Isolation and characterization of two phototropins in the freshwater green alga, Spirogyra varians (Streptophyta, Zygnematales)

Abstract

Freshwater algae living in shallow waters have evolved various photomovement to stay in the optimum light condition for survival. Previous action-spectra investigations showed that Spirogyra filaments have phototropic movement in blue light. To decipher the genetic control of phototropic movement, two phototropin homologues were isolated from Spirogyra varians, and named SvphotA and SvphotB. Both phototropins have similar molecular structure consisted of two light-oxygen-voltage domains (LOV1, LOV2) and a serine / threonine kinase domain. SvphotA and SvphotB had 48.7% sequence identity. Phylogenetic analysis showed SvphotA and SvphotB belong to different clades suggesting early divergence, possibly before the divergence of land plants from the Zygnematales. Quantitative PCR and northern blot analysis showed that SvphotA and SvphotB responded differently to red and blue light. SvphotA was consistently expressed in the dark and in blue light, while SvphotB was expressed only when the plants were exposed to light. When the filaments were exposed to red light, SvphotA was significantly downregulated whereas SvphotB was highly upregulated. These results suggest that the two phototropins may have different roles in the photoresponse in S. varians.

Review on the biotechnological and nanotechnological potential of the streptophyte genusKlebsormidiumwith pilot data on its phycoprospecting and polyphasic identification in Bulgaria

“…Current investigations revealed that Klebsormidium contains phototropins [54] and its genome has acquired genes (some of them similar to land plants) which allow specific adaptation to terrestrial life by providing protection against the detrimental effects of high-intensity light [55]. These results are in accordance with the suggested gradual colonization of land habitats by descendents of streptophyte algae, for which the major advantage was the physiological preadaptation to terrestrial existence by their primary freshwater life style [56].…”

Red And far‐red regulation of filament movement correlates with the expression of phytochrome and FHY1 genes in Spirogyra varians (Zygnematales, Streptophyta)1

“…). We could not find any neochrome homologues in the S. varians transcriptome (Lee and Kim ). At the moment, little is known of the regulation pathway and machineries of red/far‐red light movement in freshwater algae even in the Mougeotia model (Banaś et al.…”

“…A neochrome gene which contains both phytochrome and phototropin domains has been found in M. scalaris, but the involvement of this chimeric photoreceptor in the chloroplast movement has not been demonstrated (Suetsugu et al 2005). We could not find any neochrome homologues in the S. varians transcriptome (Lee and Kim 2017a). At the moment, little is known of the regulation pathway and machineries of red/far-red light movement in freshwater algae even in the Mougeotia model (Bana s et al 2012).…”

“…The filamentous green alga Spirogyra offers a unique example of photomovement occurring at a whole‐body scale and that is controlled by the coordination of two different photoreceptors (Lee and Kim ,b). Spirogyra filaments continuously move in light, but the movement is different in blue, red, and far‐red light (Tanaka et al.…”

“…Identification of photoreceptors is essential to understand the regulation of this complicated movement. Two phototropins were characterized in Spirogyra varians , and differential expression of the phototropins in red and blue light was observed (Lee and Kim ). So far, no red‐light responsive photoreceptor has yet been characterized in Spirogyra .…”