MtSWEET11, a Nodule-Specific Sucrose Transporter of Medicago truncatula
Igor S Kryvoruchko1, Senjuti Sinharoy1, Ivone Torres-Jerez1
1Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, OK (I.S.K., S.S., I.T.-J., C.I.P., M.K.U.); Department of Plant Biology, Carnegie Institution of Science, Stanford, CA 94305 (D.S., W.B.F.); Department of Cell and Developmental Biology, John Innes Centre, Norwich, NR4 7UH, United Kingdom (D.G., J.M.); and Division of Plant & Soil Sciences, West Virginia University, Morgantown, WV 26506 (V.A.B.).
Abstract:
Optimization of nitrogen fixation by rhizobia in legumes is a key area of research for sustainable agriculture. Symbiotic nitrogen fixation (SNF) occurs in specialized organs called nodules and depends on a steady supply of carbon to both plant and bacterial cells. Here we report the functional characterization of a nodule-specific Suc transporter, MtSWEET11 from Medicago truncatula MtSWEET11 belongs to a clade of plant SWEET proteins that are capable of transporting Suc and play critical roles in pathogen susceptibility. When expressed in mammalian cells, MtSWEET11 transported sucrose (Suc) but not glucose (Glc). The MtSWEET11 gene was found to be expressed in infected root hair cells, and in the meristem, invasion zone, and vasculature of nodules. Expression of an MtSWEET11-GFP fusion protein in nodules resulted in green fluorescence associated with the plasma membrane of uninfected cells and infection thread and symbiosome membranes of infected cells. Two independent Tnt1-insertion sweet11 mutants were uncompromised in SNF Therefore, although MtSWEET11 appears to be involved in Suc distribution within nodules, it is not crucial for SNF, probably because other Suc transporters can fulfill its role(s).
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