Abstract
ABSTRACT The stromata of Epichloë fungi are structures covering part of the stem of grasses. Under the fungal layer, still green tissues of the plant survive, although the development of the new leaves is inhibited. Stromata are the places where conidia and ascospores develop. Also, here Botanophila flies dine on mycelium, lay the eggs, defecate, and the larvae develop. The interaction of the three symbionts was analyzed concerning the organisms’ adaptation to understand the differences in physiology and ecology of this microenvironment that support stable symbiosis spreading presently in Europe since the beginning of the XXI century. For analysis of the infrared radiation emitted by stromata, a high-resolution infrared camera FLIR E50 was used. The visualization of stromata temperature profiles was shown in the form of pseudo-colored (false) infrared images. The 13C discrimination was used to characterize photosynthesis of the plant tissue enclosed within the stromata. The stromata had a substantially lower temperature than the green plant tissues. The difference reached ~5.6°C during midday hours, whereas it was smaller in the evening, reaching only ~3.6°C. The mycelium of Epichloë cultivated on agar showed about 2°C lower temperature in comparison to the surrounding. The plant tissues enclosed within the stroma were photosynthetically active, although this activity was of phosphoenolpyruvate carboxylase (PEPC) type and less involved in heat dissipation during the day. The stromata, built by fungal hyphae, on which fungal reproductive structures develop, form a cool shelter. This shelter provides a place for the larvae of Botanophila flies.
Highlights
Members of Epichloë (Clavicipitaceae, Ascomycota) form interactions with many grasses [1]
The leaves inside stromata were still green which was visible on the cross and longitudinal sections and, despite being covered by the mycelium, they were still photosynthetically active, especially within the vascular tissues (red fluorescence of chloroplasts visible in a fluorescence microscope – Figure 1(d))
Numerous stromata were colonized by larvae (Figure 1(e))
Summary
Members of Epichloë (Clavicipitaceae, Ascomycota) form interactions with many grasses [1]. The cryptic stage of the endophyte is controlled by the plant [3] until the specific moment when the balance is somehow destroyed. The fungus changes its behavior and appears as an epiphyte ready for sexual reproduction. Stromata are being formed, initially white and later becoming yellow, when peri thecia with asci and ascospores are produced. Bottleshaped perithecia are formed as a result of fungal crossfertilization. This is possible due to anthomyiid flies of the genus Botanophila [4,5] that are attracted by volatiles produced by the fungus [6] and carry and spread spermatia from different fungal stro mata. Stromata completely or partially pre vent host grasses from flowering and from repro ducing via seeds
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