Light-induced conidiation ofTrichodermaspp. strains is accompanied by development-dependent changes in the Ca2+binding to cell walls

Abstract

The effect of light on the binding of Ca2+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 Ca2+content in mycelia and the Ca2+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 Ca2+deposition in mycelia and cell walls. Moreover, the cultivation of Trichoderma atroviride F-534 in the presence of45Ca2+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 Ca2+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 Ca2+was associated with hyphal surfaces. In addition, the study of45Ca2+binding to cell walls revealed that T. atroviride F-534 displays both increased45Ca2+binding capacity and elevated affinity to45Ca2+binding upon illumination. The results indicate that conidia formation and (or) maturation is associated with changes in Ca2+homeostasis.