Journal
PLANT MOLECULAR BIOLOGY
Volume 51, Issue 1, Pages 99-108Publisher
KLUWER ACADEMIC PUBL
DOI: 10.1023/A:1020710222298
Keywords
ammonium transport; legume root nodule; Lotus japonicus; mRNA in situ hybridisation; nitrogen fixation; sub-cellular localisation
Categories
Ask authors/readers for more resources
Two related families of ammonium transporters have been identified and partially characterised in plants in the past; the AMT1 and AMT2 families. Most attention has focused on the larger of the two families, the AMT1 family, which contains members that are likely to fulfil different, possibly overlapping physiological roles in plants, including uptake of ammonium from the soil. The possible physiological functions of AMT2 proteins are less clear. Lack of data on cellular and tissue location of gene expression, and the intracellular location of proteins limit our understanding of the physiological role of all AMT proteins. We have cloned the first AMT2 family member from a legume, LjAMT2; 1 of Lotus japonicus, and demonstrated that it functions as an ammonium transporter by complementing a yeast mutant defective in ammonium uptake. However, like AtAMT2 from Arabidopsis, and unlike AMT1 transporters from several plant species, LjAMT2; 1 was unable to transport methylammonium. The LjAMT2; 1 gene was found to be expressed constitutively throughout Lotus plants. In situ RNA hybridisation revealed LjAMT2; 1 expression in all major tissues of nodules. Transient expression of LjAMT2; 1-GFP fusion protein in plant cells indicated that the transporter is located on the plasma membrane. In view of the fact that nodules derive ammonium internally, rather than from the soil, the results implicate LjAMT2; 1 in the recovery of ammonium lost from nodule cells by efflux. A similar role may be fulfilled in other organs, especially leaves, which liberate ammonium during normal metabolism.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available