PLANT SCIENCE: At Root of the Matter

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Science  21 Mar 2008:
Vol. 319, Issue 5870, pp. 1590a
DOI: 10.1126/science.319.5870.1590a

Many plant roots establish a symbiotic relationship with either bacteria or fungi in order to gain access to nutrients, such as fixed nitrogen or phosphate, respectively. Markmann et al. and Gherbi et al. have investigated the evolution of symbiotic relationships between plants and their symbionts and suggest that, on the basis of its nearly universal presence, a single signal transduction component, the leucine-rich-repeat, receptor-like kinase SYMRK, is essential for a host of angiosperms. Genetic knockdown in a member of the cucumber family (Datisca glomerata, a close legume relative) and in the tree Casuarina glauca showed that this protein was essential for bacterial nodulation; furthermore, it also affected fungal symbiosis. Additional investigation revealed that the protein is highly conserved in its ability to mediate these interactions and that this protein does not mediate the exclusive host/symbiont interactions found among species. In addition, three structural SYMRK versions exist among plants with different functional capabilities in the development of root/symbiont interactions, providing an evolutionary hypothesis for the origin of the highly derived nodules in legumes and their close relatives. — LMZ

PLoS Biol. 6, e68; Proc. Natl. Acad. Sci. U.S.A. 105, 10.1073/pnas.0710618105 (2008).

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