Shedding (blue) light on algal gene expression
- Aba Losi*,† and
- Wolfgang Gärtner‡
- *Department of Physics, University of Parma, Viale G. P. Usberti 7A, 43100 Parma, Italy; and
- ‡Max Planck Institute for Bioinorganic Chemistry, Stiftstrasse 34-36, D-45470 Mülheim, Germany
Light in the blue region of the spectrum [blue light (BL), 400–480 nm] is an ubiquitous environmental signal. BL can penetrate marine water to a depth greater than all other wavelengths, up to the limits of the photic zone (≈1,500 m depth) and may be linked to the evolution of photosynthesis (1). BL is also potentially dangerous because it is readily absorbed by intracellular photosensitizers (e.g., porphyrin derivatives and flavins) (2). Therefore, living organisms detect and respond to BL either by photoprotection mechanisms or by maximally exploiting this environmental input, e.g., to entrain circadian rhythms and optimize photosynthetic efficiency. Given its high penetrability, BL is of utmost importance for marine species, but little is known about the BL detection mechanisms of sea plants. The AUREOCHROMES (AUREOs) described by Takahashi and colleagues (3) in a recent issue of PNAS are the first BL receptors identified in stramenopile algae and show a clear link to the photomorphogenesis of these organisms.
The existence of BL photoreceptors in plants has long been proposed, but only recently have the flavin-binding cryptochromes and phototropins (phot) been characterized at a molecular level (4). Phot are conserved in higher plants and in several lower plant species, where they mediate a variety of BL responses (e.g., phototropism, gametogenesis) (5). What is making this research field increasingly exciting is the awareness that BL photoreceptors are widespread among distant taxa and are well represented in both eukaryotes and prokaryotes (4, 6, 7). The common feature conserved among phot-related proteins is the light-sensing, flavin-binding light–oxygen–voltage (LOV) domain, a small protein unit of ≈110 aa belonging to the PerArntSim (PAS) superfamily (8). Takahashi and colleagues (3) now show the presence of LOV proteins in the photosynthetic stramenopiles Vaucheria frigida and Fucus distichus and in a diatomean species, Thalassiosira pseudonana. These …
†To whom correspondence should be addressed. E-mail: aba.losi{at}fis.unipr.it
