ABSTRACT
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.
Subject(s)
Genes, Plant , Nematoda/pathogenicity , Promoter Regions, Genetic , Solanum lycopersicum/genetics , Solanum lycopersicum/parasitology , Animals , Base Sequence , Binding Sites/genetics , DNA, Plant/genetics , DNA, Plant/metabolism , Gene Expression Regulation, Plant , Solanum lycopersicum/metabolism , Molecular Sequence Data , Nuclear Proteins/metabolism , Plant Diseases/genetics , Plant Diseases/parasitology , Plant Proteins/metabolism , Plants, Genetically Modified , Protein Binding , Solanum tuberosum/geneticsABSTRACT
In a compatible interaction, root-knot nematodes (Meloidogyne) induce a sophisticated feeding site shortly after they have penetrated the plant root. The feeding site contains metabolically highly active giant cells. To gain insight into the molecular aspects that are typical for giant cells, a cDNA library from tomato roots infected with Meloidogyne incognita was differentially screened to find induced genes. Among the genes identified, two extensin genes (Lemmi8 and Lemmi11) and a Lea-like gene (Lemmi9) were studied further.
Subject(s)
Gene Expression Regulation, Plant , Genes, Plant , Plant Proteins/genetics , Plant Roots/parasitology , Tylenchoidea/pathogenicity , Amino Acid Sequence , Animals , Base Sequence , Gene Library , Glycoproteins/genetics , Host-Parasite Interactions , In Situ Hybridization , Solanum lycopersicum , Molecular Probe Techniques , Molecular Sequence Data , Selection, Genetic , Sequence Analysis, DNAABSTRACT
The vast majority of proteins in the nematode cuticle are collagens. Cuticular collagen-encoding genes (col) have been described for the animal parasites Ascaris suum and Haemonchus contortus and for the free-living Caenorhabditis elegans. The proteins encoded by all these genes seem to have the same basic structure, indicating that there is a conserved subfamily of cuticular col in these nematodes. In this paper, we describe the identification and characterization of a cDNA (Lemmi 5) which corresponds to a cuticular col of the plant-parasitic nematode Meloidogyne incognita. The derived protein structure is very similar to the basic structure of the C. elegans cuticular collagens. Using PCR technology, we have shown the presence of Lemmi 5-related sequences in the genome of Ditylenchus destructor. Our data strongly support the existence of a cuticular col subfamily which is highly conserved in the phylum Nemata.
