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 × 10 -16 M). The activity is remarkably thermostable and resistant to different denaturing procedures.

Early event of sexual induction in Volvox: Chemical modification of the extracellular matrix

“…Volvox f2artem.f nagariensis, strain HK 10 (female), was obtained from the Culture Collection of Algae at the University of Texas at Austin (R. C. Starr). Synchronous cultures were grown in Volvox medium (Provasoli and Pintner, 1959) at 28°C in an 8-hr dark/l6-hr light (8000-10,000 lux) cycle (Starr and Jaenicke, 1974).…”

“…Sexual inducer was prepared according to Starr and Jaenicke (1974). Further purification was achieved as previously described (Wenzl et al, 1984).…”

“…This developmental program of Volvox can be changed at will to that of sexual reproduction by addition of a sexual inducer to the growth medium (Starr, 1969;Starr and Jaenicke, 1974). In the female strain, the action of this pheromone is to delay the differentiating cell cleavage until the division from 64 to 128 cells.…”

“…The Volvox carteri pheromone, the "sex inducer" (Starr and Jaenicke, 1974;Gilles et al, 1981) is a 30,000-Da glycoprotein, which is synthesized and secreted by sperm cells. Extremely low concentration of this pheromone (N lo-l6 M) fully trigger sexual development in 1 al ' ' I \ ECU \ I 1…”

Evidence for Autocatalytic Cross-Linking of Hydroxyproline-Rich Glycoproteins during Extracellular Matrix Assembly in Volvox

“…This pheromone is a glycoprotein that triggers the development of males and females at a concentration Ͻ 10 Ϫ 16 M (Starr, 1970;Starr and Jaenicke, 1974;Tschochner et al, 1987;Mages et al, 1988). In particular, the synthesis of some members of the pherophorin family of ECM proteins Sumper 1986b, 1987;Sumper et al, 1993;Godl et al, 1995Godl et al, , 1997 is induced strongly by the pheromone.…”