AMINO-ACID-TRANSPORT IN PLANTS

Amino acids are transported between different organs through both xyle m and phloem. This redistribution of nitrogen and carbon requires the activity of amino acid transporters in the plasma membrane. in additio n, amino acids can be taken up directly by the roots. Amino acid trans port has been well characterized in the yeast Saccharomyces cerevisiae , and functional complementation has served as an excellent tool for i dentifying and characterizing amino acid transporters from plants. The transporters from yeast and plants are related and can be grouped int o two large superfamilies. Based on substrate specificity and affinity , as well as expression patterns in plants, different functions have b een assigned to some of the individual transporters. Plant mutants for amino acid transporter genes are now being used to study the physiolo gical functions of many of the cloned genes.