Transcriptomic analysis under ethylene precursor treatment uncovers the regulation of gene expression linked to sexual reproduction in the dioecious red alga Pyropia pseudolinearis

The marine red algal genus Pyropia, class Bangiophyceae, includes dioecious and monoecious species; however, the molecular mechanisms underlying control of their sexual reproduction are still poorly understood. In the present study, we demonstrated that application of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), promoted the formation of spermatangia and parthenosporangia in male and female gametophytes, respectively, of the dioecious species Pyropia pseudolinearis. In addition, we determined expression profiles of ACC-responsive genes in the gametophytes during sexual reproduction using RNA-Seq and quantitative real-time PCR (qRT-PCR). Genes involved in the regulation of cell division and cell wall organization, such as high-mobility group (PpHMG) and glycosyltransferase family (PpGT14), were found to be upregulated in male and female gametophytes treated with ACC. In addition, the relatively rapid ACC-response of the vesicular-trafficking-related genes, flotillin (PpFLOT), charged multivesicular body protein 5 (PpCHMP5), and peptidase family S8 (PpS8) was shown to occur during male and female sexual reproduction. Expression levels of these six genes in the monoecious species P. yezoensis, which are homologs to ACC-responsive genes in P. pseudolinearis, also increased in gametophytes treated with ACC. These findings could provide new insights into the ACC-regulation of the sexual life cycle in Pyropia species.