Movement of plant viruses is delayed in a beta-1,3-glucanase-deficient mutant showing a reduced plasmodesmatal size exclusion limit and enhanced callose deposition.
Susceptibility to virus infection is decreased in a class I beta-1,3-glucanase (GLU I)-deficient mutant (TAG4.4) of tobacco generated by antisense transformation. TAG4.4 exhibited delayed intercellular trafficking via plasmodesmata of a tobamovirus (tobacco mosaic virus), of a potexvirus (recombinant potato virus X expressing GFP), and of the movement protein (MP) 3a of a cucumovirus (cucumber mosaic virus). Monitoring the cell-to-cell movement of dextrans and peptides by a novel biolistic method revealed that the plasmodesmatal size exclusion limit (SEL) of TAG4.4 was also reduced from 1.0 to 0.85 nm. Therefore, GLU I-deficiency has a broad effect on plasmodesmatal movement, which is not limited to a particular virus type. Deposition of callose, a substrate for beta-1,3-glucanases, was increased in TAG4.4 in response to 32 degrees C treatment, treatment with the fungal elicitor xylanase, and wounding, suggesting that GLU I has an important function in regulating callose metabolism. Callose turnover is thought to regulate plasmodesmatal SEL. We propose that GLU I induction in response to infection may help promote MP-driven virus spread by degrading callose.
Iglesias
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VA
Friedrich Miescher Institute, Basel, Switzerland.
Meins
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D001692:Biological Transport; D043326:Glucan 1,3-beta-Glucosidase; D005936:Glucans / Q000235:genetics / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D009154:Mutation; D053830:Plant Viral Movement Proteins; D010947:Plants, Toxic; D017863:Potexvirus / Q000472:pathogenicity*; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism / Q000821:virology*; D017898:Tobamovirus / Q000472:pathogenicity*; D014764:Viral Proteins / Q000378:metabolism; D043325:Xylan Endo-1,3-beta-Xylosidase; D014995:Xylosidases / Q000378:metabolism
D005936:Glucans; D053830:Plant Viral Movement Proteins; D014764:Viral Proteins; C048306:callose; D006026:Glycoside Hydrolases; D014995:Xylosidases; D043325:Xylan Endo-1,3-beta-Xylosidase; D043326:Glucan 1,3-beta-Glucosidase; C117648:beta-1,3-exoglucanase