Pathogenesis-related acidic beta-1,3-glucanase genes of tobacco are regulated by both stress and developmental signals.
Three pathogenesis-related (PR) proteins of tobacco are acidic isoforms of beta-1,3-glucanase (PR-2a, -2b, -2c). We have cloned and sequenced a partial cDNA clone (lambda FJ1) corresponding to one of the PR-2 beta-1,3-glucanases. A small gene family encodes the PR-2 proteins in tobacco, and similar genes are present in a number of plant species. We analyzed the stress and developmental regulation of the tobacco PR-2 beta-1,3-glucanases by using northern and western analyses and a new technique to assay enzymatic activity. Stress caused by both thiamine and tobacco mosaic virus (TMV) infection resulted in a dramatic increase in the levels of PR-2 mRNA, protein, and enzyme activities. The increased PR-2 gene expression in upper uninoculated leaves of plants infected with TMV also suggests a role in systemic acquired resistance. During floral development, a number of beta-1,3-glucanase activities were observed in all flower tissues. However, PR-2 polypeptides were observed only in sepal tissue. In contrast, an mRNA that hybridized to the PR-2 cDNA was present in stigma/style tissue and the sepals. Primer extension analysis confirmed the identity of the PR-2 mRNA in sepals, but indicated that the beta-1,3-glucanase gene expressed in the stigma/style of flowers was distinct from the PR-2 genes. The induction of PR-2 protein synthesis by both stress and developmental signals was accompanied by a corresponding increase in the steady-state levels of PR-2 mRNA, suggesting that PR-2 gene expression is regulated, in part, at the level of mRNA accumulation.
Département de Phytologie, Faculté des Sciences de l'Agriculture et de l'Alimentation, Université Laval, Sainte-Foy, Québec, Canada.
F
F
Côté
J R
JR
Cutt
A
A
Asselin
D F
DF
Klessig
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA; D004591:Electrophoresis, Polyacrylamide Gel; D015971:Gene Expression Regulation, Enzymologic; D043326:Glucan 1,3-beta-Glucosidase; D008969:Molecular Sequence Data; D005810:Multigene Family; D010935:Plant Diseases; D010940:Plant Proteins / Q000235:genetics*; D010947:Plants, Toxic; D013831:Thiamine / Q000502:physiology; D014026:Nicotiana / Q000235:genetics* / Q000254:growth & development / Q000382:microbiology; D014027:Tobacco Mosaic Virus / Q000502:physiology; D001617:beta-Glucosidase / Q000235:genetics* / Q000378:metabolism
D010940:Plant Proteins; C053376:pathogenesis-related proteins, plant; D004247:DNA; D001617:beta-Glucosidase; D043326:Glucan 1,3-beta-Glucosidase; D013831:Thiamine