Cloning and functional analysis of heat shock protein SpHSP70-3 gene from Sorbus pohuashanensis

  Objective  This paper aims to explore the function of heat shock protein (HSP) in Sorbus pohuashanensis in response to high temperature stress, and to provide theoretical basis for the introduction of species in low altitude areas.

  Method  Taking 2−4 years old seedlings of Sorbus pohuashanensis as the research object, the cloning, phylogenetic analysis, tissue-specific expression pattern and expression mechanism in response to high temperature stress of Sorbus pohuashanensis were studied, and the response function of transgenic Arabidopsis thaliana to high temperature stress was verified by agrobacterium-mediated transformation.

  Result  The full-length open reading frame of SpHSP70-3 gene was 2 088 bp, encoding 695 amino acids. SpHSP70-3 protein had the highest homology with Pyrus bretschneideri PbHSP70 in Rosaceae. Endogenous expression analysis showed that the expression of SpHSP70-3 gene was the highest in leaves, but the expression was low in bud, first flower and full flower. The expression level did not change significantly 6 h before treatment at 42 ℃, but increased to 12 times of the control group at 12 h, and reached the highest level at 24 h, but only 19 times of the control group. After three homozygous arabidopsis lines of OE1, OE2 and OE3 with SpHSP70-3 gene and WT arabidopsis were treated at 45 ℃, the MDA contents in OE1, OE2 and OE3 were all higher than WT, and the CAT enzyme activity and POD enzyme activity were lower than WT. In addition, the expression of SpHSP70-3 in transgenic lines increased with the increase of treatment time, and inhibited the expression of positive regulatory factors AtHSP70, AtHSP18.2, AtHsfA1D and AtHsfA1A, while induced the up-regulation of negative regulatory factor AtHsfB2B.

  Conclusion  SpHSP70-3 plays a negative regulatory role in the response of Sorbus pohuashanensis to high temperature stress, and preliminarily speculates that SpHSP70-3 is a negative regulatory factor in the response mechanism of Sorbus pohuashanensis to high temperature stress at low altitude.