Wen, Fushi , Rivera-Curlango, Gilberto , VanEtten, Hans D. , Hawes, Martha C. .
Extracellular 14-3-3 Proteins: Role in Root Tip Resistance to Fungal Infection.
Plant root tips are “immune” to most pathogens; this immunity is essential for healthy plant roots, and therefore for whole plant development. We reported recently that the root cap and a specialized group of cells surrounding the root cap--root border cells--play a major role in protecting the root tip by secreting proteins into the extracellular environment (Plant Physiol 143:773). Among this root cap 'secretome' is 14-3-3 protein, a eucaryotic regulatory protein involved in diverse intracellular processes. A 'scaffold' of 14-3-3 proteins was visualized as a component of the border cell capsule using immunolocalization. Little is known about extracellular 14-3-3 proteins, recently discovered in human fibroblasts and Chlamydomonas cell walls. When pea root tips were treated with R18, high-affinity peptide antagonist of 14-3-3 protein, root tip resistance to infection by a pea fungal pathogen, Nectria haematocacca, was significantly reduced. In this study, a polyclonal antibody of 14-3-3 protein caused a similar increase in root tip infection. India ink was used to measure and monitor changes in the extracellular border cell capsule (e.g. J Bacteriol 180:52). The size of the pea and corn border cell capsule increased by 3-5X, respectively, in response to co-cultivation with Nectria haematocacca and Pseudomonas aeuroginosa. A >50X increase occurred on border cells of corn grown in hydroponic culture in the presence of Bacillus subtilis. Proteinase K treatment almost completely eliminated the capsule, whose size also was reduced by R18. These data indicate that protein is a key structural as well as functional component of the border cell capsule, and support the hypothesis that extracellular 14-3-3 proteins play a major role in root tip resistance to infection.
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1 - University of Arizona, Plant Sciences, 9291 E. Shonto Lane, Tucson, AZ, 85749, usa
2 - University of Arizona, Plant Sciences
extracellular 14-3-3 protein
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM