Journal
PLANT CELL AND ENVIRONMENT
Volume 33, Issue 12, Pages 2112-2120Publisher
WILEY-BLACKWELL
DOI: 10.1111/j.1365-3040.2010.02209.x
Keywords
boron; exopolysaccharide; legume-rhizobia symbiosis; matrix glycoproteins; nitrogen fixation; pectins; root nodule extensin
Categories
Funding
- Ministerio de Educacion y Ciencia [BIO2008-05736-CO2-01]
- Comunidad de Madrid
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The capacity to bind to biomolecules is considered to be the basis for any physiological role of boron (B). Legume arabinogalactan protein-extensin (AGPE), a major component of the infection thread matrix of legume nodules is a potential B-ligand. Therefore, its role in infection threads development was investigated in Pisum sativum grown under B deficiency. Using the AGPE-specific antibody MAC265, immunochemical analysis revealed that a 175 kDa MAC265 antigen was abundant in +B but much weaker in -B nodule extracts. A B-dependent complex involving AGPE and rhamnogalacturonan II (RGII) could be co-purified using anti-RGII antiserum. Following fractionation of -B nodules, MAC265 antigens were mostly associated with the bacterial pellet. Immunogold staining confirmed that AGPE was closely associated with the surface of rhizobia in the lumen of threads in -B nodules whereas in +B nodules, AGPE was separated from the bacterial surface by a sheath of capsular polysaccharide. Interestingly, colonies of rhizobia grown in free-living culture without B developed low capsule production. Therefore, we propose that B could be important for apical growth of infection threads by strengthening thread wall through a B-dependent AGPE-RGII interaction and by promoting bacterial advance through a B-dependent production of a stable rhizobial capsule that prevents AGPE attachment.
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