Fig. 1.

Growth complementation of the ammonium uptake-defective yeast strain 31019b by AtAMT1;4. The triple mep yeast mutant 31019b was transformed with the empty vector p426, p426-AtAMT1;4 or p426-AtAMT1;1. Transformants were pre-cultured for 24 h on YNB medium supplemented with 5 mM arginine. A 1 ml aliquot of a saturated culture was harvested, and resuspended in 1 ml of water. One- to 5-fold dilutions of a 5 μ l aliquot of yeast cell suspension were spotted on YNB medium supplemented with either 5 mM arginine or 1 mM NH₄Cl at pH 6.0.