Uphill Shifts of Fungal Fruiting Due to Climate Change at the Polar Urals

Due to the ongoing climatic changes in the Arctic, the ranges of many plants and animal species are rising higher into the mountains, into the treeline; however, such studies are rare for fungi. The 60-year fruiting dynamics of 66 species of Agaricomycetous macrofungi has been studied along the altitudinal transect located on the slope of Slantsevaya Mountain (Polar Urals, Russia). It has been found that the three basic trophic groups (mycorrhizal, saprobes on litter and soil, and saprobes on wood) fruit higher in the mountains. Additionally, for most of the studied species, a tendency towards upward displacement of fruiting was revealed. The rise in fruiting for saprobes on litter and soil was the most obvious. Mycorrhizal fungi associated with woody plants showed the least uplifting effect. Fungal species that were characterized by fruiting higher up the mountainside half a century ago show stronger upward shifts compared to species previously bearing fruit only at the mountain foot. Probably, such a reaction of the aboveground mycobiota is similar to the processes occurring in the soil, which are associated with an active increase in the decomposition rate of the litter, an increase in the depth of permafrost thawing, and a significant redistribution of the soil water balance. On the other hand, the rise of fungi is associated with an increase of plant biomass in the middle and upper parts, which are the most important sources of fungal nutrition.

Nitrogen, Iron and Zinc Acquisition: Key Nutrients to Aspergillus fumigatus Virulence

Aspergillus fumigatus is a ubiquitous soil decomposer and an opportunistic pathogen that is characterized by its large metabolic machinery for acquiring nutrients from media. Lately, an ever-increasing number of genes involved in fungal nutrition has been associated with its virulence. Of these, nitrogen, iron, and zinc metabolism-related genes are particularly noteworthy, since 78% of them have a direct implication in virulence. In this review, we describe the sensing, uptake and regulation process of the acquisition of these nutrients, the connections between pathways and the virulence-implicated genes. Nevertheless, only 40% of the genes mentioned in this review have been assayed for roles in virulence, leaving a wide field of knowledge that remains uncertain and might offer new therapeutic and diagnostic targets.

Protocorm-Supporting Fungi Are Retained in Roots of Mature Tipularia discolor Orchids as Mycorrhizal Fungal Diversity Increases

Mycorrhizal fungi are critical to understanding the distribution patterns of many plants, but they are especially important for orchids. Some orchids may change the mycorrhizal fungi they use through their lives, either in response to changes in abiotic or biotic conditions, or as a result of ontogenetic changes that alter the orchid’s need for fungal nutrition. The temperate terrestrial orchid Tipularia discolor germinates only on decomposing wood, but often persists well after the wood has completely decomposed and has been incorporated into the soil. We used PCR and Sanger sequencing to ask: (1) Do mature T. discolor retain protocorm fungi or are protocorm and adult mycorrhizal fungi mutually exclusive? (2) Are protocorm fungi limited to areas with decomposing wood? (3) Does the abundance of protocorm fungi in the substrate differ between decomposing wood and bare soil? We found that T. discolor retained protocorm fungi into maturity, regardless of whether they were growing in persistent decomposing wood or soil. Protocorm fungi were not restricted to decomposing wood but were more common and abundant in it. We conclude that the mycorrhizal fungi associated with T. discolor change during the ontogeny of individuals. These results highlight the importance of assessing protocorm fungi, in addition to mycorrhizal fungi associating with adult orchids, to understand the conditions needed for orchid germination, growth, and reproduction.

Structure-specific regulation of nutrient absorption, metabolism and transfer in arbuscular mycorrhizal fungi

Arbuscular mycorrhizal fungi (AMF) establish symbiotic relationships with most land plants, mainly for the purpose of nutrient exchange. Many studies have revealed the regulation of absorption, metabolism, and transfer of nutrients in AMF and the genes involved in these processes. However, the spatial regulation of the genes among the structures comprising each developmental stage are not well understood. Here, we demonstrate the structure-specific transcriptome of the model AMF species, Rhizophagus irregularis. We performed an ultra-low input RNA-seq analysis, SMART-seq2, comparing five extraradical structures, germ tubes, runner hyphae, branched absorbing structures, immature spores, and mature spores. In addition, we reanalyzed the recently reported RNA-seq data comparing intraradical hyphae and arbuscules. Our analyses captured the distinct features of each structure and revealed the structure-specific expression patterns of genes related to absorption, metabolism, and transfer of nutrients. Of note, the transcriptional profiles suggest the distinct functions of branched absorbing structures in nutrient absorption. These findings provide a comprehensive dataset to advance our understanding of the transcriptional dynamics of fungal nutrition in this symbiotic system.