Studies on breeding of Porphyra through cell-fusion and cell-line selection

1998 Fiscal Year Final Research Report Summary

• Project/Area Number: 09660205
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: General fisheries
• Research Institution: Nagasaki University
• Principal Investigator: FUJITA Yuji Nagasaki University., Faculty of Fisheries, Professor, 水産学部, 教授 (80039726)
• Co-Investigator(Kenkyū-buntansha): KUWANO Kazuyoshi Nagasaki University, Faculty of Fisheries, Associate Professor (1998), 水産学部, 助教授 (60301363) ; IIMA Masafumi Nagasaki University, Faculty of Environmental Studies, Associate Professor (1997, 環境科学部, 助教授 (80202836)
• Project Period (FY): 1997 – 1998
• Keywords: amino acid resistance / cell-line selection / disease resistance / mutagenesis / Porphyra / Porphyra yezoensis / protoplast fusion / Pythium porphyrae

Research Abstract

Screening of wild species of Porphyra (P.tenuipedalis, P.suburbiculata etc.), green algae (Ulvaceae) revealed different resistance levels among the strains to red rot disease caused by Pythium porphyrae. Intra-generic and inter-phylum protoplast fusion was carried out to transfer the disease resistant traits to the susceptible cultivated P.yezoensis. Of the Intra-generic and inter-phylum protoplast fusion progeny, the transfer and stable inheritance of resistant traits were confirmed in three fusion product progeny of P.yezoensis and P.tenuipedalis. The red rot resistant fusion product strains have also shown resistance to chytrid blight disease, caused by Olpidiopsis sp. The red rot resistant parent and fusion product progeny strains have shown less number of encysted Pythium zoospores and penetration rate in comparison to susceptible cultivated strain. Encystment and primary infection was observed even on other red algal cuticles suggesting the regulation of host-pathogen interaction by the surface galactans on the host surface. Further investigations are required to understand the biochemical basis of this resistance aechanism. The different fusion product progeny strains have displayed almost similar growth rates as the cultivated parent fusion partner. While in comparison, their pigment and free amino acid contents were less than the cultivated parent fusion partner, but were greater than the wild parent fusion partner.
Protoplasts isolated from P.yezoensis were mutagenized with Ethyl methanesulphonate. Mutant cell lines with amino acid resistance to methionine and cystiene were selected. The resistant cell lines have not shown any significant over accumulation any particular or group of free amino acids, in comparison to the untreated lines. While, there were differences in pigmcnt contents, Methionine resistant lines had increased phycoerythrin and phycocyanin contents. The resistant cell lines have also shown higher growth rates than the untreated thalli. This study has revealed a new avenue of using protoplasts for cell line selection.