RESUMO
The interface between the host cell and the microsymbiont is an important zone for development and differentiation during successive stages of the rhizobium-legume symbiosis. Legume root nodule extensins, otherwise known as arabinogalactanprotein-extensin (AGPE) are abundant components of the infection thread matrix. We have characterized the origin and distribution of these glycoproteins at the symbiotic interface of root nodules of symbiotically defective mutants of pea (Pisum sativum L.) using immunogold localization with MAC265 an anti-AGPE monoclonal antibody. For mutants with defective growth of infection threads, the AGPE epitope was abundant in the extracellular matrix surrounding infected host cells in the central infected tissue of the nodule as well as being present in the lumen of Rhizobium-induced infection threads. This suggests a mis-targetting of AGPE as a consequence of abnormal growth of the infection threads. Furthermore, mutants in gene sym33 showed reduced labelling with MAC265, and in infection threads and droplets label was completely absent, a phenomenon not observed in wild-type nodules. This suggests an alteration in the composition of the infection thread matrix for sym33 mutants which may be correlated with the absence of endocytosis of rhizobia into the host cytoplasm.
Assuntos
Glicoproteínas/metabolismo , Mucoproteínas/metabolismo , Mutação , Pisum sativum/metabolismo , Proteínas de Plantas/metabolismo , Rhizobium leguminosarum/fisiologia , Simbiose , Genes de Plantas , Glicoproteínas/genética , Microscopia Confocal , Microscopia Eletrônica , Microscopia de Fluorescência , Mucoproteínas/genética , Fixação de Nitrogênio , Pisum sativum/genética , Pisum sativum/microbiologia , Pisum sativum/ultraestrutura , Proteínas de Plantas/genética , Rhizobium leguminosarum/isolamento & purificação , Rizoma/genética , Rizoma/metabolismo , Rizoma/microbiologia , Rizoma/ultraestrutura , Nódulos Radiculares de Plantas/genética , Nódulos Radiculares de Plantas/metabolismo , Nódulos Radiculares de Plantas/microbiologia , Nódulos Radiculares de Plantas/ultraestruturaRESUMO
Certain characteristics of late noduline gene from pea-Nod6 were investigated as part of works of characterization of higher plant genes taking part in symbiotic nitrogen fixation. The complete 450 b.p. long cDNA was sequenced, it's coding sequence includes the open reading frame. The part of DNA containing the corresponding gene from the genomic clone was also sequenced. The predicted Nod6 amino acid sequence has been analyzed and do not reveal the significant homology with any known protein.
