CONVERGENT PATHWAYS FOR LIPOCHITOOLIGOSACCHARIDE AND AUXIN SIGNALING IN TOBACCO CELLS

Lipochitooligosaccharides (LCOs) are a novel class of plant growth reg ulators that activate in tobacco protoplasts the expression of AXI1, a gene implicated in auxin signaling. Transient assays with a chimeric P-AXI-GUS expression plasmid revealed that the N-octadecenoylated mono saccharide GlcN has all structural requirements for a biological activ e glycolipid, whereas the inactive N-acylated GalN epimer inhibits LCO action. Specific inhibition of LCO and auxin action shows that both s ignals are transduced within the tobacco cell via separate pathways th at converge at or before AXI1 transcription. Cytokinin is suggested to be a common effector of LCO and auxin signaling. We also show that ac tivation of AXI1 correlates with growth factor-induced cell division.