Acclimation of chlorophyll biosynthetic reactions to temperature stress in cucumber (Cucumis sativus L.) |
| |
Authors: | Arun Kumar Tewari Baishnab Charan Tripathy |
| |
Institution: | (1) School of Life Sciences, Jawaharlal Nehru University, New Delhi 110067, India, IN |
| |
Abstract: | The adaptive responses of the greening process of plants to temperature stress were studied in cucumber (Cucumis sativus L. cv. Poinsette) seedlings grown at ambient (25 °C), low (7 °C) and high (42 °C) temperatures. Plastids isolated from these
seedlings were incubated at different temperatures and the net syntheses of various tetrapyrroles were monitored. In plastids
isolated from control seedlings grown at 25 °C, the optimum temperature for synthesis of Mg-protoporphyrin IX monoester or
protochlorophyllide was 35 °C. Temperature maxima for Mg-protoporphyrin IX monoester and protochlorophyllide syntheses were
shifted to 30 °C in chill-stressed seedlings. The net synthesis of total tetrapyrroles was severely reduced in heat-stressed
seedlings and the optimum temperature for Mg-protoporphyrin IX monoester or protochlorophyllide synthesis shifted slightly
towards higher temperatures, i.e. a broader peak was observed. To further study the temperature acclimation of seedlings with
respect to the greening process, tetrapyrrole biosynthesis was monitored at 25 °C after pre-heating the plastids (28–70 °C)
isolated from control, chill- and heat-stressed seedlings. In comparison to 28 °C-pre-heated plastids the percent inhibition
of protochlorophyllide synthesis in 40 °C-pre-heated plastids was higher than for the control (25 °C-grown) in chill-stressed
seedlings and lower than for the control in heat-stressed seedlings. Maximum synthesis of total tetrapyrroles and protoporphyrin
IX was observed when chloroplasts were heated at 50 °C, which was probably due to heat-induced activation of the enzymes involved
in protoporphyrin IX synthesis. Prominent shoulders towards lower or higher temperatures were seen in chill-stressed or heat-stressed
seedlings, respectively. The shift in optimum temperature for tetrapyrrole biosynthesis in chill- and heat-stressed seedlings
was probably due to acclimation of membranes possibly undergoing desaturation or saturation of membrane lipids. Proteins synthesized
in response to temperature-stress may also play an important role in conferring stress-tolerance in plants.
Received: 8 October 1998 / Accepted: 19 November 1998 |
| |
Keywords: | :Cucumis (temperature stress) Chill and heat stress Chlorophyll biosynthesis Protochlorophyllide Protoporphyrin IX Temperature stress |
本文献已被 SpringerLink 等数据库收录! |
|