RESUMO
The inhibition of elicitor-induced plant defense responses by the protein kinase inhibitors K252a and staurosporine indicates that defense responses require protein phosphorylation. We isolated a cDNA clone encoding Nicotiana tabacum lectin-like receptor protein kinase 1 (NtlecRK1), an elicitor-responsive gene; in tobacco bright yellow (BY-2) cells by a differential display method. NtlecRK forms a gene family with at least three members in tobacco. All three NtlecRK genes potentially encode the N-terminal legume lectin domain, transmembrane domain and C-terminal Ser/Thr-type protein kinase domain. Green fluorescent protein (GFP) fusion showed that the NtlecRK1 protein was located on the plasma membrane. In addition, NtlecRK1 and 3 were responsive to INF1 elicitin and the bacterial elicitor harpin. These results indicate that NtlecRKs are membrane-located protein kinases that are induced during defense responses in BY-2 cells.
Assuntos
Proteínas de Algas/farmacologia , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Proteínas de Plantas/genética , Proteínas Quinases/genética , Sequência de Aminoácidos , Linhagem Celular , Membrana Celular/metabolismo , Dados de Sequência Molecular , Fosforilação , Proteínas de Plantas/metabolismo , Proteínas Quinases/metabolismo , Estrutura Terciária de Proteína , Proteínas , NicotianaRESUMO
SUMMARY: Non-host resistance is the most general form of disease resistance in plants because it is effective against most phytopathogens. The importance of hypersensitive responses (HRs) in non-host resistance of Nicotiana species to the oomycete Phytophthora is clear. INF1 elicitin, an elicitor obtained from the late-blight pathogen Phytophthora infestans, is sufficient to induce a typical HR in Nicotiana species. The molecular mechanisms that underlie the non-host resistance component of plant defence responses have been investigated using differential-display polymerase chain reaction (PCR) in a model HR system between INF1 elicitin and tobacco BY-2 cells. Differential-display PCR has revealed that Cdc27B is down-regulated in tobacco BY-2 cells after treatment with INF1 elicitin. Cdc27B is one of 13 essential components of the anaphase-promoting complex or cyclosome (APC/C)-type E3 ubiquitin ligase complex in yeast. This APC/C-type E3 ubiquitin ligase complex regulates G2-to-M phase transition of the cell cycle by proteolytic degradation. In this study, we investigated the roles of this gene, NbCdc27B, in plant defence responses using virus-induced gene silencing. Suppression of NbCdc27B in Nicotiana benthamiana plants induced defence responses and a gain of resistance to Colletotrichum lagenarium fungus. Elicitin-induced hypersensitive cell death (HCD) was inhibited mildly in plants silenced with tobacco rattle virus::Cdc27B. Cdc27B could manage the signalling pathways of plant defence responses as a negative regulator without HCD.
