Decrease in Three Messenger RNA Species Coding for Chloroplast Proteins in Leaves of Barley Infected with Erysiphe graminis f. sp. hordei

Cloned hybridization probes have been used to investigate the effect of infection of susceptible Hordeum vulgare cv Prior by Erysiphe graminis f. sp. hordei on the abundance of host mRNAs coding for the large (LSU) and precursor to the small (SSU) subunits of ribulose 1,5-bisphosphate carboxylase/oxygenase and the rapidly metabolized 32kD thylakoid protein (32kDP). In leaf RNA preparations from control (noninoculated) plants the amount of mRNA for the LSU and SSU declined from 7 to 11 days after sowing, whereas that for the 32kDP increased over this period. Following inoculation at 6 days after sowing, the abundance of each of the mRNA species was significantly reduced below that of controls at 1, 3, and 5 days later. Results indicate that infection causes a rapid and extensive reduction in host mRNA species coding for proteins with important photosynthetic functions.