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Protein kinases play crucial roles in response to external environment stress signals. A putative protein kinase, W55a, belonging to SNF1-related protein kinase 2 ( SnRK2) subfamily, was isolated from a cDNA library of drought-treated wheat seedlings. The entire length of W55a was obtained using rapid amplification of 5′ cDNA ends ( 5′-RACE) and reverse transcription-polymerase chain reaction( RT-PCR). It contains a 1 029 -bp open reading frame ( ORF) encoding 342 amino acids. The deduced amino acid sequence of W55a had eleven conserved catalytic subdomains and one Ser/Thr protein kinase active-site that characterize Ser/Thr protein kinases. Phylogenetic analysis showed that W55a was 90.38% homologous with rice SAPK1, a member of the SnRK2 family. Using nullisomic-tetrasomic and ditelocentric lines of Chinese Spring, W55a was located on chromosome 2BS. Expression pattern analysis revealed that W55a was upregulated by drought and salt, exogenous abscisic acid, salicylic acid, ethylene and methyl jasmonate, but was not responsive to cold stress. In addition, W55a transcripts were abundant in leaves, but not in roots or stems, under environmental stresses. Transgenic Arabidopsis plants overexpressing W55a exhibited higher tolerance to drought. Based on these findings, W55a encodes a novel dehydration-responsive protein kinase that is involved in multiple stress signal transductions. [ABSTRACT FROM AUTHOR]

The xylA gene, encoding xylose isomerase, was cloned as a 1342-bp BamHI/SacI fragment from the E. coli. As a selection marker, the xylA gene was fused between the enhanced CaMV 35S promoter (E35S) and terminator (35St) in pBAC413 (Fig.2). pBAC413 was constructed to prevent the expression of sbeIIb in maize. PDS1000/He was used to bombard maize calli, which were induced to form by the elite inbred lines. The selection was carried out on the media containing concentrations of xylose from 0 to 100%. The results showed that the media containing 50% to 100% D-xylose were better, but differed with the genotype of maize (Tables 1 and 2). Successful integration of xylA gene into the maize genome was confirmed by DNA dot blotting, PCR and PCR-Southern hybridization (Figs.4 to 6). A method was established in which transformed maize cells were successively screened on a medium containing xylose instead of antibiotic and herbicide for bio-safety.

Plant-pathogen interaction is the more important phytopathological subjects. Landmark progress in the past 10 years have resulted in the identification of functional R genes from the host and Avr genes from the pathogen,additionally interaction between their encoded productions. This paper reviewed the two models of R-Avr interaction, namely "receptor-ligand model" and "guard model", and discussed how to utilize the R gene during crop breeding and commercial production.