Two CBL genes from Populus euphratica confer multiple stress tolerance in transgenic triploid white poplar

In plants, the calcineurin B-like protein (CBL) family is a unique group of calcium sensors that play a key role in decoding calcium transients by specifically interacting with and regulating a family of CBL-interacting protein kinases. In this study, two CBL genes (PeCBL6 and PeCBL10) from Populus euphratica were isolated by reverse transcription-polymerase chain reaction. To examine their functions, the corresponding cDNAs, which expression was driven by the cauliflower mosaic virus 35S promoter, were cloned into a plant expression vector pCAMBIA1301 and introduced into the triploid white poplar (Popolus tomentosa 'YiXianCiZhu B385'). The physiological parameters, including the percentage of wilted leaves, height growth rate, chlorophyll content, malondialdehyde (MDA) content and relative electrical conductivity (REC) of transgenic lines and wild type (WT) plants, were measured and compared. The results showed that the MDA content and REC of transgenic plants were significantly lower in transgenic plants compared to WT plants when exposed to cold stress and that the presence of the PeCBL gene can induce an increase in height growth rate and a reduction in the number of wilted leaves in comparison to non-transgenic poplars under high salt, drought and cold stress. These results clearly demonstrate that transgenic plants had a greater tolerance to stresses than non-transgenic seedlings, suggesting that PeCBLs might play an important role in stress tolerance.