Antisense Repression of the Medicago truncatula Nodule-Enhanced Sucrose Synthase Leads to a Handicapped Nitrogen Fixation Mirrored by Specific Alterations in the Symbiotic Transcriptome and Metabolome
- 19 October 2007
- journal article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 145 (4), 1600-1618
- https://doi.org/10.1104/pp.107.106955
Abstract
We analyzed the role of the sucrose (Suc) synthase MtSucS1 during nodulation of the model legume Medicago truncatula, integrating data for the developmental, transcriptional, and metabolic processes affected downstream of an impaired Suc cleavage in root nodules. To reduce carbohydrate supply to nodule tissues, transgenic plants expressing a p35S-driven MtSucS1-antisense fusion were constructed. These plants displayed an up to 90% reduction of MtSucS1 proteins in roots and nodules. Phenotypic studies of two independent MtSucS1-reduced lines demonstrated that only under conditions depending on nodulation, these plants appeared to be impaired in above-ground growth. Specifically plant height, shoot weight, leaf development, flowering, as well as seed maturation were reduced, and the efficiency of photosynthesis was affected. Concomitantly, a significantly enhanced root to shoot ratio with a marked increase in root tip numbers was observed. Root nodule formation was found retarded and the impaired nodulation was accompanied by a less efficient nitrogen (N) acquisition. The decreased total N content of MtSucS1-antisense lines and an enhanced carbon to N ratio in roots, nodules, and shoots correlated with the extent of MtSucS1 knockdown. On the level of transcription, effects of an MtSucS1 reduction were evident for genes representing important nodes of the nodule carbon and N metabolism, while metabolite profiling revealed significantly lower levels of amino acids and their derivatives particularly in strongly MtSucS1-reduced nodules. Our results support the model that nodule-enhanced Suc synthase 1 of the model legume M. truncatula is required for the establishment and maintenance of an efficient N-fixing symbiosis.Keywords
This publication has 80 references indexed in Scilit:
- Medicago truncatulaRoot Nodule Proteome Analysis Reveals Differential Plant and Bacteroid Responses to Drought StressPlant Physiology, 2007
- TILLING Mutants of Lotus japonicus Reveal That Nitrogen Assimilation and Fixation Can Occur in the Absence of Nodule-Enhanced Sucrose SynthasePlant Physiology, 2007
- Developmental Genes Have Pleiotropic Effects on Plant Morphology and Source Capacity, Eventually Impacting on Seed Protein Content and Productivity in PeaPlant Physiology, 2007
- Analysis of the sucrose synthase gene family in ArabidopsisThe Plant Journal, 2007
- Medicago truncatula ENOD11: A Novel RPRP-Encoding Early Nodulin Gene Expressed During Mycorrhization in Arbuscule-Containing CellsMolecular Plant-Microbe Interactions®, 2001
- Mutations at therug4locus alter the carbon and nitrogen metabolism of pea plants through an effect on sucrose synthaseThe Plant Journal, 1999
- Enzymes of carbohydrate and amino acid metabolism in developing and mature nodules of white cloverJournal of Experimental Botany, 1997
- NewAgrobacterium helper plasmids for gene transfer to plantsTransgenic Research, 1993
- An Analysis of Seed Development in Pisum sativum. XIII. The Chemical Induction of Storage Product MutantsPlant Breeding, 1990
- Identification and Characterization of Large Plasmids in Rhizobium meliloti using Agarose Gel ElectrophoresisJournal of General Microbiology, 1979