Silencing of acidic pathogenesis-related PR-1 genes increases extracellular beta-(1->3)-glucanase activity at the onset of tobacco defence reactions.
The class 1 pathogenesis-related (PR) proteins are thought to be involved in plant defence responses, but their molecular functions are unknown. The function of PR-1 was investigated in tobacco by generating stable PR-1a-silenced lines in which other acidic PR-1 genes (PR-1b and PR-1c) were silenced. Plants lacking extracellular PR-1s were more susceptible than wild-type plants to the oomycete Phytophthora parasitica but displayed unaffected systemic acquired resistance and developmental resistance to this pathogen. Treatment with salicylic acid up-regulates the PR-1g gene, encoding a basic protein of the PR-1 family, in PR-1-deficient tobacco, indicating that PR-1 expression may repress that of PR-1g. This shows that acidic PR-1s are dispensable for expression of salicylic acid-dependent acquired resistances against P. parasitica and may reveal a functional overlap in tobacco defence or a functional redundancy in the PR-1 gene family. The data also show that there is a specific increase in apoplastic beta-(1-->3)-glucanase activity and a decrease in beta-(1-->3)-glucan deposition in PR-1-silenced lines following activation of defence reactions. Complementation of the silencing by apoplastic treatment with a recombinant PR-1a protein largely restores the wild-type beta-(1-->3)-glucanase activity and callose phenotype. Taken together with the immunolocalization of PR-1a to sites of beta-(1-->3)-glucan deposition in wild-type plants, these results are indicative of a function for PR-1a in regulation of enzymatic activity of extracellular beta-(1-->3)-glucanases.
Rivière
Marie-Pierre
MP
UMR 1301 Interactions Biotiques et Santé Végétale, INRA-Université Nice-SophiaAntipolis-CNRS, F-06903 Sophia Antipolis Cedex, France.
Marais
Antoine
A
Ponchet
Michel
M
Willats
William
W
Galiana
Eric
E
D020418:Algal Proteins / Q000494:pharmacology; D005656:Fungal Proteins; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects; D005816:Genetic Complementation Test; D043326:Glucan 1,3-beta-Glucosidase / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005936:Glucans / Q000378:metabolism; D007113:Immunity, Innate; D008969:Molecular Sequence Data; D010838:Phytophthora; D010935:Plant Diseases / Q000235:genetics; D010940:Plant Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*; D030821:Plants, Genetically Modified; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference / Q000187:drug effects; D011994:Recombinant Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D020156:Salicylic Acid / Q000494:pharmacology; D014026:Nicotiana / Q000201:enzymology* / Q000235:genetics / Q000276:immunology* / Q000469:parasitology; D015854:Up-Regulation / Q000187:drug effects
D020418:Algal Proteins; D005656:Fungal Proteins; D005936:Glucans; D010940:Plant Proteins; D020033:Protein Isoforms; D011994:Recombinant Proteins; C061032:cryptogein protein, Phytophthora cryptogea; C053376:pathogenesis-related proteins, plant; C048306:callose; D043326:Glucan 1,3-beta-Glucosidase; D020156:Salicylic Acid