Light-induced conidiation of Trichoderma spp. strains is accompanied by development-dependent changes in the Ca 2+ binding to cell walls.

The effect of light on the binding of Ca ²⁺ to mycelia and to cell walls isolated from aerial mycelia of three strains of Trichoderma spp. was studied. Two independent methods were used to measure the total Ca ²⁺ content in mycelia and the Ca ²⁺ bound to cell walls isolated from aerial mycelia. The results of these methods showed that the light-induced formation and maturation of conidia in Trichoderma spp. is accompanied by increased Ca ²⁺ deposition in mycelia and cell walls. Moreover, the cultivation of Trichoderma atroviride F-534 in the presence of ⁴⁵ Ca ²⁺ under circadian illumination showed that radioactivity was exclusively localized in the light-induced conidial rings of aerial mycelia. The fluorescence microscopy of chlortetracycline-stained mycelia showed that the major fraction of Ca ²⁺ was accumulated in conidia and fructification structures, or some intracellular compartments in T. atroviride F-534 grown under circadian illumination, while only a limited amount of Ca ²⁺ was associated with hyphal surfaces. In addition, the study of ⁴⁵ Ca ²⁺ binding to cell walls revealed that T. atroviride F-534 displays both increased ⁴⁵ Ca ²⁺ binding capacity and elevated affinity to ⁴⁵ Ca ²⁺ binding upon illumination. The results indicate that conidia formation and (or) maturation is associated with changes in Ca ²⁺ homeostasis.