Poster: Cell walls

Abs # 601: Mannose-adaptation of azuki bean callus involves an inducible enzyme required for sucrose biosynthesis and growth of the cells.

Presenter:	Kato, Aki , aqui1112@hotmail.com
Authors	Kato, Aki  (A)   Inouhe, Masahiro  (A)
Affiliations:	(A): Department of Biology and Earth Sciences,Ehime University

Suspension-cultured cells of azuki bean grow on sucrose, glucose and fructose but not on galactose or mannose. Galactose inhibits sucrose synthesis in these cells but mannose does not (Inouhe and Kato 2003). In the present study we examined the consequences of the presence of mannose on cell growth as a function of sucrose concentrations in both the liquid and solid cultures of azuki bean cells. We also determined the phosphomannose isomerase (PMI) activity in the cells as basis for understanding the conversion of mannose to fructose and sucrose via sugar phosphate pathway. Azuki bean cells incubated in liquid medium containing 1% mannose showed no apparent growth for 10 days and during this period there was a decreased internal sucrose level. This finding suggested that the limited conversion of mannose to sucrose may determine the slow growth rate. By contrast, cells inoculated on agar medium containing mannose proliferated actively after a month of nascent stage and with a concomitant increase in the intracellular sucrose level. This suggested that inducible enzymes such as PMI might be involved in the mannose conversion to sucrose. PMI activity was detected in the mannose-adapted callus cells and the levels increased as a function of culture period. We also found that the callus cells contained an alkaline phosphatase activity. However, similar activity was detected in the cells grown in the sucrose medium. Mannose-adaptation of azuki bean cells thus appeared to employ these and some other path ways for sucrose synthesis.