Patrick Still - Nitrogen Deprivation Stimulates Symbiotic Gland Development in Gunnera manicata.

Document created by Patrick Still on Aug 22, 2014
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  Wan-Ling Chiu, Gerald A. Peters,   Germain Levieille, Patrick C. Still, Sarah Cousins, Bruce   Osborne, and Jeff Elhai (2003). Nitrogen Deprivation Stimulates   Symbiotic Gland Development in Gunnera manicata.   Plant Physiology 139: 224-230.


  Gunnera is the only genus of angiosperms known to host   cyanobacteria and the only group of land plants that hosts   cyanobacteria intracellularly. Motile filaments of cyanobacteria,   known as hormogonia, colonize Gunnera plants through cells in the   plant's specialized stem glands. It is commonly held that Gunnera   plants always possess functional glands for symbiosis. We found,   however, that stem gland development did not occur when   Gunnera manicata plants were grown on nitrogen   (N)-replete medium but, rather, was initiated at predetermined   positions when plants were deprived of combined N. While N status   was the main determinant for gland development, an exogenous   carbon source (sucrose) accelerated the process. Furthermore, a   high level of sucrose stimulated the formation of callus-like   tissue in place of the gland under N-replete conditions.   Treatment of plants with the auxin transport inhibitor   1-naphthylphthalamic acid prevented gland development on   N-limited medium, most likely by preventing resource reallocation   from leaves to the stem. Optimized conditions were found for in   vitro establishment of the Nostoc-Gunnera symbiosis by   inoculating mature glands with hormogonia from Nostoc   punctiforme, a cyanobacterium strain for which the full   genome sequence is available. In contrast to uninoculated plants,   G. manicata plants colonized by N. punctiforme  were able to continue their growth on N-limited medium.   Understanding the nature of the Gunnera plant's unusual   adaptation to an N-limited environment may shed light on the   evolution of plant-cyanobacterium symbioses and may suggest a   route to establish productive associations between N-fixing   cyanobacteria and crop plants.

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