Cloning and Characterization of an Annexin Gene from Cynanchum komarovii that Enhances Tolerance to Drought and Fusarium oxysporum in Transgenic Cotton

A novel plant annexin, CkANN, was isolated from Cynanchum komarovii. Sequence analysis showed that CkANN contained four conserved exdonexin fold regions, a putative peroxidase heme binding motif and two S3 clusters. Real-time PCR analysis indicated that the CkANN mRNA was abundant in leaf, flower, root and stem and that its level is highest in leaf and flower. The transcription level of CkANN was increased significantly following stress by salicylic acid (SA), methyl jasmonate (MeJA), abscisic acid (ABA), NaCl, PEG 6000 (polyethylene glycol) and H(2)O(2). Over-expression of CkANN in transgenic cotton caused a significant increase in tolerance to drought and led to higher levels of proline and soluble carbohydrates compared to wild-type (WT) plants. In response to drought, the transgenic plants also displayed higher total chlorophyll levels and reduced accumulation of thiobarbituric acid-reactive substances (TBARS) compared to WT plants. Furthermore, the transgenic cotton showed enhanced resistance to Fusarium oxysporum via increased total peroxidase activity and induction of the expression of some pathogenesis-related proteins. In conclusion, this study has demonstrated that C. komarovii CkANN is involved in drought tolerance and disease resistance and therefore may contribute significantly to the development of drought- or disease-resistant crops.