Novel genes for disease-resistance breeding Melchers, Leo S; Stuiver, Maarten H
Current Opinion in Plant Biology,
04/2000, Letnik:
3, Številka:
2
Book Review, Journal Article
Recenzirano
Plant disease control is entering an exciting period during which transgenic plants showing improved resistance to pathogenic viruses, bacteria, fungi and insects are being developed. This review ...summarizes the first successful attempts to engineer fungal resistance in crops, and highlights two promising approaches. Biotechnology provides the promise of new integrated disease management strategies that combine modern fungicides and transgenic crops to provide effective disease control for modern agriculture.
In a search for novel plant-derived antimicrobial proteins, we screened extracts from salicylic acid (SA)-treated lettuce and sunflower leaves. These extracts displayed very potent antimicrobial ...activity against a set of phytopathogens. Characterisation of these extracts revealed that in both extracts, proteins of approximately 60 kDa were responsible for the antimicrobial activity. Further characterisation of these proteins and cloning of the respective cDNAs revealed close homology to a range of (plant) oxidases. Dissection of the enzymatic activity of both proteins revealed them to be carbohydrate oxidases (Helianthus annuus carbohydrate oxidase (Ha-CHOX) and Lactuca sativa carbohydrate oxidase (Ls-CHOX)) with broad substrate specificity and with hydrogen peroxide (H2O2) as one of the reaction products. The sunflower transcript, in addition to being SA inducible, was also inducible by fungal pathogens but not by ethylene and jasmonate. To determine whether Ha-CHOX plays a role in pathogen defence, it was transformed into tobacco and the effect of resistance to Pectobacterium carotovorum ssp. carotovorum was examined. Transgenic plants overexpressing Ha-CHOX displayed enhanced resistance to infection by this pathogen, and the resistance level was proportional to enzyme expression.
Summary
Many events associated with the plant defence responses are regulated on the transcriptional level. Here we report the results of a promoter tagging approach to identify promoters that are ...induced upon pathogen attack in Arabidopsis thaliana. A line was identified in a T‐DNA UidA tagged Arabidopsis library with induced GUS expression after Botrytis cinerea infection around the site of fungal infection. The upstream sequence was isolated and fused to the UidA gene and tested in transgenic Arabidopsis thaliana and Brassica napus plants. Promoter function was very similar to the expression pattern found in the original promoter tagged line. We found that the promoter sequence was located on Arabidopsis chromosome III and linked to a predicted open reading frame in the reverse orientation. The predicted gene codes for a putative receptor serine threonine protein kinase of 383 amino acids in size. The clone contains a protein kinase ATP binding region, a protein kinase active site, a region with similarity to motifs found in Alpha Isopropylmalate/homocitrate synthase enzymes and a putative leucine zipper motif. Analysis of the expression pattern of the gene using RT‐PCR demonstrated that the putative receptor serine threonine protein kinase is up‐regulated after Salicylic acid treatment and Botrytis infection.
Streptomyces lividans, S. coelicolor and S. griseofuscus were examined for the presence of the enzymes of the phosphoenolpyruvate:sugar phosphotransferase system (PTS). All three species were shown ...to possess Enzyme I, HPr and fructose-specific Enzyme II (IIFru) activities. In S. lividans and S. coelicolor, all three PTS enzymes were fructose-inducible, but in S. griseofuscus the system was expressed constitutively. These organisms apparently lack the HPr(Ser) kinase and HPr(Ser-P) phosphatase that characterize low-GC Gram-positive bacteria.
We have isolated a cDNA encoding the 84-kD subunit of NFIV. Tryptic peptide sequences were identified within the coding sequences, confirming its proper identity. The primary sequence of the protein ...is identical to that of the large subunit of the Ku autoantigen. A missing NFIV peptide sequence was identified within the sequence of the small subunit of Ku. In addition, the proteins are identical in immunological aspects. We suggest that the Ku and NFIV proteins are identical. This connection adds new biochemical data to our knowledge of the Ku autoantigen.
The Adenovirus DNA binding protein (DBP) imposes a regular, rigid and extended conformation on single stranded DNA (ssDNA) and removes secondary structure. Here we show that DBP promotes renaturation ...of complementary single DNA strands. Enhancement of intermolecular renaturation is sequence independent, can be observed over a broad range of ionic conditions and occurs only when the DNA strands are completely covered with DBP. When one strand of DNA is covered with DBP and its complementary strand with T4 gene 32 protein, renaturation is still enhanced compared to protein-free DNA, indicating that the structures of both protein-DNA complexes are compatible for renaturation. In contrast to promoting intermolecular renaturation, DBP strongly inhibits intramolecular renaturation required for the formation of a panhandle from an ssDNA molecule with an inverted terminal repeat. We explain this by the rigidity of an ssDNA-DBP complex. These results will be discussed in view of the crystal structure of DBP that has recently been determined.
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