Abstract:

Abiotic stresses such as drought, salinity and low temperature extremely limit crop productivity. However, abiotic stress tolerance is controlled by complex multigene, and many key genes in the transduction networks are still not investigated. Thus, it is important to discover new genes involved in abiotic stress response and/or tolerance. ABC1 subfamily is a member of the Protein kinase family. The exact functions of ABC1are not clear; however results in yeast showed that ABC1 could reduce the mis-translation of a cytochrome b and stable bc1 complex of the electron transport chain in the mitochondria. The abc1/coq8 null mutants led to defective CoQ biosynthesis and respiratory deficiency in yeast. CoQ analogues have been shown to be capable of regulating the mitochondrial permeability transition pore; therefore it was supposed that ABC1/COQ8 might be involved in the regulation of CoQ biosynthesis. Evidence from E. coli indicated that ABC1 acted as a lipid soluble anti-oxidant and required for the regulation of aerobic and anaerobic metabolisms through the ArcA/ArcB signal transduction system.
We cloned TaABC1L, an abiotic stress-responsive gene, from common wheat with a combination of reverse Northern blot screening, bioinformatics and RT-PCR strategies. A candidate EST, which was all up-regulated at 1, 6, and 12 h water stress, was selected from the cDNA library constructed with mRNA isolated from the 2-leaf seedling of Hanxuan 10 treated with 1 h water stress, by reverse Northern blotting. The candidate EST was extended by in silico cloning, and the full-length cDNA sequence, containing a 1 434 bp open reading frame, was obtained. The cDNA encodes a polypeptide of 477 amino acids with a calculated molecular mass of 54.55 kD and isoelectric point (pI) of 8.34. Sequence analysis indicated this putative protein includes ABC1 characteristic domain architecture (123–243 aa) and AARF domain (42–369 aa), but ABC1 precursor mitochondrion transit peptide (PD017350) was not observed. Therefore the gene was designated TaABC1L (TaABC1-like). Multiple alignment results showed that TaABC1L shared a homology of 88%, 81% with ABC1L and ABC transporter-like protein from Oryza sativa, and 62%, 62% with two unknown protein from Arabidopsis thaliana, respectively. The expression pattern of TaABC1L at transcription level was investigated by real-time quantitative RT-PCR, which revealed that TaABC1L was distinctly responsive to hyperosmolality (－0.5 MPa, PEG-6000), high salinity (250 mmol L^-1 NaCl), low temperature (4℃) stresses and abscisic acid (50 µmol L^-1 ABA) treatment. Expressional peaks of TaABC1L responsed to PEG, NaCl and 4℃ stresses appeared at 24, 1, and 48 h, with 13.9-, 30-, and 9.8-fold as high as that of the control, respectively. However, the expressional intensity of the peak with 12 h ABA treatment was only 2-fold as high as that of the control. Our studies strongly suggested that TaABC1L could respond to environmental stresses including salinity, low temperature, osmotic stresses and exogenous ABA treatment.

Key words: Wheat, ABC1L, Cloning, Abiotic stress, Expression