TITLE	High temperature-induced free proline accumulation in Gracilaria tenuistipitata (Rhodophyta)
AUTHOR	Yuan-Chun Chang Institute of Marine Biology, National Sun Yat-sen University, Kaohsiung 80424, Taiwan Tse-Min Lee Institute of Marine Biology, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
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ABSTRACT	The effects of high temperature (35°C) on free proline biosynthesis were studied in a marine red macroalga Gracilaria tenuistipitata var. liui Zhang et Xia. Exposure to 35°C decreased the specific growth rate after 3 days and increased the free proline levels after 2 days, but did not affect the free amino acid levels. Soluble protein levels were constant on exposure to 35°C while those of 25°C-treated thalli increased steadily through the treatment periods. The specific activities of both g-glutamyl kinase (g-GK; EC 2.7.2.11) and glutamate-5-semialdehyde dehydrogenase (GSAd; EC 1.4.1.3) remained unchanged after exposure to 35°C. Upon exposure to 35°C, the specific activity of ornithine d-aminotransferase (d-OAT; EC 2.6.11.3) increased rapidly after 2 days and decreased at Day 5, while that of D1-pyrroline-5-carboxylate reductase (P5CR; EC 1.5.1.2) also increased after 1 day and decreased at Day 4. The increase in d-OAT and P5CR specific activities coincides with the increase in free proline levels. The 35°C induction of free proline accumulation and d-OAT and P5CR activity increase is a light-dependent process. These results suggest that the stimulation of both synthesis (d-OAT and P5CR) and protein proteolysis contributes to the 35°C-induced free proline accumulation in G. tenuistipitata.
KEYWORD	Gracilaria tenuistipitata; GSAd; High temperature; P5CR; Proline; Protein proteolysis; Red alga; d-OAT; g-GK;
ARTICLE INFO	Botanical Bulletin of Academia Sinica, Volume 40 Number 4 October 1999, page 289-294, 6 pages
PUBLISHER	Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Republic of China