Abstract
Heat shock proteins (HSPs) are ubiquitous protective proteins that play crucial roles in plant development and adaptation to stress, and the aim of this study is to characterize the HSP gene in alfalfa. Here we isolated a small heat shock protein gene (MsHSP17.7) from alfalfa by homology-based cloning. MsHSP17.7 contains a 477-bp open reading frame and encodes a protein of 17.70-kDa. The amino acid sequence shares high identity with MtHSP (93.98 %), PsHSP17.1 (83.13 %), GmHSP17.9 (74.10 %) and SlHSP17.6 (79.25 %). Phylogenetic analysis revealed that MsHSP17.7 belongs to the group of cytosolic class II small heat shock proteins (sHSP), and likely localizes to the cytoplasm. Quantitative RT-PCR indicated that MsHSP17.7 was induced by heat shock, high salinity, peroxide and drought stress. Prokaryotic expression indicated that the salt and peroxide tolerance of Escherichia coli was remarkably enhanced. Transgenic Arabidopsis plants overexpressing MsHSP17.7 exhibited increased root length of transgenic Arabidopsis lines under salt stress compared to the wild-type line. The malondialdehyde (MDA) levels in the transgenic lines were significantly lower than in wild-type, although proline levels were similar between transgenic and wild-type lines. MsHSP17.7 was induced by heat shock, high salinity, oxidative stress and drought stress. Overexpression analysis suggests that MsHSP17.7 might play a key role in response to high salinity stress.Electronic supplementary materialThe online version of this article (doi:10.1007/s11033-016-4008-9) contains supplementary material, which is available to authorized users.
Highlights
Plant Heat shock proteins (HSPs) normally participate in responses to drought, heat shock, salinity, heavy metals and peroxide stress [1]
SignalP-4.1 identified no signal peptides in MsHSP17.7 (Supplementary Fig. 2B)
The MsHSP17.7-overexpressing lines did not show significant differences in proline or Strategies employed by higher plants for surviving adverse conditions include behavioral adaptations, morphological changes and physiological regulation [18]
Summary
Plant HSPs normally participate in responses to drought, heat shock, salinity, heavy metals and peroxide stress [1]. HSPs act as molecular chaperones that bind other proteins to maintain steady-state target protein and promote the recovery of denatured proteins, which allows homeostasis of the internal environment during plant development and stress adaptation [2]. SHSPs just bind to misfolded or denatured protein substrates, whereas refolding steps are mediated by Hsp70/ Hsp100 complexes [6], preventing irreversible unfolding or aberrant protein aggregation [7]. Their ability to prevent irreversible protein aggregation and to resolubilize aggregated proteins allows native proteins to remain in a stable state. SHSPs have been described as the ‘paramedics of the cell’ [8, 9]
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