Sequence of the Gonium pectorale Mating Locus Reveals a Complex and Dynamic History of Changes in Volvocine Algal Mating Haplotypes

Sex-determining regions (SDRs) or mating-type (MT) loci in two sequenced volvocine algal species, Chlamydomonas reinhardtii and Volvox carteri, exhibit major differences in size, structure, gene content, and gametolog differentiation. Understanding the origin of these differences requires investigation of MT loci from related species. Here, we determined the sequences of the minus and plus MT haplotypes of the isogamous 16-celled volvocine alga, Gonium pectorale, which is more closely related to the multicellular V. carteri than to C. reinhardtii. Compared to C. reinhardtii MT, G. pectorale MT is moderately larger in size, and has a less complex structure, with only two major syntenic blocs of collinear gametologs. However, the gametolog content of G. pectorale MT has more overlap with that of V. carteri MT than with C. reinhardtii MT, while the allelic divergence between gametologs in G. pectorale is even lower than that in C. reinhardtii. Three key sex-related genes are conserved in G. pectorale MT: GpMID and GpMTD1 in MT–, and GpFUS1 in MT+. GpFUS1 protein exhibited specific localization at the plus-gametic mating structure, indicating a conserved function in fertilization. Our results suggest that the G. pectorale–V. carteri common ancestral MT experienced at least one major reformation after the split from C. reinhardtii, and that the V. carteri ancestral MT underwent a subsequent expansion and loss of recombination after the divergence from G. pectorale. These data begin to polarize important changes that occurred in volvocine MT loci, and highlight the potential for discontinuous and dynamic evolution in SDRs.

Investigating the Smuts: Common Cues, Signaling Pathways, and the Role of MAT in Dimorphic Switching and Pathogenesis

The corn smut fungus Ustilago maydis serves as a model species for studying fungal dimorphism and its role in phytopathogenic development. The pathogen has two growth phases: a saprobic yeast phase and a pathogenic filamentous phase. Dimorphic transition of U. maydis involves complex processes of signal perception, mating, and cellular reprogramming. Recent advances in improvement of reference genomes, high-throughput sequencing and molecular genetics studies have been expanding research in this field. However, the biology of other non-model species is frequently overlooked. This leads to uncertainty regarding how much of what is known in U. maydis is applicable to other dimorphic fungi. In this review, we will discuss dimorphic fungi in the aspects of physiology, reproductive biology, genomics, and molecular genetics. We also perform comparative analyses between U. maydis and other fungi in Ustilaginomycotina, the subphylum to which U. maydis belongs. We find that lipid/hydrophobicity is a potential common cue for dimorphic transition in plant-associated dimorphic fungi. However, genomic profiles alone are not adequate to explain dimorphism across different fungi.

Whole-Genome Sequencing and Fine Map Analysis of Pholiota nameko

Pholiota nameko (T. Ito) S. Ito and S. Imai is an emerging wild mushroom species belonging to the genus Pholiota. Its unique brown-yellow appearance and significant biological activity have garnered increasing attention in recent years. However, there is a relative lack of research on the biological characteristics and genetics of P. nameko, which greatly limits the potential for an in-depth exploration of this mushroom in the research fields of molecular breeding and evolutionary biology. This study aimed to address that gap by employing Illumina and Nanopore sequencing technologies to perform whole-genome sequencing, de novo assembly, and annotation analysis of the P. nameko ZZ1 strain. Utilizing bioinformatics methods, we conducted a comprehensive analysis of the genomic characteristics of this strain and successfully identified candidate genes associated with its mating type, carbohydrate-active enzymes, virulence factors, pan-genome, and drug resistance functions. The genome of P. nameko ZZ1 is 24.58 Mb in size and comprises 33 contigs, with a contig N50 of 2.11 Mb. A hylogenetic analysis further elucidated the genetic relationship between P. nameko and other Pholiota, revealing a high degree of collinearity between P. nameko and ZZ1. In our enzyme analysis, we identified 246 enzymes in the ZZ1 genome, including 68 key carbohydrate-active enzymes (CAZymes), and predicted the presence of 11 laccases, highlighting the strain's strong potential for cellulose degradation. We conducted a pan-genomic analysis of five closely related strains of Pholiota, yielding extensive genomic information. Among these, there were 2608 core genes, accounting for 21.35% of the total genes, and 135 dispensable genes, highlighting significant genetic diversity among Pholiota and further confirming the value of pan-genomic analysis in uncovering species diversity. Notably, while we successfully identified the A-mating-type locus, composed of the homeodomain protein genes HD1 and HD2 in ZZ1, we were unable to obtain the B-mating-type locus due to technical limitations, preventing us from acquiring the pheromone receptor of the B-mating-type. We plan to supplement these data in future studies and explore the potential impact of the B-mating-type locus on the current findings. In summary, the genome data of ZZ1 presented in this study are not only valuable resources for understanding the genetic basis of this species, but also serve as a crucial foundation for subsequent genome-assisted breeding, research into cultivation technology, and the exploration of its nutritional and potential medicinal value.