sentence: In Solanaceae , a stylar glycoprotein with ribonuclease activity acts as the female S-determinant of GSI , because it is abundantly expressed in the style of self-incompatible Nicotiana alata and co-segregates with the observed S-phenotypes ( Bredemeijer and Blaas , 1981 ; Anderson et al ., 1986 ; McClure et al ., 1989 ) .