Vascular defense responses in rice: peroxidase accumulation in xylem parenchyma cells and xylem wall thickening

• Published in: Molecular plant-microbe interactions Vol. 14; no. 12; pp. 1411 - 1419
• Main Authors: Hilaire, E., Young, S. A., Willard, L. H., McGee, J. D., Sweat, T., Chittoor, J. M., Guikema, J. A., Leach, J. E.
• Format: Journal Article
• Language: English
• Published: Legacy CDMS APS Press 01-12-2001; The American Phytopathological Society
• Subjects: Amino Acid Sequence; Bacterial plant pathogens; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Plant; Immunity, Innate - physiology; Life Sciences (General); lignification; Molecular Sequence Data; Oryza - enzymology; Oryza - microbiology; Oryza - physiology; Oryza sativa; Pathology. Damages, economic importance; peroxidase; Peroxidases - genetics; Peroxidases - metabolism; Phytopathology. Animal pests. Plant and forest protection; pit aperture; Sequence Alignment; Sequence Homology, Amino Acid; Space life sciences; Xanthomonas - pathogenicity; Xanthomonas oryzae; Nasa Discipline Plant Biology; Non-Nasa Center; Pseudomonadales; Monocotyledones; Xylem; Plant pathogen; Parenchyma; Cereal crop; Cell wall; Oryza sativa; Disease resistance; Inoculation; Microorganism resistance; Lignification; Gramineae; Angiospermae; Bacteria; Pseudomonadaceae; Peroxidase; Conductive tissue; Thickening; Enzyme; Host agent relation; Gene expression; Sensitivity resistance; Peroxidases; Defense mechanism; Spermatophyta; Xanthomonas oryzae pv. oryzae; Oxidoreductases; Biological accumulation; NASA Discipline Plant Biology; Non-NASA Center
• ISSN: 0894-0282; 1943-7706
• DOI: 10.1094/mpmi.2001.14.12.1411

The rice bacterial blight pathogen Xanthomonas oryzae pv. oryzae is a vascular pathogen that elicits a defensive response through interaction with metabolically active rice cells. In leaves of 12-day-old rice seedlings, the exposed pit membrane separating the xylem lumen from the associated parenchyma cells allows contact with bacterial cells. During resistant responses, the xylem secondary walls thicken within 48 h and the pit diameter decreases, effectively reducing the area of pit membrane exposed for access by bacteria. In susceptible interactions and mock-inoculated controls, the xylem walls do not thicken within 48 h. Xylem secondary wall thickening is developmental and, in untreated 65-day-old rice plants, the size of the pit also is reduced. Activity and accumulation of a secreted cationic peroxidase, PO-C1, were previously shown to increase in xylem vessel walls and lumen. Peptide-specific antibodies and immunogold-labeling were used to demonstrate that PO-C1 is produced in the xylem parenchyma and secreted to the xylem lumen and walls. The timing of the accumulation is consistent with vessel secondary wall thickening. The PO-C1 gene is distinct but shares a high level of similarity with previously cloned pathogen-induced peroxidases in rice. PO-C1 gene expression was induced as early as 12 h during resistant interactions and peaked between 18 and 24 h after inoculation. Expression during susceptible interactions was lower than that observed in resistant interactions and was undetectable after infiltration with water, after mechanical wounding, or in mature leaves. These data are consistent with a role for vessel secondary wall thickening and peroxidase PO-C1 accumulation in the defense response in rice to X. oryzae pv. oryzae.