Project description:Transcriptome analyses of R5, which is a transformant expressing CpMinus1, originated from NIES-67 of Closterium peracerosum-strigosum-littorale complex
Project description:The Closterium peracerosum-strigosum-littorale (C. psl.) complex is the best characterized charophycean alga with respect to the processes of sexual reproduction. We examined the effect of concanavalin A (Con A) on physiological and ultrastructural changes during the conjugation of the C. psl. complex. Two heterothallic gametangial cells formed a sexual pair as usual; however, the release of gametes was completely blocked by the addition of Con A. Fluorescein isothiocyanate-labeled Con A bound to the outermost layer of the conjugation papillae of paired cells. In the absence of Con A, the disruption of outer cell walls on the conjugation papillae and the secretion of fibrous materials from the conjugation papillae were observed using a transmission electron microscope, but Con A-treated cells did not show these changes. Instead, a highly electron-dense layer was observed in the outermost papillae, and the excess fibrous materials remained at the inside of the layer. These results suggest that an unknown molecule(s) recognized by Con A is essential for the diffusion of fibrous materials at the conjugation papillae, which is an indispensable step for gamete release during conjugation of the C. psl. complex.
Project description:Heterothallic strains of the Closterium peracerosum-strigosum-littorale (C. psl.) complex have two sexes, mating-type plus (mt+) and mating-type minus (mt-). Conjugation between these two sexes is regulated by two sex pheromones, protoplast-release-inducing protein (PR-IP) and PR-IP Inducer, which are produced by mt+ and mt- cells, respectively. PR-IP mediates the release of protoplasts from mt- cells during mating. In this study, we examined the mechanism of action of CpRLP1 (receptor-like protein 1), which was previously identified in a cDNA microarray analysis as one of the PR-IP-inducible genes. Using CRISPR/Cas9 technology, we generated CpRLP1 knockout mutants in mt- cells of the C. psl. complex. When the knockout mt- cells were mixed with wild-type mt+ cells, conjugation was severely reduced. Many cells released protoplasts without pairing, suggesting a loss of synchronization between the two mating partners. Furthermore, the knockout mutants were hypersensitive to PR-IP. We conclude that CpRLP1 is a negative regulator of PR-IP that regulates the timing of protoplast release in conjugating C. psl. cells. As the first report of successful gene knockout in the class Charophyceae, this study provides a basis for research aimed at understanding the ancestral roles of genes that are indispensable for the development of land plants.