Project description:Diverse sex determination mechanisms have been reported in eukaryotes, but little is known about the genetic pathways leading to sex determination in red algae. Sex-specific genes that could be involved in sex determination and sexual differentiation were investigated in a red alga Bostrychia moritziana by analyzing the transcriptomes of various phases including males, females and tetrasporophytes. Sex-dominantly-expressed genes which shows >10 fold difference between sexes were isolated using comparative RNA-seq analysis. We found 19 gene homologues, 10 from males and 9 from females, that were found only in one sex in genomic amplification. This suggests that these divergent homologues are on non-recombining, possibly different, chromosomes in their respective sexes. Most of the sex-specific genes are involved in important cellular processes including chromosome segregation, nucleo-cytoplasmic protein shuttling or tRNA modification. Quantitative PCR analysis also showed that some sex-specific genes were differently regulated during critical events of sexual reproduction like fertilization and carposporophyte development. We could also localize the expression of a male-specific gene in spermatia before and after gamete binding using RNA in situ hybridization. Another set of transcripts were found that were sex-dominantly-expressed, but not sex-specific. 19 out of 39 sex-dominantly-expressed transcripts were annotated to transposable elements, but none of them was sex-specific. Our results suggest that sexual differentiation in B. moritziana may be achieved by multi-level regulation of cellular processes, both from genes present only in one sex and differential expression of shared genes.
Project description:This study presents a chemotaxonomic investigation of the genus Bostrychia through the quantitation of the major mycosporine-like amino acids (MAAs). The presence of some cryptic species had been suggested in the B. moritziana/B. radicans complex and MAA-profiling in respective samples revealed different chemotypes within this species complex. Another possibly polyphyletic species is Bostrychia simpliciuscula; previous molecular phylogenetic analyses showed four genetic lineages within this species, one of which was recently distinguished as a new species. Phytochemical profiling of those samples used for DNA analyses revealed four different chemotypes, corresponding to the above four lineages and it supports the re-circumscription of the other three B. simpliciuscula lineages. Therefore, mycosporine-like amino acids are considered as suitable chemotaxonomic markers for the reassessment of the classification of B. simpliciuscula. The determination of the MAA patterns in these algae was possible after developing and validating a suitable high-performance liquid chromatography-diode array detector (HPLC-DAD) method.
