Abstract
Heat shock factors (Hsfs) are important regulators of stress-response in plants. However, our understanding of Hsf genes and their responses to temperature stresses in two Pooideae cool-season grasses, Festuca arundinacea, and Lolium perenne, is limited. Here we conducted comparative transcriptome analyses of plant leaves exposed to heat or cold stress for 10 h. Approximately, 30% and 25% of the genes expressed in the two species showed significant changes under heat and cold stress, respectively, including subsets of Hsfs and their target genes. We uncovered 74 Hsfs in F. arundinacea and 52 Hsfs in L. perenne, and categorized these genes into three subfamilies, HsfA, HsfB, and HsfC based on protein sequence homology to known Hsf members in model organisms. The Hsfs showed a strong response to heat and/or cold stress. The expression of HsfAs was elevated under heat stress, especially in class HsfA2, which exhibited the most dramatic responses. HsfBs were upregulated by the both temperature conditions, and HsfCs mainly showed an increase in expression under cold stress. The target genes of Hsfs, such as heat shock protein (HSP), ascorbate peroxidase (APX), inositol-3-phosphate synthase (IPS), and galactinol synthase (GOLS1), showed strong and unique responses to different stressors. We comprehensively detected Hsfs and their target genes in F. arundinacea and L. perenne, providing a foundation for future gene function studies and genetic engineering to improve stress tolerance in grasses and other crops.
Highlights
Climate change has resulted in harmful effects on plant growth (Hasanuzzaman et al, 2013; Miura and Furumoto, 2013)
The coding region sequences (CDS) sequences were aligned to protein databases in the priority order of NR, Swiss-Prot, KEGG, and Cluster of Orthologous Groups of proteins (COG); this resulted in 56,141 unigenes, with 6258 sequences that did not align to any database
heat stress (HS) resulted in more differentially expressed genes (DEGs) than that observed under cold stress (CS), and less overlap was detected under the two temperature conditions
Summary
Climate change has resulted in harmful effects on plant growth (Hasanuzzaman et al, 2013; Miura and Furumoto, 2013). Hsfs of Tall Fescue and Perennial Ryegrass below −10◦C in the winter almost every year, which greatly exceeds the growth temperature of these cool-season grasses, and reduces the forage yield and lawn quality. Improving tall fescue and perennial ryegrass adaptability to high and/or low temperature can increase forage yield and lawn quality in regions where it is heavily planted. Plants cope with adverse environmental changes by altering expression of stress-related genes (Krasensky and Jonak, 2012). Heat shock proteins (HSPs), which include HSP70 (DnaK), the chaperonins (GroEL and HSP60), HSP90, HSP100 (Clp), and the small HSP (sHSP) families (Wang et al, 2004), are important molecular chaperones, and their expression is induced by environmental stressors such as heat, waterlog, salinity, osmosis, cold, and oxidation (Timperio et al, 2008; Scharf et al, 2012; Hu et al, 2015). HSPs prevent aggregation of denatured proteins, and assist in folding of nascent polypeptides and refolding denatured proteins, as well as to re-solubilize aggregated denatured proteins (Wang et al, 2004; Timperio et al, 2008; Waters, 2013)
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