The lower cell density of leaf parenchyma in the Arabidopsis thaliana mutant lcd1-1 is associated with increased sensitivity to ozone and virulent Pseudomonas syringae.
Under optimal growth conditions (120 micro mol photons m-2 sec-1 photosynthetically active radiation (PAR), 16-h photoperiod), the recessive ozone-sensitive Arabidopsis thaliana L. Heynh. mutant lcd1-1 exhibits a pale phenotype compared to the wild type. Confocal and multiphoton microscopy revealed that the paleness of lcd1-1 is because of a lower cell density in the leaf palisade parenchyma, resulting in decreased chlorophyll content. When exposed to ozone, lcd1-1 leaves become paler and contain an increased amount of the lipid peroxidation product malondialdehyde compared to the wild type, suggesting that lcd1-1 suffers from elevated levels of reactive oxygen species (ROS) generated in the apoplast. Infection of leaves with virulent Pseudomonas syringae reveals higher bacterial growth as well as lower pathogenesis-related protein 1 (PR-1) and PR-5 expression in lcd1-1 than in the wild type. When the wild type and lcd1-1 are exposed to short-term high-light stress, leaves do not bleach in lcd1-1 and potential activities of photosystems I (PSI) and II (PSII) decrease to a similar extent in both the genotypes, indicating that the photosynthetic apparatus is not affected by lcd1-1 mutation. The LCD1 gene, found to contain a nonsense mutation in the mutant, has been identified. It is located at the bottom of chromosome 2 of the Arabidopsis genome. However, the function of the protein encoded by LCD1 is not yet known. We hypothesize that LCD1 plays a role in normal leaf development, and that the increased sensitivity to ozone and virulent P. syringae is a secondary effect that presumably results from the lower-cell-density phenotype in lcd1-1.
Barth
Carina
C
Boyce Thompson Institute for Plant Research, Tower Road, Ithaca, NY 14853, USA.
Conklin
Patricia L
PL
D000222:Adaptation, Physiological / Q000187:drug effects; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D018533:Biomass; D002734:Chlorophyll / Q000378:metabolism; D008027:Light; D045342:Light-Harvesting Protein Complexes; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D009154:Mutation; D010126:Ozone / Q000494:pharmacology*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000382:microbiology / Q000502:physiology*; D010940:Plant Proteins / Q000378:metabolism; D011549:Pseudomonas / Q000472:pathogenicity*; D017382:Reactive Oxygen Species / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014774:Virulence
D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D010940:Plant Proteins; D017382:Reactive Oxygen Species; C053376:pathogenesis-related proteins, plant; D002734:Chlorophyll; D010126:Ozone