Isolation and characterization of a gene encoding a polyethylene glycol-induced cysteine protease in common wheat.

Plant cysteine protease (CP) genes are induced by abiotic stresses such as drought, yet their functions remain largely unknown. We isolated the full-length cDNA encoding a Triticum aestivum CP gene, designated TaCP, from wheat by the rapid amplification of cDNA ends (RACE) method. Sequence analysis revealed that TaCP contains an open reading frame encoding a protein of 362 amino acids, which is 96% identical to barley cysteine protease HvSF42. The TaCP transcript level in wheat seedlings was upregulated during polyethylene glycol (PEG) stress, with a peak appearing around 12 h after treatment. TaCP expression level increased rapidly with NaCl treatment at 48 h. TaCP responded strongly to low temperature (4 degree C) treatment from 1 h post-treatment and reached a peak of about 40-fold at 72 h. However, it showed only a very slight response to abscisic acid (ABA). More than one copy of TaCP was present in each of the three genomes of hexaploid wheat and its diploid donors. TaCP fused with green fluorescent protein (GFP) was located in the plasma membrane of onion epidermis cells. Transgenic Arabidopsis plants overexpressing TaCP showed stronger drought tolerance and higher CP activity under water-stressed conditions than wild-type Arabidopsis plants. The results suggest that TaCP plays a role in tolerance to water deficit.

[A preliminary study on gene expression profile induced by water stress in wheat (Triticum aestivum L.) seedling].

In the present research, suppression subtractive hybridization (SSH) and high density membrane techniques were employed to analysis genes induced by water stress in wheat seedling at 2-leaf stage. The purpose was to comprehensively understand the genetic bases of drought resistance and to find the key genes related to drought resistance in wheat. A total of 181 positive clones were obtained by screening the SSH library including 1 530 individual recombinant clones. The result of the sequence homologous comparison and function querying showed that 83.2% differentially expressed genes were high homologous with those induced by abiotic or biotic stresses in plant and their functions were to protect the cell directly or indirectly from stress strain. Seventeen differentially expressed ESTs found first were registered in GenBank. After further identifying by reverse Northern, RT-PCR and Northern, the gene expression profile induced by water stress in wheat seedling was preliminarily revealed.