Figure 1.
Phylogeny of Fsy1 transporters.
Phylogeny based on the amino acid sequence of all Fsy1 homologues identified in the Pezizomycotina and the Saccharomycotina. For species possessing multiple Fsy1 homologues, the numbers ‘1’, ‘2’ or ‘3’ are added to the species designation. Background colors refer to the supra-generic taxa to which each species belongs. White numbers before species names denote the number of introns found in each FSY1 gene. Putative HGT events discussed in the text are numbered sequentially in boxes: yellow, HGT events supported by topology tests; white, putative HGT events not supported by topology tests; grey, HGT events that cannot be tested. FSY1 genes functionally characterized in this study or in previous studies are indicated by red and white stars, respectively. The tree is rooted at the midpoint. Bootstrap support values are depicted in tree branches (>50%) as given in the key. Species names are abbreviated as given in Table S1.
Figure 2.
Gene content and organization in FSY1 loci in Saccharomycetes.
Chromosomal regions (chr) or scaffolds (sc) encompassing FSY1 gene are depicted by grey bars for most of the Saccharomycetes species represented in the species tree (of which a subsection is shown on the left). Pink bars represent syntenic regions where FSY1 gene is absent (e.g. is Candida tanzawaensis and Candida tenuis) and those in green indicate instances where FSY1 gene was likely acquired by HGT. The FSY1 gene is shown as a strongly outlined red arrow in the center, denoting transcriptional orientation. Within each clade (highlighted by a different background color), orthologous genes are depicted in the same color. Non-syntenic genes are colored white and those in black represent tRNA or Ty elements. The end of a chromosome is indicated by a bracket next to a gene (e.g. see FSY1 location in S. uvarum). Partial FSY1 gene sequences are indicated with an asterisk. Gene accession numbers are only shown for FSY1 or immediate flanking genes as they appear in their respective genome databases. The remaining labels are as in Figures 1. Species names are abbreviated as given in Table S1.
Figure 3.
Species phylogeny and FSY1 ancestral state reconstruction.
Phylogeny based on the concatenated amino acid sequences of six RNA polymerase subunits (see methods) from all the species in the Ascomycota surveyed for the presence of Fsy1 and for which whole genome data was available. Four species from the Basidiomycota were used as outgroup. Background colors refer to different supra-generic taxa (Family in the Saccharomycotina and Class in the Pezizomycotina). The label “WGD” indicates species that underwent Whole Genome Duplication. Tree branches depicted in black denote cases where the Fsy1 gene is present in the extant species and red lines indicate branches that lack an Fsy1 gene. Values on tree branches denote the likelihood of Fsy1 being present in the ancestors and are reported as proportional likelihoods, as determined by ancestral state reconstruction. For branches with no values, the likelihood is >0.95 for the presence or absence of Fsy1, as indicated by the color of the lines in the derived branches. Bootstrap support values are depicted in tree branches (>50%) as given in the key. The remaining labels are as in Figure 1. Species names are abbreviated as given in Table S1.
Figure 4.
Gene content and organization in FSY1 genomic region in the Eurotiales.
(A) Subsection of the tree depicted in Figure 3 underlining possible events leading to the extant distribution of FSY1 genes in species of Eurotiales. The three types of FSY1 genes are depicted as squares and colored according to their most likely origin as shown in the key. The most likely point of acquisition of each of the genes is indicated by a colored square on the respective tree branch. FSY1 gene losses (possibly due to xenolog gene displacement – XGD) are indicated by red crosses. ‘I’, ‘II’, ‘III’ and ‘IV’ represent different lineages within the Eurotiales. (B) Comparative organization of the cognate FSY1 locus in Aspergilli species represented in the tree shown in A. Genes are shown as white arrows denoting the direction of transcription and orthologs are connected with vertical bars of the same color. FSY1 orthologs in the center are connected by red bars. (C) Comparative organization of the genomic region encompassing the FSY1 gene presumably acquired from the Sordariomycetes by HGT (event 14 in Figure 1) to the MRCA of lineage ‘IV’. In (D) the same is shown for FSY1 genes acquired by HGT from the Saccharomycetes clade. Only syntenic genes (orthologs) are connected by vertical bars. Species names are abbreviated as in Table S1.
Figure 5.
Conservation of Fsy1 function across a broad phylogenetic range.
Biochemical properties of Fsy1 homologs of various origins were expressed as sole hexose transporter in a S. cerevisiae hxt-null. (A) Fsy1 activity assessed by measurement of the alkalinisation elicited by the addition (marked by the arrows) of fructose (red) or sorbose (blue) to unbuffered cell suspensions of the hxt-null strain expressing various Fsy1 homologs, as indicated. Glucose (grey) fails to elicit a pH change in all cases. (B) Growth of the hxt-null strain expressing Fsy1 homologs on medium containing fructose, glucose or maltose as sole carbon and energy source, as indicated. (C) Estimated Km values for D-[U-14C]fructose uptake mediated by various Fsy1 homologs, including those reported in previous studies. Species names are abbreviated as in Table S1. S. pastorianus (Sacpas) is a hybrid species harbouring the FSY1 gene from parental species S. eubayanus (Saceub).