BRUSSELS, July 2 - Euro zone producer prices edged lower by 0.4 percent in May and rose 1.3 percent on a year-on-year basis, the European Union statistics office said on Wednesday. The figures were in line with analysts' expectations. Data for April was revised to show a month-on-month fall of 0.5 percent compared with an originally reported 0.4 percent fall. The annual gain in April was unchanged at 1.7 percent. Energy prices were again a major factor in the figures for the euro zone in May, falling 1.8 percent on a monthly basis and rising 1.7 percent year-on-year.//