JXB Advance Access published online on June 1, 2007
Journal of Experimental Botany, doi:10.1093/jxb/erm096
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RESEARCH PAPER |
Functional characterization of LePT4: a phosphate transporter in tomato with mycorrhiza-enhanced expression
1State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China
2Plant Science Department, Weizmann Institute of Science, Rehovot 76100, Israel
3Plant Department, ARO, The Volcani Center, Bet Dagan 50250, Israel
4Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47907, USA
5Institute of Soil, Water and Environmental Science, ARO, The Volcani Center, Bet Dagan 50250, Israel
* To whom correspondence should be addressed. E-mail: avnsil{at}volcani.agri.gov.il
Many plant roots acquire inorganic phosphate (Pi) from soils directly through the root–soil interface via high-affinity Pi transporters and/or through symbiotic associations between the cortical cells and arbuscular mycorrhizal fungi. In tomato, three phosphate transporters (LePT3, LePT4, and LePT5) are up-regulated upon colonization by arbuscular mycorrhizal fungi. In this study, the role of LePT4 in tomato is elucidated by molecular and physiological characterizations of a loss-of-function mutant lept4. In the absence of mycorrhizal infection and under solution-Pi concentrations (Cp) of 0.05 mM and 0.5 mM, the mutant exhibited severe Pi-deficiency symptoms which were associated with significantly lower Pi uptake as compared with that of the wild type. However, at a Cp of 5 mM, lept4 grew better than the wild type. Mycorrhizal infection at a Cp of 0.05 mM resulted in a significant increase in the transcripts of LePT4 in the wild type and a concomitant 2-fold increase in Pi uptake. Although upon mycorrhizal infection, lept4 also exhibited an increased Pi uptake, it was significantly lower than that of the wild type. Under a Cp of 1 mM and in the absence of mycorrhizal infection, LePT4 expression was suppressed in the wild type and a mutation in this gene resulted in a slight reduction in total Pi uptake. These data highlight the pivotal role of LePT4 in mycorrhizal-mediated Pi uptake in tomato, and show that this function may not be fully compensated by other members of the family. Characterization of the mycorrhiza-associated Pi transporter lept4 mutant, along with expression analysis of LePT3, provides evidence for the different routes of mycorrhiza-mediated Pi uptake in plants.
Key words: Glomus intraradices, Lycopersicon esculentum, Micro-Tom, phosphorus acquisition, root/shoot
Received 2 January 2007; Revised 27 March 2007 Accepted 29 March 2007
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