XVI International Botanical Congess

Here we propose a model for how ATP regulates the channel conductance of multi-drug resistance (MDR) channels. In this model ATP gradients between the inside and outside of cells regulate the efflux of substrates through MDR channels. This model is supported by data from yeast and plants. Using Arabidopsis transformed to express an endogenous MDR channel called P-glycoprotein (Pgp), we observe increased accumulation of ATP on leaf surfaces. The same Arabidopsis Pgp expressed in a yeast system causes the steady-state level of extracellular ATP to double. We have documented a drug-resistant state in plants, and this resistant state is easily scored both in transgenic and mutagenized lines. We have identified a second component of a multicomponent MDR system which is as effective as Pgp in promoting drug resistance.