Overexpression of SpCBL6, a calcineurin B-like protein of Stipa purpurea, enhanced cold tolerance and reduced drought tolerance in transgenic Arabidopsis

The purpose of the present study was to characterize SpCBL6 (GenBank accession number: KT780442) from Stipa purpurea and elucidate the function of this protein in abiotic stress. The full-length cDNA of SpCBL6 was isolated from S. purpurea by rapid amplification of cDNA ends methods. Laser confocal microscopy was used to analyze the subcellular localization of SpCBL6. The constructs of 35S:GFP-SpCBL6 was used to transform wild-type (WT) Arabidopsis plants (ecotype Columbia-0) with the floral dip method. Quantitative reverse-transcription PCR (qRT-PCR), water potential, photosynthetic efficiency (F (v)/F (m)), and ion leakage was performed to investigate the role of SpCBL6 in abiotic stress. The open reading frame of SpCBL6 contains 681 bp nucleotides and encodes a 227-amino acid polypeptide. Phylogenetic analysis indicated that SpCBL6 showed the highest similarity with rice OsCBL6. SpCBL6 transcripts were induced by freezing and drought treatments. Subcellular localization analysis showed that SpCBL6 was located in membrane of protoplast. Overexpression of SpCBL6 in Arabidopsis thaliana demonstrated that the transgenic plants were more tolerant to cold treatment, but less tolerant to drought, compared with the plants. qRT-PCR analysis showed that the drought stress marker genes were inhibited in transgenic plants, whereas the cold stress marker genes were enhanced. Further analysis showed that SpCBL6-overexpressing plants showed enhanced water potential, photosynthetic efficiency (F (v)/F (m)), and reduced ion leakage compared with the wild-type after cold treatment. Collectively, these results indicate that SpCBL6, a new member of the CBL gene family isolated from S. purpurea, enhances cold tolerance and reduces drought tolerance in plants.