GrainGenes Reference Report: PMP-46-1
Reference
PMP-46-1
Title
Epidermal cell cytoplasmic events and response gene transcript accumulation during Erysiphe graminis attach in isogenic barley lines differing at the Ml-o-locus
Journal
Physiology and Molecular Plant Pathology
Year
1995
Volume
46
Pages
1-16
Author
Clark T Zeyen R Carver T Smith A Bushnell W
Abstract
Patterns in the accumulation of six host response gene transcripts were determined at various time intervals, 0-48 h after inoculation of leaves with Erysiphe graminis f.sp hordei in two near-isogenic barley lines, RISO 5678 R (RISO-R) (resistant) and RISO 5678 S (RISO-S) (susceptible), differing at the ml-o locus for resistance At each time interval, leaf tissue was fixed and stained for light microscopy of fungal development and host epidermal cell response to E graminis Resistance in the recessive ml-o line was expressed by failure of fungal germlings to penetrate host epidermal cells fully and produce haustoria and was correlated with deposition of papillae at sites of attack. Transcripts of the six host response genes usually accumulated in a biphasic pattern, as determined by quantitative radioanalysis of northern blots. The initial peak of activity was observed at 4-6 h (the time of cytoplasmic aggregation and papilla deposition beneath tips of the primary germ tubes). The second peak was observed at 12-l5 h the time of cytoplasmic aggregation and papilla deposition beneath the tips of the appressonria. The time and magnitude of peaks of cytoplasmic aggregation and papilla deposition was the same in RISO-R and RISO-S as were patterns of response gene transcript accumulation. There were no pattern differences in transcript accumulation that could be directly attributed to differences at the Ml-o locus. The results indicate that the response genes were activated and transcribed as a general defence response to attempted penetration by the fungus because they occur in both isolines. 0452-86960 NADPH-dependent O2- generating activity of a plasma membrane-rich. (PM) fraction from potato tuber tissue was measured an in vitro using measurements of superoxide dismutase (SOD) and catalase-sensitive O2 consumption and/or spectrophotometnc measurements of SOD-sensitive cytochrome c (acetylated) reduction. The enhanced NADPH-dependent O2- generating activity was found predominantly in the plasma membrane fraction isolated from the potato tuber slices which had been inoculated with an incompatible race of Phytophthora infestans or treated with hyphal wall elicitor (HWC-elicitor) from the fungus. No enhanced activity was detected in plasma membrane fractions prepared from tuber tissues inoculated with a compatible race or left untreated. The enhanced activity in the isolated PM fraction was not dependent on Ca2+. In an in vitro system containing the plasma membrane fraction and a soluble cytosol protein fraction from control tuber tissue slices, CaCl2, MgCl2 and ATP, the NADPH-dependent O2- generating reaction was slowly or rapidly activated by treatment with HWC-el icitor or digitonin, respectively. In the in vitro system, from which one of either plasma membrane fraction, soluble cytosol protein, Ca2+ or ATP was removed, no in vitro activation of NADPH-dependent O2- generating reaction occurred after treatment with HWC-elicitor or digitonin. These results indicate that a novel O2- generating NADPH oxidasc may be activated in the plasma membrane of potato cells by inoculauon with an incompatible race of P. infestans or treatment with the fungal elicitor and that Ca2+, cytosolic protein components and ATP may be involved in the activation process.
Keyword
cell-structure
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GrainGenes Reference Report: PMP-46-1
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GrainGenes is a product of the Agricultural Research Service of the US Department of Agriculture. | |||