RAPID INHIBITION OF PROTEIN HISTIDINE PHOSPHORYLATION BY UV-IRRADIATION IN XANTHOMONAS-ORYZAE PV ORYZAE

Exposure of Xanthomonas oryzae pv. oryzae tells to 254 nm UV radiation resulted in an alteration of protein phosphorylation. Labelling of th e phosphohistidine-containing proteins with molecular masses of 81 and 32 kDa, named p81 and p32, was rapidly reduced following UV irradiati on in the early exponential cells, but the decrease was not detected i n mid-exponential cells. Mitomycin C, a DNA replication inhibitor, and rifampicin, a drug generally used to inhibit RNA synthesis and DNA re plication, were also found to reduce the histidyl phosphorylation. How ever, this alteration of protein phosphorylation was not hindered by c hloramphenicol treatment. A possible role for these histidyl phosphopr oteins in sensing UV light is proposed.