INDOLE-3-ACETIC-ACID ELICITS CA2-DEPENDENT CALLOSE SYNTHESIS IN THE PROTONEMA OF FUNARIA-HYGROMETRICA()

The present report provides an account of the possible involvement of auxin (Indole-3-acetic acid) in callose biosynthesis, prior to cell di fferentiation in moss protonema (chloronema to caulonema), which is pr imarily an auxin-controlled event. Chloronema tip cells in Funaria hyg rometrica respond to IAA (5 x 10(-5) mol/L) treatment by localised cal lose synthesis in the basal region of the cell before changing the pat tern of cell growth and subsequent division as caulonema. A qualitativ e comparison of the callose accumulation response in the wild strain c hloronema filaments, with those of the two auxin mutants, indicates a correlation between auxin sensitivity of the specific strain and the e xtent of callose accumulation along the cross wall and the adjacent la teral wall of the apical cells. The percentage of responding tip cells in the three strains varied between 65 and 80 %. Least callose accumu lation is observed in the auxin-insensitive mutant 86.1. The present i nvestigations further suggest an important role of auxin-induced influ x of Ca2+ in callose synthesis, although it does not seem to be the so le factor responsible for the regulation of this process.