Pattern of CsICE1 expression under cold or drought treatment and functional verification through analysis of transgenic Arabidopsis.

CsICE1 is thought to be involved in hardiness resistance of tea plants. Using seedling cuttings of biennial Wuniuzao in this study, the pattern of CsICE1 expression under cold temperature (4°, -5°C), drought [20% polyethylene glycol 6000 (PEG-6000)], and plant hormone [200 mg/L abscisic acid (ABA), 1 mg/L brassinolide (BR)] treatment was studied by real-time quantitative PCR. Additionally, stress resistance, such as the freezing resistance of CsICE1, was studied using Arabidopsis lines transformed with sense or anti-sense CsICE1 via Agrobacterium tumefaciens infection. Our results showed that CsICE1 mRNA could be induced under -5°C, PEG, ABA, or BR treatment, although the pattern of expression differed for all treatments. Compared to wild type (WT) and anti-sense ICE1 transgenic lines, sense lines displayed higher relative germination rates under salt and drought stress. After freezing treatment, the sense transgenic lines over-expressing CsICE1 showed a higher survival rate, increased levels of proline, and decreased levels of malonaldehyde. Conversely, compared with WT, anti-sense ICE1 transgenic lines had lower proline levels and higher malonaldehyde levels under freezing conditions. Our study indicates that CsICE1 is an important anti-freezing gene and that over-expression of CsICE1 can improve cold resistance and enhance salt and drought tolerance of transgenic lines.