Abstract
Heat shock proteins (Hsps) are common molecular chaperones present in all plants that accumulate in response to abiotic stress. Small heat shock proteins (sHsps) play important roles in alleviating diverse abiotic stresses, especially heat stress. However, very little is known about the MsHsp20 gene family in the wild apple Malus sieversii, a precious germplasm resource with excellent resistance characteristics. In this study, 12 putative M. sieversii Hsp20 genes were identified from RNA-Seq data and analyzed in terms of gene structure and phylogenetic relationships. A new Hsp20 gene, MsHsp16.9, was cloned and its function studied in response to stress. MsHsp16.9 expression was strongly induced by heat, and transgenic Arabidopsis plants overexpressing MsHsp16.9 displayed improved heat resistance, enhanced antioxidant enzyme activity, and decreased peroxide content. Overexpression of MsHsp16.9 did not alter the growth or development under normal conditions, or the hypersensitivity to exogenous ABA. Gene expression analysis indicated that MsHsp16.9 mainly modulates the expression of proteins involved in antioxidant enzyme synthesis, as well as ABA-independent stress signaling in 35S:MsHsp16.9-L11. However, MsHsp16.9 could activate ABA-dependent signaling pathways in all transgenic plants. Additionally, MsHsp16.9 may function alongside AtHsp70 to maintain protein homeostasis and protect against cell damage. Our results suggest that MsHsp16.9 is a protein chaperone that positively regulates antioxidant enzyme activity and ABA-dependent and independent signaling pathway to attenuate plant responses to severe stress. Transgenic plants exhibited luxuriant growth in high temperature environments.
Highlights
Extreme environments can induce complex biotic and abiotic stress in plants (Cramer et al, 2011)
A total of 2728 differential expression genes (DEG) were identified via clustering analysis (Figure 1) and divided into 25 groups according to the COG classification (Figure 2)
To explain the phenotypic characteristic of the MsHsp16.9 transgenic plants under heat stress and have an insight into the molecular mechanisms of MsHsp16.9-mediated regulation of the heat stress response, we focused on heat stressrelated genes that are differentially expressed between with untransformed control plants (WT) and MsHsp16.9 transgenic plants
Summary
Extreme environments can induce complex biotic and abiotic stress in plants (Cramer et al, 2011). Heat shock proteins (Hsps) are molecular chaperones that stabilize protein structure and protect the cytoplasmic membrane by mediating the folding, assembly, translocation and degradation of proteins and redundant polypeptides in a normal cellular environment (Zhang et al, 2013). These proteins maintain cellular metabolic processes and facilitate survival in extreme environments. SHsps are induced in all organisms in response to environmental stresses and during various developmental processes (Dafny-Yelin et al, 2008)
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