Transcriptomic analysis of formation and release of monospores in Pyropia yezoensis (Bangiales, Rhodophyta)

Abstract Background Certain red algae (Pyropia yezoensis) of the genus Pyropia can be asexually reproduced by producing monospores, which provides a large number of secondary seeds for marine production. However, the molecular biological mechanism of how algal regulates its own monospores’ formation and release is still unclear, which brings great difficulties and challenges for regulating the yield of seaweed and discovering new strains. Results In this study, we compared and analyzed the data between PY26W' which release a large number of monospores and PY26W which release few monospores by Illumina sequencing platform. The number of DEGs produced by the PY26W' was much higher than that of PY26W, and upregulated genes dominantly in PY26W'. A total of 415 common DEGs were produced between comparison of PY26W and PY26W', which may be involved in formation and release of monospores. All the DEGs were highly enriched in the translation process, ribosome assembly, RNA methylation, assembly of actin and vesicles, intracellular localization of organelles, endocytosis and other biological processes and MAPK signaling pathways. Four DEGs (Contig-21827, Contig-15542, Contig-13390, Trinity-DN39215) were selected for real-time PCR, and the results were highly consistent with the transcriptome sequencing results in both strains, and their expression levels were significant. Further expression analysis indicated that Contig-21827 was abundantly expressed in Pyropia. suborbiculata, Pyropia. chauhanii and PY26W' but not in PY26W and Porphyra haitanensis (WT-8), indicating it plays a key regulatory role in the formation and release of monospores. This gene was further confirmed to be involved in the formation of monospores by analogous conidia formation pathway and was named PyMFG. Conclusion This is the first time to investigate the formation and release of monospores in P. yezoensis from the RNA level. We successfully screened the monospores’ formation gene (PyMFG) of P. yezoensis and the chitinase homologous gene that degraded its cell wall of monosporangia. Which lay a theoretical foundation for the subsequent explanation of the molecular biological mechanism of its formation and release, regulation of seaweed yield and discovery of new seaweed strains.