Submitted to: Plant and Animal Genome Conference
Publication Type: Abstract Only
Publication Acceptance Date: 10/3/2004
Publication Date: 1/15/2005
Citation: Zhu, J., Zou, J., Aldea, M., Delucia, E., Clough, S.J. 2005. Down regulation of chloroplast genes specific to hr. [abstract]. Proceedings of the Plant and Animal Genome XIII Conference; San Diego, California Jan. p. 242.
Technical Abstract: Soybean [Glycine max (L.) Merrill] plants were inoculated with strains of Pseudomonas syringae that were either virulent (VIR) or were recognized by the R-gene mediated host defense system inducing the hypersensitive defense response (HR). Unifoliate leaves were vacuum infiltrated with approximately 2x10e7 cells per ml and tissue collected at 2, 4, 8, and 24 hours post inoculation (hpi). Gene expression profiles indicated that polyA RNAs of nearly 100 nuclear-encoded chloroplast genes were of lower abundance in tissue inoculated with the HR-inducing strains versus tissue inoculated with the virulent strain. The decrease in chloroplast-related transcripts was apparent at the 4, but not the 2 hpi time point. To determine if photosynthesis was also affected, we used a 1 ml syringe to force inoculum into leaf apoplastic spaces and measured the spatial pattern of chlorophyll fluorescence. In this manner, four treatments (HR, VIR, suspension solution, and null) could be measured simultaneously on the same leaf within a single image field. Photosynthetic measurements were consistent with an HR-specific reduction in photosystem II operating efficiency (Phi PSII) that became apparent 4 to 5 hours post inoculation. Reduced Phi PSII was more pronounced at 8 than 4 hpi for the HR treatment with little effect in the other treatments at these time points. Preliminary analyses suggest that the decreased Phi PSII was a result of an increase in non-photochemical quenching and might be one source of the increased levels of reactive oxygen species known to occur during HR.