Distribution of activated calmodulin in the chloronema tip cells of the moss Funaria hygrometrica

Auxin (indole-3-acetic acid) regulates caulonema differentiation as a result of gradual transitional events in the chloronema tip cells in moss protonema. This auxin action in the moss Funaria hygrometrica involves a rapid influx of calcium ions from the extracellular medium. This investigation demonstrates spatial and temporal changes in calmodulin (CaM) activation (formation of Ca2+-CaM complex) in the chloronema tip cells subjected to auxin treatment. Photomicroscopic localisation of the fluorescence (excitation at 365nm and emission of 397nm) from the tricomplex of Ca2+-CaM with trifluoperazine (TFP, a blocker of Ca2+-CaM action) shows a tip to base (tip high) gradient of Ca2+-CaM in the chloronema tip cells. Comparison of Ca2+-CaM-TFP fluorescence over time in the chloronema tip cells of wild type Funaria with the response in an auxin overproducer mutant (86.1) and an auxin deficient mutant (87.13) reveals the involvement of auxin in calmodulin activation as a rapid response prior to cell differentiation.