Thermal stress responses of a sterile mutant of Ulva pertusa (Chlorophyta)

• Published in: Fisheries science Vol. 67; no. 2; pp. 287 - 294
• Main Authors: Kakinuma, M. (Mie Univ., Tsu (Japan). Faculty of Bioresources), Shibahara, N, Ikeda, H, Maegawa, M, Amano, H
• Format: Journal Article
• Language: English
• Published: Melbourne, Australia Blackwell Science Pty 01.04.2001
• Subjects: CHLOROPHYCEAE; Chlorophyta; GLUTAMATE DEHYDROGENASE; HEAT STRESS; INFERTILITY; isozyme; Marine; MUTANTS; stress response; thermal stress; Ulva; Ulva pertusa; Japan
• ISSN: 0919-9268; 1444-2906
• DOI: 10.1046/j.1444-2906.2001.00229.x

The thermal stress responses of a sterile mutant of the marine alga Ulva pertusa were investigated at 20 deg C and 30 deg C. The amounts of the photosynthetic pigments, beta-carotene, chlorophylls a and b, lutein, neoxanthin, and violaxanthin, were 1.4 - 2.4 times higher in the 30 deg C-cultivated alga than in the 20 deg C-cultivated alga. The free amino acids, asparagine, aspartic acid, glutamine, glutamic acid, glycine, and serine, were abundant in the 20 deg C-cultivated alga, and increased 1.9 - 10.5-fold in response to thermal stress (30 deg C). Total carbon and nitrogen contents also increased in the 30 deg C-cultivated alga. Sodium dodecylsulfate-polyacrylamide gel electrophoretic patterns of total proteins extracted from both temperature-treated algae showed the increases of 20, 25, and 90 kDa proteins in the 30 deg C-cultivated alga. Isozyme assays for 20 enzymes showed a different banding pattern only in the case of glutamate dehydrogenase (GDH). Although it was observed that both temperaturetreated algae possessed NAD sup(+) - and NADP sup(+)-specific GDH, the 30 deg C-cultivated alga had an additional NADP sup(+)-specific GDH (NADP-GDH). These results suggest that NADP-GDH compensates for the thermally induced decreases in nitrogen assimilation efficiency and thereby regulates nitrogen metabolism under conditions of temperature stress.