Three amino acid permeases, BnAAP1, BnAAP2, and BnAAP6, were identified and characterized. BnAAP1 and BnAAP6 mediated uptake of neutral and acidic amino acids into Xenopus laevis oocytes at the actual apoplastic substrate concentrations.
All three transporters were expressed in leaves and the expression was still detectable during leaf senescence, with BnAAP1 and BnAAP2 mRNA levels increasing from mature to old leaves.
Amino acid permeases are present in senescing leaves of oilseed rape and in some cases are upregulated during senescence.
It is possible that both BnAAP1 and BnAAP2 would become induced at a later stage of silique development as well.
