Induction by growth factors of polysaccharide synthases in bean cell suspension cultures.

Suspension cells of bean subcultured into medium that maintains the culture and stimulates cell division but not differentiation brings about an increase in arabinan synthase activity. Subculture into a medium that induces both cell division and xylogenesis brings about in addition an increase in xylan synthase. Both synthases are membrane-bound and are concerned with the formation of neutral pectin or hemicellulose of the cell wall respectively. During the rising phase of the induction of these activities in the appropriate culture medium, the increases in activities were inhibited by either actinomycin D (an inhibitor of transcription) or D-2-(4-methyl-2,6-dinitroanilino)-N-methylpropionamide (an inhibitor of translation). Thus the control for the induction of the enzyme activities involves transcription and possibly translation. Subculture of the cells brought about an increase, probably non-specific, in total membrane-bound translation, as indicated by increased amounts of bound polysomes and incorporation of [35S]methionine into membrane proteins. If the control of the appearance of specific mRNA molecules is partially effected by growth factors then these are probably operative during the period of the cell cycle that is stimulated by subculture and it is probably at this time that the growth factors act to bring about the changes necessary for differentiation.