Convergence and divergence of the photoregulation of pigmentation and cellular morphology inFremyella diplosiphon

Abstract

Photosynthetic pigment accumulation and cellular and filament morphology are regulated reversibly by green light (GL) and red light (RL) in the cyanobacterium Fremyella diplosiphon during complementary chromatic adaptation (CCA). The photoreceptor RcaE (regulator of chromatic adaptation), which appears to function as a light-responsive sensor kinase, controls both of these responses. Recent findings indicate that downstream of RcaE, the signaling pathways leading to light-dependent changes in morphology or pigment synthesis and/or accumulation, branch and utilize distinct molecular components. We recently reported that the regulation of the accumulation of the GL-absorbing photosynthetic accessory protein phycoerythrin (PE) and photoregulation of cellular morphology are largely independent, as many mutants with severe PE accumulation defects do not have major disruptions in the regulation of cellular morphology. Furthermore, morphology can be disrupted under GL without impacting GL-dependent PE accumulation. Most recently, however, we determined that the disruption of the cpeR gene, which encodes a protein that is known to function as an activator of PE synthesis under GL, results in disruption of cellular morphology under GL and RL. Thus, apart from RcaE, CpeR is only the second known regulator to impact morphology under both light conditions in F. diplosiphon.

Analysis of the light intensity dependence of the growth ofSynechocystisand of the light distribution in a photobioreactor energized by 635 nm light

“…Even though the bacterial life cycle is usually the major determinant of morphological traits, including cell size, several studies reported that cyanobacteria modify their morphology to optimize their functionality to exogenous factors in natural contexts ( Montgomery, 2015 ). However, the mechanisms by which light conditions, including light intensity, influence cell morphology, including cell size, are understudied ( Pattanaik, Whitaker & Montgomery, 2011 ). Table 1 shows Synechocystis cell size changes in response to increasing light intensities.…”

Peer Review #1 of "Analysis of the light intensity dependence of the growth of Synechocystis and of the light distribution in a photobioreactor energized by 635 nm light (v0.1)"

“…Even though the bacterial life cycle is usually the major determinant of morphological traits, including cell size, several studies reported that cyanobacteria modify their morphology to optimize their functionality to exogenous factors in natural contexts (Montgomery, 2015). However, the mechanisms by which light conditions, including light intensity, influence cell morphology, including cell size, are understudied (Pattanaik, Whitaker & Montgomery, 2011). We then examined the effect of long-term acclimation to increasing intensities of orange-red light by estimating the Chl a content in Synechocystis through the measurement of the OD 680 /OD 720 ratio (Table S2).…”

Fortuitous events in the evolution of Light-dependent Protochlorophyllide Oxidoreductase

“…The action spectra of LPOR reveals that it is ineffective in green light, in such cases LIPOR compensates for the low LPOR activity. The members of the (Microchaetaceae) Fremyella diplosiphon (Shui et al, 2009;Pattanaik et al, 2011), (Nostocaceae) N. punctiforme (Hirose et al, 2013), (Rivularariaceae) Gloeotrichia 583 (Stowe et al, 2011) depict an interesting phenotype as an example of the complementary chromatic adaptation by alternating their photosynthetic pigments and enzymes under fluctuating light conditions (Hirose et al, 2013). It would not be hyperbolic to say that they can sense a rainbow of colors ranging from red, blue, green and violet (Grossman, 2003;Bordowitz and Montgomery, 2008;Kehoe, 2010).…”