Ovarian Tumor Domain-Containing Proteases-Deubiquitylation Enzyme Gene SsCI33130 Involved in the Regulation of Mating/Filamentation and Pathogenicity in Sporisorium scitamineum

Sugarcane is an important sugar crop. Sugarcane smut, caused by Sporisorium scitamineum, is a worldwide sugarcane disease with serious economic losses and lack of effective control measures. Revealing the molecular pathogenesis of S. scitamineum is very helpful to the development of effective prevention and control technology. Deubiquitinase removes ubiquitin molecules from their binding substrates and participates in a variety of physiological activities in eukaryotes. Based on the transcriptome sequencing data of two isolates (Ss16 and Ss47) of S. scitamineum with different pathogenicities, SsCI33130, a gene encoding an OTU1-deubiquitin enzyme, was identified. The positive knockout mutants and complementary mutants of the SsCI33130 gene were successfully obtained through polyethylene glycol-mediated protoplast transformation technology. In order to study the possible function of this gene in pathogenicity, phenotypic comparison of the growth, morphology, abiotic stress, sexual mating, pathogenicity, and gene expression levels of the knockout mutants, complementary mutants, and their wild type strains were conducted. The results demonstrated that the gene had almost no effect on abiotic stress, cell wall integrity, growth, and morphology, but was related to the sexual mating and pathogenicity of S. scitamineum. The sexual mating ability and pathogenicity between the knockout mutants or between the knockout mutant and wild type were more significantly reduced than between the wild types, the complementary mutants, or the wild types and complementary mutants. The sexual mating between the knockout mutants or between the knockout mutant and wild type could be restored by the exogenous addition of small-molecule signaling substances such as 5 mM cyclic adenosine monophosphate (cAMP) or 0.02 mM tryptophol. In addition, during sexual mating, the expression levels of tryptophol and cAMP synthesis-related genes in the knockout mutant combinations were significantly lower than those in the wild type combinations, while the expression levels in the complementary mutant combinations were restored to the level of the wild type. It is speculated that the SsCI33130 gene may be involved in the development of sexual mating and pathogenicity in S. scitamineum by regulating the synthesis of the small-molecule signaling substances (cAMP or tryptophol) required during the sexual mating of S. scitamineum, thereby providing a molecular basis for the study of the pathogenic mechanisms of S. scitamineum.

A Spotlight on Rad52 in Cyanidiophytina (Rhodophyta): A Relic in Algal Heritage

The RADiation sensitive52 (RAD52) protein catalyzes the pairing between two homologous DNA sequences’ double-strand break repair and meiotic recombination, mediating RAD51 loading onto single-stranded DNA ends, and initiating homologous recombination and catalyzing DNA annealing. This article reports the characterization of RAD52 homologs in the thermo-acidophilic Cyanidiophyceae whose genomes have undergone extensive sequencing. Database mining, phylogenetic inference, prediction of protein structure and evaluation of gene expression were performed in order to determine the functionality of the RAD52 protein in Cyanidiophyceae. Its current function in Cyanidiophytina could be related to stress damage response for thriving in hot and acidic environments as well as to the genetic variability of these algae, in which, conversely to extant Rhodophyta, sexual mating was never observed.

Interspecific Gene Exchange as a Driver of Adaptive Evolution in Fungi

Throughout evolutionary history in the kingdom Fungi, taxa have exchanged genetic information among species, as revealed in particular by analyses of genome sequences. In fungi, hybridization can occur by sexual mating or by fusion of vegetative structures giving rise to new species or leaving traces of introgression in the genome. Furthermore, gene exchange can occur by horizontal gene transfer between species and can even include organisms outside the kingdom Fungi. In several cases, interspecific gene exchange has been instrumental in rapid adaptive evolution of fungal species and has notably played a role in the emergence of new pathogens. Here we summarize mechanisms and examples of gene exchange in fungi with a particular focus on the genomic context. We emphasize the need for and potential of applying population genetic approaches to better understand the processes and the impact of interspecific gene exchange in rapid adaptive evolution and species diversification. The broad occurrence of gene exchange among fungal species challenges our species concepts in the kingdom Fungi.

pH Regulates White-Opaque Switching and Sexual Mating in Candida albicans

ABSTRACTAs a successful commensal and pathogen of humans,Candida albicansencounters a wide range of environmental conditions. Among them, ambient pH, which changes frequently and affects many biological processes in this species, is an important factor, and the ability to adapt to pH changes is tightly linked with pathogenesis and morphogenesis. In this study, we report that pH has a profound effect on white-opaque switching and sexual mating inC. albicans. Acidic pH promotes white-to-opaque switching under certain culture conditions but represses sexual mating. The Rim101-mediated pH-sensing pathway is involved in the control of pH-regulated white-opaque switching and the mating response. Phr2 and Rim101 could play a major role in acidic pH-induced opaque cell formation. Despite the fact that the cyclic AMP (cAMP) signaling pathway does not play a major role in pH-regulated white-opaque switching and mating, white and opaque cells of thecyr1/cyr1mutant, which is defective in the production of cAMP, showed distinct growth defects under acidic and alkaline conditions. We further discovered that acidic pH conditions repressed sexual mating due to the failure of activation of the Ste2-mediated α-pheromone response pathway in opaqueacells. The effects of pH changes on phenotypic switching and sexual mating could involve a balance of host adaptation and sexual reproduction inC. albicans.

Fecundity selection theory: concepts and evidence

Fitness results from the optimal balance between survival, mating success and fecundity. The interactions between these three components of fitness vary importantly depending on the selective context, from positive covariation between them, to antagonistic pleiotropic relationships when fitness increases in one reduce fitness of others. Therefore, elucidating the routes through which selection shapes life history and phenotypic adaptations via these fitness components is of primary significance to understand ecological and evolutionary dynamics. However, while the fitness components mediated by natural (survival) and sexual (mating success) selection have extensively been debated from most possible perspectives, fecundity selection remains considerably less studied. Here, we review the theory, evidence and implications of fecundity selection as a driver of sex-specific adaptive evolution. Based on accumulating literature on the life-history, phenotypic and ecological aspects of fecundity, we (i) suggest that ‘fecundity’ is restricted to refer to brood size per reproductive episode, while ‘annual’ and ‘lifetime fecundity’ should not be used interchangeably with ‘fecundity’ as they represent different life history parameters; (ii) provide a generalized redefinition of fecundity selection that encompasses any traits that influence fecundity in any direction (from high to low) and in either sex; (iii) review the (macro)ecological basis of fecundity selection (e.g., ecological pressures that influence predictable spatial variation in fecundity); (iv) suggest that most ecological theories of fecundity selection should be tested in organisms other than birds; (v) argue that the longstanding fecundity selection hypothesis of female-biased sexual size dimorphism (SSD) has gained inconsistent support, that strong fecundity selection does not necessarily drive female-biased SSD, and that this form of SSD can be driven by other selective pressures; and (vi) discuss cases in which fecundity selection operates on males.