SYNTHESIS AND PHOSPHORYLATION OF POLLEN PROTEINS DURING THE POLLEN-STIGMA INTERACTION IN SELF-COMPATIBLE BRASSICA-NAPUS L AND SELF-INCOMPATIBLE BRASSICA-OLERACEA L

A technique is described which permits the in vivo study of protein sy nthesis and phosphorylation in the pollen of Brassica spp. during the early stages of the pollen-stigma interaction. Tn Brassica napus and B . oleracea, compatible pollination is followed by a dramatic activatio n of protein synthesis in the pollen involving the synthesis of approx imately 40 proteins. After incompatible pollinations in B. oleracea, v irtually no newly synthesised polypeptides were detected in the pollen except for a small group of high molecular weight proteins which were not normally synthesised during compatible pollinations. Both compati ble and incompatible pollinations were followed by the appearance of n ewly phosphorylated proteins in the pollen; these fell into four disti nct groups. In B. oleracea, the number of phosphorylated proteins and the degree of phosphorylation of individual proteins within the four g roups differed between compatible and incompatible pollinations. One g roup of phosphorylated proteins appeared to correspond with the small group of high molecular weight polypeptides which were synthesised in pollen after incompatible pollinations. These findings are discussed i n the perspective of cell signalling during the pollen-stigma interact ion in Brassica and also in terms of their possible implication in spo rophytic self-incompatibility.