APINOD · Functions of antioxidants and peroxide in legume nodule development
FP6 — Marie Curie Actions (Human Resources and Mobility)
- Duration
- 2005-06-01 → 2006-05-31
- EU contribution
- €40,000
- Participants
- 1
- Scheme
- ERG
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Results in brief
Final Activity Report Summary - APINOD (Functions of antioxidants and peroxide in legume nodule development)
Legume nodules are symbiotic structures formed by the molecular interaction between rhizobia and plant roots. Nodules contain antioxidant enzymes and metabolites to protect N2 fixation from reactive oxygen species. Superoxide dismutases (SODs) are metalloenzymes that play a primary role in the protection against oxidative stress in plants and other organisms. We have characterised four SOD genes in Lotus japonicus and have analysed their expression in roots and four developmental stages of nodules. The expression of cytosolic CuZnSOD, at the mRNA, protein, and enzyme activity levels, decreases with nodule age, and the protein is localised in the dividing cells and infection threads of emergent nodules, and in cytosol of the infected cells of young nodules. The mitochondrial MnSOD gene was downregulated, whereas the bacteroidal MnSOD gene had maximal protein and enzyme activity levels in older nodules. Two additional genes, encoding plastidic (FeSOD1) and cytosolic (FeSOD2) FeSOD isoforms, were identified and mapped. The genes are located in different chromosomes and show differential expression. The FeSOD1 mRNA level did not change during nodule development, whereas FeSOD2 was upregulated. The distinct expression patterns of the SOD genes may reflect different regulatory mechanisms of the enzyme activities during nodule ontogeny. In particular, at the mRNA and activity levels, the virtual loss of cytosolic CuZnSOD in mature and old nodules, concomitant with the induction of FeSOD2, suggest that the two enzymes may functionally compensate each other in the cytosol at the late stages of nodule development.
Data: CORDIS, © European Union
Project objective
Biological nitrogen fixation represents an economical and environmentally-friendly alternative to chemical fertilization. Anaspect of the rhizobia-legume symbiosis with important implications in other fields of plant biology is the molecular basis thatdiff erentiate symbiosis and pathogenesis. In plants under pathogen attack, there is a rapid and transient increase in theproduction of reactive oxygen species (oxidative burst"). In contrast, during the symbiotic interaction, rhizobia may escape orinhibit the plant's defense response possibly due to bacterial Nod factors and, possibly, polysaccharides. However, hydrogenperoxide has been detected in the infection threads and nodule apoplast, suggesting that it is involved in several steps ofnodulation, such as the growth of cell walls and infection threads. Our previous studies have also shown that nodules containhigh levels of all three superoxide dismutases (CuZnSOD, FeSOD, MnSOD) and, based on co-localization and inhibitorstudies, we have proposed that CuZnSO D may be a source of hydrogen peroxide in nodules. The general objective of thisthree-year project is to study in detail the functions of SODs in nodule development. Using Medicago sativa and Lotuscorniculatus to compare indeterminate and determinate nodul ation, we will determine: (1) the regulatory mechanisms ofexpression for the three sod genes in nodules; (2) the spatio-temporal patterns of activity for the sod promoters; and (3) theeffect of suppression of SOD expression in nodules. To accomplish these specific objectives, a multidisciplinary and innovativeapproach and state-of-the-art techniques will be used. Methodologies include gene-specific quantification of transcripts forSODs and other antioxidant enzymes by real time RT-PCR, cytochemical localiza tion of superoxide and hydrogen peroxide,fusion constructs between promoters and reporter genes, transgenic roots and nodules ("hairy root" system), and genesil'"
Original text from CORDIS.
Participants
- CONSEJO SUPERIOR DE INVESTIGACIONES CIENTIFICAS · MADRIDCoordinatorSpain
Links
Data: CORDIS, © European Union