wheat genotypes (low-Cd accumulation one L17, high-Cd accumulation one H17) were investigated. Total 1269 were differentially expressed genes (DEGs) in L17 after Cd treatment, whereas, 399 Cd-induced DEGs were found in H17. GO-GO network analysis showed that heme binding was the most active GO, and metal binding was the second one that associated with other GOs in response to Cd stress in both genotypes. Pathway-pathway network analysis showed that phenylpronanoid biosynthesis and glutathione metabolism were the top pathways in response to Cd stress in both genotypes. Furthermore, we found that DEGs related to ion binding, antioxidant defense mechanisms, sulfotransferase activity, and cysteine biosynthetic process were more enriched in L17. In conclusion, our results not only provide the foundation for further exploring the molecular mechanism of Cd accumulation in wheat but also supply new strategies for improving phytoremediation ability of wheat by genetic engineering.