Local expression of enzymatically active class I beta-1, 3-glucanase enhances symptoms of TMV infection in tobacco.
Mutant tobacco plants deficient for class I beta-1,3-glucanase (GLU I) are decreased in their susceptibility to virus infection. This is correlated with delayed virus spread, a reduction in the size exclusion limit of plasmodesmata and increased cell-wall deposition of the beta-1,3-glucan callose. To further investigate a role of GLU I during cell-to-cell movement of virus infection, we inserted the GLU I coding sequence into TMV for overexpression in infected cells. Compared with the size of local lesions produced on plants infected with virus expressing either an enzymatically inactive GLU I or a frameshift mutant of the gene, the size of local lesions caused by infection with virus expressing active GLU I was consistently increased. Viruses expressing antisense GLU I constructs led to lesions of decreased size. Similar effects were obtained for virus spread using plants grown at 32 degrees C to block the hypersensitive response. Together, these results indicate that enzymatically active GLU I expressed in cells containing replicating virus can increase cell-to-cell movement of virus. This supports the view that GLU I induced locally during infection helps to promote cell-to-cell movement of virus by hydrolyzing callose. Moreover, our results provide the first direct evidence that a biological function of a plant beta-1,3-glucanase depends on its catalytic activity.
Bucher
G L
GL
Friedrich Miescher Institute, Novartis Research Foundation, Maulbeerstrasse 66, CH-4058 Basel, Switzerland.
Tarina
C
C
Heinlein
M
M
Di Serio
F
F
Meins
F
F
Iglesias
V A
VA
D001692:Biological Transport; D005822:Genetic Vectors; D043326:Glucan 1,3-beta-Glucosidase; D005936:Glucans / Q000235:genetics / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000096:biosynthesis / Q000378:metabolism*; D009154:Mutation; D053830:Plant Viral Movement Proteins; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism / Q000821:virology*; D017898:Tobamovirus / Q000472:pathogenicity*; D014764:Viral Proteins
D005936:Glucans; D053830:Plant Viral Movement Proteins; D014764:Viral Proteins; C048306:callose; D006026:Glycoside Hydrolases; D043326:Glucan 1,3-beta-Glucosidase; C117648:beta-1,3-exoglucanase