Evaluation of transgenic 'Chardonnay' (Vitis vinifera) containing magainin genes for resistance to crown gall and powdery mildew.
Magainins, short peptides with broad-spectrum antimicrobial activity in vitro, were assayed for their ability to confer resistance to pathogens in transgenic grapevines. Embryogenic cell suspensions of 'Chardonnay' (Vitis vinifera L.) were co-transformed by microprojectile bombardment with a plasmid carrying the npt-II gene and a second plasmid harboring either a natural magainin-2 (mag2) or a synthetic derivative (MSI99) gene. Magainin genes and the marker gene were driven by Arabidopsis ubiquitin-3 and ubiquitin-11 promoters, respectively. A total of 10 mag2 and 9 MSI99 regenerated lines were studied by Southern blot hybridization, which showed 1-6 transgene integration events into the plant genome. Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) revealed a variable range in transcription levels among mag2 and MSI99 lines. A positive correlation between number of integration events and transcription level was observed (p<0.05). Plants were acclimated and challenged in the greenhouse with either Agrobacterium vitis strains (bacterial crown gall pathogen) at 10(8) cfu/ml or Uncinula necator (fungal powdery mildew pathogen) at 10(5) conidia/ml for evaluation of disease resistance. A total of 6 mag2 and 5 MSI99 lines expressing the antimicrobial genes exhibited significant reductions of crown gall symptoms as compared to non-transformed controls. However, only two mag2 lines showed measurable symptom reductions in response to U. necator, but not strong resistance. Our results suggest that the expression of magainin-type genes in grapevines may be more effective against bacteria than fungi. Additional strategies to enhance transgene expression and the spectrum of resistance to grape diseases are suggested.
Vidal
José R
JR
Department of Horticultural Sciences, New York State Agricultural Experiment Station, Cornell University, Geneva, NY 14456, USA.
Kikkert
Julie R
JR
Malnoy
Mickael A
MA
Wallace
Patricia G
PG
Barnard
John
J
Reisch
Bruce I
BI
D000595:Amino Acid Sequence; D023181:Antimicrobial Cationic Peptides / Q000235:genetics* / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics; D015139:Blotting, Southern; D008969:Molecular Sequence Data; D010455:Peptides / Q000235:genetics* / Q000502:physiology; D010941:Plant Tumors / Q000235:genetics* / Q000382:microbiology*; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012231:Rhizobium / Q000472:pathogenicity; D027843:Vitis / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology
D023181:Antimicrobial Cationic Peptides; C446524:MSI-99 peptide; D010455:Peptides; D011994:Recombinant Proteins