Effects of Helminthosporium maydis T toxin on the ATPase activity of maize root membrane preparations and its sensitivity to diethylstilbestrol

The effects of Helminthosporium maydis race T toxin (HMT) on K+-stimulated and DES-sensitive ATPase activity of membrane preparations from susceptible and resistant maize roots were investigated. HMT slightly but significantly inhibited K+-stimulated ATPase activity of the preparations from the susceptible, but not of those from resistant tissue, thus confirming previously reported data. A much clearer effect of HMT was the protection of ATPase activity against the inhibiting action of DES. This effect appeared much greater for the susceptible than for the resistant preparations and was still evident even on deoxycholate-solubilised ATPase preparations. These data suggest a direct interaction between HMT and an ATPase complex presumably located at the plasmalemma.