RHIZOBIUM LIPOOLIGOSACCHARIDES RESCUE A CARROT SOMATIC EMBRYO MUTANT

At a nonpermissive temperature, somatic embryos of the temperature-sen sitive (ts) carrot cell mutant ts11 only proceed beyond the globular e mbryo stage in the presence of medium conditioned by wild-type embryos . The causative component in the conditioned medium has previously bee n identified as a 32-kD acidic endochitinase. In search of a function for this enzyme in plant embryogenesis, several compounds that contain oligomers of N-acetylglucosamine were tested for their ability to pro mote ts11 embryo formation. Of these compounds, only the Rhizobium lip ooligosaccharides or nodulation (Nod) factors were found to be effecti ve in rescuing the formation of ts11 embryos. These results suggest th at N-acetylglucosamine-containing lipooligosaccharides from bacterial origin can mimic the effect of the carrot endochitinase. This endochit inase may therefore be involved in the generation of plant analogs of the Rhizobium Nod factors.