An Acyl–acyl Carrier Protein Thioesterase Gene Isolated from Wintersweet (Chimonanthus praecox), CpFATB, Enhances Drought Tolerance in Transgenic Tobacco (Nicotiana tobaccum)

摘要

In this study, a full-length complementary deoxyribunucleic acid (cDNA) of a fatty acyl–acyl carrier protein thioesterase (CpFATB) was isolated from a Chimonanthus praecox (wintersweet) cDNA library. Wintersweet is a hardy shrub native to Chinese montane regions and is known to be tolerant to many biotic and abiotic stresses including cold, drought, and a variety of plant pathogens. The cDNA is 1,110 nucleotides in length, of which 1,107 bp form a single open-reading frame, predicting a 369 amino acid polypeptide. The deduced amino acid sequence of CpFATB displayed high homology to choroplastic palmitoyl–acyl carrier protein thioesterases from other plants. This gene was subsequently overexpressed in Nicotiana tobaccum using Agrobacterium tumefaciens-mediated transformation. Transcripts of CpFATB were shown to be abundant in leaves of the transformants, but were less highly expressed in roots and least highly expressed in stem tissues. Analysis of the fatty acid composition of transformant leaf tissue showed that the levels of myristic acid (C14:0) in leaf material of transgenic plants was increased by 46% compared with levels observed in wild-type plants. In addition, the level of oleate (C18:1) was reduced by 35%. Of most interest, was the observation that the transformants displayed a far higher degree of drought tolerance than wild type. These data suggest that the CpFATB product may be of utility in the production of transgenic, drought-tolerant crop species.