Survival analyses of symbionts isolated from Endocarpon pusillum Hedwig to desiccation and starvation stress

Abstract

This work deals with the survival analyses of the symbionts isolated from the lichen E. pusillum under desiccation and starvation stress. The mycobiont of the symbionts was under the desiccation in combination with starvation stress, and under starvation stress alone as well. The phycobiont of the symbionts was under desiccation stress alone. The experiments were detected by means of the biomass size, weight and cell density, deformity of the hyphae and cells, and metabolic activity through SEM (scanning electron microscopy), TEM (transmission electron microscopy), FM (fluorescence microscopy), spectrophotometry, and FCM (flow cytometry). The results show that the mycobiont can survive for seven months under desiccation stress in combination with starvation stress, and for eight months under starvation stress alone. The phycobiont can survive for two months under desiccation stress. It can provide a scientific basis for further research of the reproduction biology of lichens and arid desert biocarpet engineering to fix sand and carbon. One of the central challenges of adversity-resistance biology is to understand the responses and adaptations of desert species to arid conditions. A lichen is a life-support system composed of a specific fungus (mycobiont) and a corresponding alga (phycobiont) or a cyanobacterium (cyanobiont) in an unique symbiotic relationship. "Their unique symbiotic relationship with algae has enabled these fungi to colonize and flourish in a wide range of habitats from the Antarctic continent to the rain forests of the tropics. Their ecological success in so many types of habitats depends on a number of unique structural and functional adaptations that are only now beginning to be generally appreciated by mycologists and microbiologists" [1]. Lichens are some of the most drought-resistant organisms; this characteristic has been extensively studied. In particular, levels of resistance to desiccation have been assessed using photosynthesis or respiration as indicators. Most of lichens are able to survive desiccation for several months [2−4], and a few species can survive for more than a year [4,5]. In reviewing previous studies, Lange [4] concluded that there was a general correlation between water conditions within the habitat and desiccation tolerance, i.e., the drier the habitat, the greater the desiccation tolerance of the lichen.Although the length of the desiccation period that lichens can survive is well documented, this information is still limited for isolated symbionts. Ahmadjian and Hale [6] reviewed the previous studies of desiccation resistance of isolated symbionts, and indicated that the isolated mycobionts could survive desiccation for five weeks (three species) or six weeks (seven species), while the isolated phycobionts could survive for six weeks (13 species) or 41 weeks (two

Impact of inorganic nitrogen additions on microbes in biological soil crusts

“…This result is distinct from the studies by Porras-Alfaro et al (2011) using the clone library method, Abed et al (2013) using pyrosequencing and Bates et al (2012) using DGGE fingerprinting, in which the order Pleosporales were widespread and frequently dominant, while this order exhibited a relatively low abundance in our work (1.4%). Nevertheless, it is not surprising that Endocarpon contribute the major fungal components in Endocarpon Pusillum-dominated crusts when we examined both the free-living fungi and lichenized fungi specific to our crusts, as Endocarpon Pusillum is a dominant lichen group that is widespread in the Tengger desert (Zhang and Wei, 2011) and our research region mainly comprises Endocarpon Pusillum-dominated crusts.…”

Genome characteristics reveal the impact of lichenization on lichen-forming fungus Endocarpon pusillum Hedwig (Verrucariales, Ascomycota)

“…The systematics and physiology of E. pusillum (Figure 1) have been studied well. The mycobiont E. pusillum exhibits much stronger desiccation-tolerant than other non-lichenized fungi as it can survive for 7 months under desiccation stress in combination with starvation stress [26]. Although a large number of fungal genomes have been published, no lichen-forming is included, and only two mitochondrial genomes from lichen-forming fungi ( Peltigera membranacea and Peltigera malacea ) and a transcriptome from the lichen Cladonia rangiferina have been reported until now [27,28].…”

“…B. The isolated mycobiont and phycobiont [26]. C. Cross section of a perithecium with hymenial algal cells inside.…”

Comparative transcriptome analysis of the lichen-forming fungus Endocarpon pusillum elucidates its drought adaptation mechanisms

“…However, in drought resistance, the mycobiont partner seems to be the main contributor in lichens [1921], probably due to the fact that within lichens, the photobionts are housed by the fungal tissues, which effectively protect their photosynthetic partners from desert climate. For example, a previous study indicated that, separately, the lichen-forming fungus Endocarpon pusillum has a much stronger drought resistant ability than its algal partner Diplosphaera chodatii [22]. Therefore, to understand the mechanisms of drought resistance in lichens, it is reasonable to focus on the fungal partner.…”