Carrageenan oligosaccharides enhance stress-induced microspore embryogenesis in Brassica oleracea var. italica

Embryogenic induction in cultures of isolated microspores is a stress-depen dent process, which can be triggered by heat shock, sucrose or nitrogen sta rvation or by anti-microtubular drugs. As they are known to mimic biotic st ress, oligosaccharides were tested as an alternative sourer of compounds to induce microspore embryogenesis in Brassica oleracea var, italica. Among t he eight oligosaccharide series that were investigated and the correspondin g polysaccharides, namely pectin, alginate. fucan. laminarin, agar and kapp a-, t-, and lambda -carrageenans, only the carrageenan oligomers displayed significant effects on microspore induction. When supplied in combination t o heat stress, they markedly enhanced the final yields of microspore-derive d embryos, with a two-fold increase in the most reactive treatment, i,e. in the presence of h-carrageenan oligosaccharides. A 30 min treatment was eno ugh to stimulate embryogenesis. and two optimal concentrations were observe d, 170 nM and 34 muM. (C) 2001 Elsevier Science Ireland Ltd. All rights res erved.