Purification and characterization of the hormone initiating sexual morphogenesis in Volvox carteri f. nagariensis Iyengar

Abstract

In Volvox carteri f. nagariensis male spheroids secrete into the medium a sexual hormone which controls the initiation of the developmental pathway leading to the formation of sexual embryos. In the absence of the hormone asexual embryos are formed. Analysis of the highly purified hormone indicates that it is a glycoprotein of 27,500-30,000 daltons, composed of one peptide chain, which has a typical composition except for a relatively low content of tryptophan. The glycosidic moiety, which accounts for about 45% of the weight of the molecule, consists of pentoses, hexoses, and amino hexoses. In the bioassay the highly purified hormone stimulates 100% formation of sexual embryos at a concentration of 10(-10) g/liter and 14.4% sexual embryos at 10(-11) g/liter (3 x 10(-16) M). The activity is remarkably thermostable and resistant to different denaturing procedures.