A unique life cycle transition in the red seaweed Pyropia yezoensis depends on apospory

Abstract

Plant life cycles consist of two temporally separated stages: a haploid gametophyte and a diploid sporophyte. In plants employing a haploid–diploid sexual life cycle, the transition from sporophyte to gametophyte generally depends on meiosis. However, previous work has shown that in the red seaweed Pyropia yezoensis , this transition is independent of meiosis, though how and when it occurs is unknown. Here, we explored this question using transcriptomic profiling of P . yezoensis gametophytes, sporophytes, and conchosporangia parasitically produced on sporophytes. We identify a knotted-like homeobox gene that is predominately expressed in the conchosporangium and may determine its identity. We also find that spore-like single cells isolated from the conchosporangium develop directly into gametophytes, indicating that the gametophyte identity is established before the release of conchospores and prior to the onset of meiosis. Based on our findings, we propose a triphasic life cycle for P . yezoensis involving production of gametophytes by apospory.

Health Functionality and Quality Control of Laver (Porphyra, Pyropia): Current Issues and Future Perspectives as an Edible Seaweed

“…Advances in applied transcriptome analysis include identification of housekeeping genes involved in internal control processes [157]. With respect to the life cycle, previous studies focused on characterization of the evolutionary aspects of the distinct stages [158,159], development of applied technologies including the designation of biomarkers [160], and treatments affecting the regulation of gene expression linked to reproductive processes [161]. A major focus for genomic research has been the interpretation and/or comparative analysis of transcriptomic data relating to the responses of laver species to abiotic stress [162,163], principally environmental conditions such as high temperature [164][165][166], repeated desiccation-rehydration [167,168], and hypersalinity [169].…”

Difference in Nitrogen Starvation-Inducible Expression Patterns among Phylogenetically Diverse Ammonium Transporter Genes in the Red Seaweed <i>Pyropia yezoensis</i>

“…Based on the functional annotation in our P. yezoensis transcriptome analysis [31], we identified six unigenes (CL1839, CL3739, Unigene15210, CL1882. Con-tig5, CL1882.…”

Gamete expression of TALE class HD genes activates the diploid sporophyte program in Marchantia polymorpha

“…Life cycles of eukaryotes alternate between haploid and diploid phases, initiated by meiosis and gamete fusion, respectively. Expression of paralogous homeodomain (HD) genes in the two gametes and the subsequent heterodimerization of the respective proteins in the zygote direct the haploid-to-diploid transition in gene expression in phylogenetically diverse eukaryotes, including the ascomycete fungus Saccharomyces cerevisiae ( Goutte and Johnson, 1988 ; Herskowitz, 1989 ), the basidiomycete fungi Coprinopsis cinerea and Ustilago maydis ( Gillissen et al, 1992 ; Hull et al, 2005 ; Kues et al, 1992 ; Spit et al, 1998 , Urban, 1996 ), the Amoebozoa Dictyostelium discoideum ( Hedgethorne et al, 2017 ), the brown alga Ectocarpus ( Arun et al, 2019 ), the red alga Pyropia yezoensis ( Mikami et al, 2019 ), and the unicellular chlorophyte alga Chlamydomonas reinhardtii ( Ferris and Goodenough, 1987 ; Lee et al, 2008 ; Nishimura et al, 2012 ; Zhao et al, 2001 ). This broad phylogenetic distribution suggests this was an ancestral function of HD genes (reviewed by Bowman et al, 2016b ).…”