CHANGES IN PROTEINS AND PEROXIDASES INDUCED BY COMPATIBLE POLLINATIONIN THE OVARY OF NICOTIANA-TABACUM-L AHEAD OF THE ADVANCING POLLEN TUBES

Proteins and peroxidases produced by the ovules and placenta of tobacc o (Nicotiana tabacum L.) in response to compatible pollination were an alyzed by two-dimensional polyacrylamide,eel electrophoresis and by en zyme staining in flat-bed native isoelectric focusing gels. For two-di mensional gels, ovaries were sampled at 36 h after pollination, at whi ch time pollen tubes have penetrated much of the length of the style b ut have not yet entered the ovary. At least 11 major proteins from pol linated ovaries had no detectable counterparts in unpollinated ovaries . These showed a range of molecular mass and pi. For peroxidase isozym e assays, ovaries were sampled at 0, 12, 24, 36 and 48 h after pollina tion. At 45-50 h, pollen tubes were beginning to enter the top of the ovary but could still be separated from the ovules and placenta during sampling. Ovules and placentae from unpollinated pistils showed only one form of peroxidase, whereas those from pollinated pistils showed a dditional isozymes at pH 5.4 and pH 10.0. Both new isozymes increased in staining intensity over the first 36 h after pollination. At 48 h, however, the acidic peroxidase had continued to increase, while the ba sic component had declined so as to be barely detectable. The observat ions are discussed in relation to accumulating evidence that some form of pollination-induced signal reaches the ovary ahead of the advancin g pollen tubes. The nature of this signal and possible involvement of peroxidases are also briefly discussed.