Obesity Risk Gene TMEM18 Encodes a Sequence-Specific DNA-Binding Protein

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Alphapartitiviruses of Heterobasidion wood decay fungi affect each other’s transmission and host growth

Abstract Heterobasidion spp. root rot fungi are highly destructive forest pathogens of the northern boreal forests, and are known to host a diverse community of partitiviruses. The transmission of these mycoviruses occurs horizontally among host strains via mycelial anastomoses. We revealed using dual cultures that virus transmission rates are affected by pre-existing virus infections among two strains of H. annosum. The transmission efficacy of mycovirus HetPV15-pa1 to a pre-infected host was elevated from zero to 50% by the presence of HetPV13-an1, and a double infection of these viruses in the donor resulted in an overall transmission rate of 90% to a partitivirus-free recipient. On contrary, pre-existing virus infections of two closely related strains of HetPV11 hindered each other’s transmission, but had unexpectedly dissimilar effects on the transmission of more distantly related viruses. The co-infection of HetPV13-an1 and HetPV15-pa1 significantly reduced host growth, whereas double infections including HetPV11 strains had variable effects. Moreover, the results showed that RdRp transcripts are generally more abundant than capsid protein (CP) transcripts and the four different virus strains express unique transcripts ratios of RdRp and CP. Taken together, the results show that the interplay between co-infecting viruses and their host is extremely complex and highly unpredictable

Phenotypic recovery of a Heterobasidion isolate infected by a debilitation-associated virus is related to altered host gene expression and reduced virus titer

Abstract The fungal genus Heterobasidion includes forest pathogenic species hosting a diverse group of partitiviruses. They include the host debilitating Heterobasidion partitivirus 13 strain an1 (HetPV13‐an1), which was originally observed in a slowly growing H. annosum strain 94233. In this study, a relatively fast-growing sector strain 94233‐RC3 was isolated from a highly debilitated mycelial culture of 94233, and its gene expression and virus transcript quantities as well as the genomic sequence of HetPV13‐an1 were examined. The sequence of HetPV13‐an1 genome in 94233‐RC3 was identical to that in the original 94233, and thus not the reason for the partial phenotypic recovery. According to RNA-seq analysis, the HetPV13‐an1 infected 94233‐RC3 transcribed eight genes differently from the partitivirus-free 94233‐32D. Three of these genes were downregulated and five upregulated. The number of differentially expressed genes was considerably lower and the changes in their expression were small compared to those of the highly debilitated original strain 94233 with the exception of the most highly upregulated ones, and therefore viral effects on the host transcriptome correlated with the degree of the virus‐caused debilitation. The amounts of RdRp and CP transcripts of HetPV13‐an1 were considerably lower in 94233‐RC3 and also in 94233 strain infected by a closely related mildly debilitating virus HetPV13‐an2, suggesting that the virus titer would have a role in determining the effect of HetPV13 viruses on their hosts