Blue Light Regulation in Plants and Microorganisms

Authored by: Aba Losi , Wolfgang Gärtner

CRC Handbook of Organic Photochemistry and Photobiology

Print publication date:  March  2012
Online publication date:  March  2012

Print ISBN: 9781439899335
eBook ISBN: 9781466561250
Adobe ISBN:


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Following many centuries of observation of plant orientation toward light [1], we have only quite recently become aware that phototropism is regulated by blue-light (BL) sensing photoreceptor proteins that were accordingly coined as phototropins (phot) [2]. Many more physiological processes have been ascribed to the presence of BL photoreceptors in plants, including stomata opening, chloroplast movements, leaf expansion, solar tracking, and circadian rhythms regulation [1,3,4]. The long-sought plant photoreceptors for BL, which represents a ubiquitous, subtle, and dominating (vide infra) environmental factor for the living world, presently comprise cryptochromes (Cry) [5,6], phot, Zeitlupe (ZTL), LOV Kelch Protein 2 (LKP2), and Flavin-binding Kelch F-box1 (FKF1) proteins [4]. All these photoreceptors host riboflavin (RB, vitamin B2) derivatives as chromophores, bound within defined protein domains or subdomains: a photolyase (PL)-like domain in Cry binds flavin-adenine dinucleotide (FAD) into an all-helix subdomain; the light, oxygen, voltage (LOV) domain of phot and ZTL/LKP2/FKF1, forming a small α/β unit, binds flavin mononucleotide (FMN) [2]. The blue-light sensing using FAD (BLUF) domain, the third type of flavin (FL)-based photosensing unit, is solely found in Euglenoids and Bacteria and binds FAD. Cry and the phot-related, so-called LOV proteins appear to be ubiquitous, being widespread in prokaryotes, fungi, and lower plants [7,8]. Cry are present also in animals [6,9,10], whereas LOV proteins are the sole FL-based BL sensors occurring also in Archaea (see also Section 53.2) [8].

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