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High irradiance responses involving photoreversible multiple photoreceptors as related to photoperiodic induction of cell division in Euglena

Paper ID Volume ID Publish Year Pages File Format Full-Text
31161 44560 2007 12 PDF Available
Title
High irradiance responses involving photoreversible multiple photoreceptors as related to photoperiodic induction of cell division in Euglena
Abstract

Little is known about the photoreceptors involved in the photoperiodism of unicellular organisms, which we elucidated by deriving their action spectra. The flagellated alga Euglena gracilis exhibits photoperiodism, with a long-day response in cell reproduction. The underlying clock is a circadian rhythm with photoinductive capability, peaking at subjective dusk and occurring at the 26th hour in continuous darkness (DD) when transferred from continuous light (LL); it regulates photoinduction, a high-irradiance response (HIR), of a dark-capability of progressing through cell division. We derived the action spectra by irradiating E. gracilis with monochromatic light for 3 h at around the 26th hour; the action maxima occurred at 380, 450–460, 480, 610, 640, 660, 680, and 740 nm. Except for the maximum at 450–460 nm, which was always a major maximum, the maxima greatly depended on the red (R)/far-red (FR) ratio of the prior LL. The high R/FR ratio resulted in a dominant major peak at 640 nm and minor peaks at 480 and 680 nm, whereas the low ratio resulted in dominant major peaks at 610 and 740 nm and minor peaks at 380 and 660 nm; the critical fluence was minimally about 60 mmol m−2. These HIRs resulted from the accumulation of corresponding low-fluence responses (LFRs) because we found that repetition of a 3-min light/dark cycle, with critical fluences of 1 mmol m−2, lasting for 3 h resulted in the same photoinduction as the continuous 3-h irradiation. Moreover, these LFRs expressed photoreversibility. Thus, photoperiodic photoinduction involves Euglena-phytochrome (640 and 740 nm) and blue photoreceptor (460 nm). Although 380, 480, 610, 660, and 680 nm may also represent Euglena-phytochrome, a definite conclusion awaits further study.

Keywords
Cell division cycle; Complementary chromatic adaptation; Circadian; Euglena; End-of-day; Photoperiodism; Phytochrome; Shade avoidance
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High irradiance responses involving photoreversible multiple photoreceptors as related to photoperiodic induction of cell division in Euglena
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology B: Biology - Volume 86, Issue 2, 1 February 2007, Pages 109–120
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us