RESUMO
Plant-endoparasitic root-knot nematodes feed on specialized giant cells that they induce in the vascular cylinder of susceptible plants. Although it has been established that a number of plant genes change their expression pattern during giant cell differentiation, virtually no data are available about the mechanisms involved in that change. One possibility is differential promoter recognition by the transcription factor(s) responsible for the expression of specific genes. We have isolated and characterized a genomic clone from tomato containing the promoter region of LEMMI9, one of the few plant genes that have been reported to be highly expressed in galls (predominantly in giant cells). The analysis of transgenic potato plants carrying a LEMMI9 promoter-beta glucuronidase (GUS) fusion has demonstrated that the tomato promoter was activated in Meloidogyne incognita-induced galls in a heterologous system. We have located putative regulatory sequences in the promoter and have found that nuclear proteins from the galls formed specific DNA-protein complexes with the proximal region of the LEMMI9 promoter. The nuclear protein-binding sequence mapped to a region of 111 bp immediately upstream from the TATA box. This region contains a 12-bp repeat possibly involved in the formation of DNA-protein complexes, which might be related to the LEMMI9 transcriptional activation in the giant cells.
Assuntos
Genes de Plantas , Nematoides/patogenicidade , Regiões Promotoras Genéticas , Solanum lycopersicum/genética , Solanum lycopersicum/parasitologia , Animais , Sequência de Bases , Sítios de Ligação/genética , DNA de Plantas/genética , DNA de Plantas/metabolismo , Regulação da Expressão Gênica de Plantas , Solanum lycopersicum/metabolismo , Dados de Sequência Molecular , Proteínas Nucleares/metabolismo , Doenças das Plantas/genética , Doenças das Plantas/parasitologia , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas , Ligação Proteica , Solanum tuberosum/genéticaRESUMO
In the quest for plant regulatory sequences capable of driving nematode-triggered effector gene expression in feeding structures, we show that promoter tagging is a valuable tool. A large collection of transgenic Arabidopsis plants was generated. They were transformed with a beta-glucuronidase gene functioning as a promoter tag. Three T-DNA constructs, pGV1047, p delta gusBin19, and pMOG553, were used. Early responses to nematode invasion were of primary interest. Six lines exhibiting beta-glucuronidase activity in syncytia induced by the beet cyst nematode were studied. Reporter gene activation was also identified in galls induced by root knot and ectoparasitic nematodes. Time-course studies revealed that all six tags were differentially activated during the development of the feeding structure. T-DNA-flanking regions responsible for the observed responses after nematode infection were isolated and characterized for promoter activity.
Assuntos
Arabidopsis/genética , Arabidopsis/parasitologia , Genes de Plantas , Nematoides/patogenicidade , Animais , Sequência de Bases , Primers do DNA/genética , DNA Bacteriano/genética , Regulação da Expressão Gênica de Plantas , Genes Reguladores , Genes Reporter , Vetores Genéticos , Glucuronidase/genética , Doenças das Plantas/genética , Doenças das Plantas/parasitologia , Plantas Geneticamente Modificadas , Reação em Cadeia da Polimerase , Regiões Promotoras Genéticas , Ativação TranscricionalRESUMO
We have isolated a cDNA encoding a catalase (Cat2St) by differential screening of a cDNA library constructed from potato roots infected with the cyst nematode Globodera pallida. Expression analysis confirmed the local induction of Cat2St and showed that it was highest at the adult stage of the parasite. It also revealed that Cat2St was induced in uninfected roots, stems, and leaves of infected plants. Localized and systemic induction of Cat2St was also observed upon root-knot nematode (Meloidogyne incognita) and root bacteria (Erwinia carotovora, Corynebacterium sepedonicum) infections. Based on sequence and expression analysis, Cat2St was found to belong to the recently described class II of dicotyledonous catalases, suggesting that these catalase isoforms could also be pathogen induced. Plant-parasitic nematodes are known to induce, in the roots of their hosts, highly metabolic feeding cells that function as nutritional sinks. Whereas the local induction of Cat2St is probably a consequence of an oxidative stress of metabolic nature, the systemic induction of Cat2St shows striking similarities with the induction of systemic acquired resistance (SAR) genes. The possible role of catalase in compatible plant-pathogen interactions is discussed.
