Inflorescence bud protease(s) against dehydrin-like inflorescence bud proteins of Pistacia vera

This paper reports on a proteolytic activity extracted from Pistacia vera L. (pistachio) inflorescence buds, found in male and female tissues. The proteolytic activity reaches a peak at the beginning of bud opening and flowering and is directed against inflorescence bud dehydrin-like proteins of pistachio, IBP32 and IBP27. The effect of protease inhibitors indicated that the protease(s) belong to a serine-protease-like family and are not cysteine, acid or metallo-proteases. The proteolytic activity was strongly inhibited by Nα-p-tosyl-L-lysine chloromethyl ketone and to a lesser extent by N-tosyl-L-phenylalanine chloromethyl ketone, suggesting mainly trypsin-like specificity or broader serine-protease specificity. It is suggested that the proteolytic activity is important in the mobilization of nitrogen reserves stored in the bud storage proteins during dormancy to support the fast-developing inflorescence in spring after bud dormancy break.