Predicting the impacts of climate change, soils and vegetation types on the geographic distribution of Polyporus umbellatus in China.

Polyporus umbellatus is a fungus that has been used medically as a diuretic for thousands of years in China. To evaluate the impacts of climatic change on the distribution of P. umbellatus, we selected the annual mean air temperature, isothermality, minimum temperature of the coldest month, annual temperature range, annual precipitation and precipitation seasonality and used observations from the 2000s and simulated values from two future periods (2041 to 2060 and 2061 to 2080) to build an ensemble model (EM); then, we developed a comprehensive habitat suitability model by integrating soil and vegetation conditions into the EM to assess the distribution of suitable P. umbellatus habitats across China in the 2000s and the two future periods. Our results show that annual precipitation and annual mean air temperature together largely determine the distribution of P. umbellatus and those suitable P. umbellatus habitats generally occur in areas with an optimal annual precipitation of approximately 1000 mm and an optimal annual mean air temperature of approximately 13 °C. In other words, P. umbellatus requires a humid and cool environment for growth. In addition, brown soils with a granular structure and low acidity are more suitable for P. umbellatus. Furthermore, we have observed that the distribution of P. umbellatus is usually associated with the presence of coniferous, mixed coniferous, and broad-leaved forests, suggesting that these vegetation types are suitable habitats for P. umbellatus. In the future, annual precipitation and annual mean air temperature will continue to increase, consequently increasing the availability of habitats suitable for P. umbellatus in northeastern and southwestern China but likely leading to a degradation of suitable P. umbellatus habitats in central China.

Phylogenetic constrains on Polyporus umbellatus-Armillaria associations.

It has been well established that some Armillaria species are symbionts of Polyporus umbellatus, However, little is known about the evolutionary history of P. umbellatus-Armillaria associations. In this research, we used an analysis based on the strength of the phylogenetic signal to investigate P. umbellatus-Armillaria associations in 57 sclerotial samples across 11 provinces of China. We isolated Armillaria strains from the invasion cavity inside the sclerotia of P. umbellatus and then phylogenetically analyzed these Armillaria isolates. We also tested the effect of P. umbellatus and Armillaria phylogenies on the P. umbellatus-Armillaria associations. We isolated forty-seven Armillaria strains from 26 P. umbellatus sclerotial samples. All Armillaria isolates were classified into the 5 phylogenetic lineages found in China except for one singleton. Among the 5 phylogenetic lineages, one lineage (lineage 8) was recognized by delimitation of an uncertain phylogenetic lineage in previous study. Results of simple Mantel test implied that phylogenetically related P. umbellatus populations tend to interact with phylogenetically related Armillaria species. Phylogenetic network analyses revealed that the interaction between P. umbellatus and Armillaria is significantly influenced by the phylogenetic relationships between the Armillaria species.

Involvement of Ca(2+) channel signalling in sclerotial formation of Polyporus umbellatus.

Growth and morphogenesis transformation in Polyporus umbellatus were examined in the presence of various pharmacological compounds, to investigate signal transduction pathways that influence the development of sclerotia. Both the calcium channel blocker nifedipine and the calcium ionophor A23187 reduced sclerotial production in P. umbellatus; four classes of Ca(2+) signal agent-including calcium chelators, calcium channel blockers, calcium ionophors and calmodulin inhibitors-were further studied. Among them, EGTA and BAPTA, as calcium chelators, exhibited a complete inhibitory effect on sclerotial formation, among the levels tested. Calcium channel blockers and calcium ionophors at the concentrations used in this study could not eliminate sclerotia formation completely, but did greatly reduce sclerotial production. Notoginsenoside in dosages >250 microg/ml produced a significant negative effect on mycelial growth, and it prevented sclerotial formation entirely at a dosage of 500 microg/ml; no other drug influenced vegetative growth at all. The calcium ionophor A23187 did not decrease sclerotial mean weight at low doses (20 nM); at higher doses (200 nM), however, sclerotial development was significantly reduced, albeit not completely halted. The CaM inhibitors (W-7 and chlorpromazine) could each completely stop sclerotial formation. Using Fluo-3/AM as the indicator of cytosolic free calcium, the Ca(2+) content in the cytoplasm was found to have decreased significantly when hyphae were treated with different drugs, and there was no active Ca(2+) signal in the sclerotial mycelium. In general, the results suggest that Ca(2+) signal transduction may play an important role in sclerotial formation in P. umbellatus.