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Hterologous complementation of yeast mutants has enabled the isolation of genes encoding several families of amino acid transporters. Among them, NTR1 codes for a membrane protein with weak histidine transport activity. However, at the sequence level, NTR1 is related to rather non-specific oligopeptide transporters from a variety of species including Arabidopsis and to the Arabidopsis nitrate transporter CHL1. A yeast mutant deficient in oligopeptide transport was constructed allowing to show that NTR1 functions as a high affinity, low specificity peptide transporter. In siliques NTR1-expression is restricted to the embryo, implicating a role in the nourishment of the developing seed.
Rentsch et al. (Mon,) studied this question.