Characterizing plasma membrane H+-ATPase in two varieties of coffee leaf (Coffea arabica L.) and its interaction with an elicitor fraction from the orange rust fungus (H. vastatrix Berk and Br.) race II.

Early intercellular signaling in Coffea arabica L.-Hemileia vastatrix host-pathogen interaction was studied, using inside-out plasma membrane from two varieties of coffee leaf and a fungal fraction to determine the plant's biochemical responses. Microsomal pellets (100,000 x g) from the susceptible (Caturra) and resistant (Colombia) coffee leaf varieties were purified by partitioning in two-polymer DEX (6.3% w/w) and PEG (6.3% w/w) system aqueous phase. Fungal material was obtained from orange rust Hemileia vastatrix Berk and Br. race II urediospore germ tubes. Plasma membrane vesicles were preferentially localized to PEG phase, as indicated by its enzyme marker distribution. Both H(+)-ATPase activities displayed similar kinetic and biochemical characteristics, comparable to those described for P-type ATPases. Several enzymes may play pivotal roles in plants regarding early interaction with fungal elicitors. Studies of fungal fractions' effects on H(+)-ATPase and both varieties' proton pumping activities were thus carried out. Concentration as low as 0.1 Gluc eq. ml(-1) fungal fraction induced specific inhibition of H(+)-ATPase and the resistant variety's proton pumping activities. The present work describes characterizing the H(+)-ATPase plasma membrane from two Coffea arabica L. varieties (Caturra and Colombia) for the first time and the race specific inhibitory effect of a crude fungal fraction on both H(+)-ATPase and the resistant variety's proton pumping activities.