Open AccessGlycine-Rich Proteins Encoded by a Nodule-Specific Gene Family Are Implicated in Different Stages of Symbiotic Nodule Development in Medicago Spp.
Author(s) -
Zoltán Kevei,
JoséMaría Vinardell,
G. B. Kiss,
Ádám Kondorosi,
Éva Kondorosi
Publication year - 2002
Publication title -
molecular plant-microbe interactions
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.565
H-Index - 153
eISSN - 1943-7706
pISSN - 0894-0282
DOI - 10.1094/mpmi.2002.15.9.922
Subject(s) - biology , sinorhizobium meliloti , medicago truncatula , nodule (geology) , gene , root nodule , rhizobium , mutant , microbiology and biotechnology , glycine , gene expression , genetics , symbiosis , amino acid , bacteria , paleontology
Four genes encoding small proteins with significantly high glycine content have been identified from root nodules of Medicago sativa. All of these proteins as well as their Medicago truncatula homologues carried an amino terminal signal peptide and a glycine-rich carboxy terminal domain. All except nodGRP3 lacked the characteristic repeat structure described for cell wall and stress response-related glycinerich proteins (GRP). Expression of these GRP genes was undetectable in flower, leaf, stem, and hypocotyl cells, whereas expression was highly induced during root nodule development, suggesting that GRP genes act as nodulins. Moreover, none of these nodule-expressed GRP genes were activated by hormones or stress treatments, which are inducers of many other GRPs. In Rhizobium-free spontaneous nodules and in nodules induced by a noninfective mutant strain of Sinorhizobium meliloti, all these genes were repressed, while they were induced in Fix¯ nodules, unaffected in bacterial infection, but halted in bacteroid differentiation. These results demonstrated that bacterial infection but not bacteroid differentiation is required for the induction of the nodule-specific GRP genes. Differences in kinetics and localization of gene activation as well as in the primary structure of proteins suggest nonredundant roles for these GRPs in nodule organogenesis.