A chimeric photoreceptor gene, NEOCHROME, has arisen twice during plant evolution

Abstract

Although most plant species from algae to flowering plants use blue light for inducing phototropism and chloroplast movement, many ferns, some mosses, and green algae use red as well as blue light for the regulation of these responses, resulting in better sensitivity at low light levels. During their evolution, ferns have created a chimeric photoreceptor (phy3 in Adiantum) between phytochrome (phy) and phototropin (phot) enabling them to use red light effectively. We have identified two genes resembling Adiantum PHY3, NEOCHROME1 and NEOCHROME2 (MsNEO1 and MsNEO2), in the green alga Mougeotia scalaris, a plant famous for its light-regulated chloroplast movement. Like Adiantum PHY3, both MsNEO gene products show phytochrome-typical bilin binding and red͞far-red reversibility, the difference spectra matching the known action spectra of light-induced chloroplast movement in Mougeotia. Furthermore, both genes rescue red-light-induced chloroplast movement in Adiantum phy3 mutants, indicating functional equivalence. However, the fern and algal genes seem to have arisen independently in evolution, thus providing an intriguing example of convergent evolution. convergent evolution ͉ Mougeotia

A phytochrome–phototropin light signaling complex at the plasma membrane

“…The data presented here seem to resolve this problem in the case of mosses. On the other hand, in certain algal and fern groups, neochrome photoreceptors have evolved to fulfill this function (14,15,36). Neochromes comprise an N-terminal phytochrome sensory module attached to an almost complete phototropin moiety.…”

“…In general, however, phytochromes are not considered to be membrane-associated, Pr at least being freely cytosolic. This paradox was partly solved in cases involving ferns (14) and algae (15) with the discovery that the photoreceptor responsible comprised a phytochrome sensory module fused to a phototropin blue light (B) receptor. This chimeric molecule was named neochrome.…”

The Structure of Phytochrome: A Picture Is Worth a Thousand Spectra

“…Signaling by plant phytochromes also involves protein-protein interactions with the N-terminal part of the protein (Ni et al, 1999;Oka et al, 2004), although it is not yet known whether these interactions are actually mediated via the conserved photosensory core (P2-P3-P4), via the N-terminal Ser/Thr-rich extension specific to plant phytochromes, or both. In more primitive plants and algae, atypical phytochromes have been described in which the C-terminal region has been replaced by fortuitous gene fusions with phototropins and other eukaryotic Ser/Thr kinases (Thü mmler et al, 1992;Nozue et al, 1998;Suetsugu et al, 2005). Bacteriophytochromes that lack recognizable kinase output domains have also been reported (Giraud et al, 2002;Karniol et al, 2005).…”

Phytochrome-mediated light signaling in plants: emerging trends

“…Mougeotia, a unique chimeric photoreceptor, neochrome, has been identified, which can perceive light both in the red/far-red as well as UV-A/blue region to regulate chloroplast relocation and other plant responses (Suetsugu et al, 2005;Sato et al, 2007;Suetsugu and Wada, 2007). There are also reports substantiating many green-light (GL)-mediated responses in plants and, consequently, there are speculations for the occurrence of even a zeaxanthin-based compound as a green light receptor (Frechilla et al, 2000;Talbott et al, 2003;Folta, 2004;Dhingra et al, 2006;Folta and Maruhnich, 2007).…”