scholarly journals Tips and turns of bacteriophytochrome photoactivation

2020 ◽  
Vol 19 (11) ◽  
pp. 1488-1510
Author(s):  
Heikki Takala ◽  
Petra Edlund ◽  
Janne A. Ihalainen ◽  
Sebastian Westenhoff
Keyword(s):  
Red Light ◽  
Current Understanding ◽  
Special Focus ◽  
Light Sensing

Phytochromes are red light-sensing photoreceptors. Here we review the current understanding of phytochrome photoactivation, with a special focus on bacteriophytochromes and their crystallographic studies.

scholarly journals Red- and Blue-Light Sensing in the Plant Pathogen Alternaria alternata Depends on Phytochrome and the White-Collar Protein LreA

mBio ◽  
2019 ◽  
Vol 10 (2) ◽  
Author(s):  
Olumuyiwa Igbalajobi ◽  
Zhenzhong Yu ◽  
Reinhard Fischer
Keyword(s):  
Blue Light ◽  
Alternaria Alternata ◽  
Red Light ◽  
White Collar ◽  
Nuclear Accumulation ◽  
Model Organisms ◽  
Light Induction ◽  
Content Type ◽  
High Osmolarity ◽  
Light Sensing

ABSTRACT The filamentous fungus Alternaria alternata is a common postharvest contaminant of food and feed, and some strains are plant pathogens. Many processes in A. alternata are triggered by light. Interestingly, blue light inhibits sporulation, and red light reverses the effect, suggesting interactions between light-sensing systems. The genome encodes a phytochrome (FphA), a white collar 1 (WC-1) orthologue (LreA), an opsin (NopA), and a cryptochrome (CryA) as putative photoreceptors. Here, we investigated the role of FphA and LreA and the interplay with the high-osmolarity glycerol (HOG) mitogen-activated protein (MAP) kinase pathway. We created loss-of function mutations for fphA, lreA, and hogA using CRISPR-Cas9 technology. Sporulation was reduced in all three mutant strains already in the dark, suggesting functions of the photoreceptors FphA and LreA independent of light perception. Germination of conidia was delayed in red, blue, green, and far-red light. We found that light induction of ccgA (clock-controlled gene in Neurospora crassa and light-induced gene in Aspergillus nidulans) and the catalase gene catA depended on FphA, LreA, and HogA. Light induction of ferA (a putative ferrochelatase gene) and bliC (bli-3, light regulated, unknown function) required LreA and HogA but not FphA. Blue- and green-light stimulation of alternariol formation depended on LreA. A lack of FphA or LreA led to enhanced resistance toward oxidative stress due to the upregulation of catalases and superoxide dismutases. Light activation of FphA resulted in increased phosphorylation and nuclear accumulation of HogA. Our results show that germination, sporulation, and secondary metabolism are light regulated in A. alternata with distinct and overlapping roles of blue- and red-light photosensors. IMPORTANCE Light controls many processes in filamentous fungi. The study of light regulation in a number of model organisms revealed an unexpected complexity. Although the molecular components for light sensing appear to be widely conserved in fungal genomes, the regulatory circuits and the sensitivity of certain species toward specific wavelengths seem different. In N. crassa, most light responses are triggered by blue light, whereas in A. nidulans, red light plays a dominant role. In Alternaria alternata, both blue and red light appear to be important. In A. alternata, photoreceptors control morphogenetic pathways, the homeostasis of reactive oxygen species, and the production of secondary metabolites. On the other hand, high-osmolarity sensing required FphA and LreA, indicating a sophisticated cross talk between light and stress signaling.

scholarly journals Phytochrome A Function in Red Light Sensing

2007 ◽  
Vol 2 (5) ◽  
pp. 383-385 ◽  
Author(s):  
Keara A. Franklin ◽  
Garry C. Whitelam
Keyword(s):  
Red Light ◽  
Phytochrome A ◽  
Light Sensing

scholarly journals Differential responses of coral larvae to the colour of ambient light guide them to suitable settlement microhabitat

2015 ◽  
Vol 2 (10) ◽  
pp. 150358 ◽  
Author(s):  
Marie E. Strader ◽  
Sarah W. Davies ◽  
Mikhail V. Matz
Keyword(s):  
Fluorescent Protein ◽  
Critical Role ◽  
Red Light ◽  
Green Light ◽  
Ambient Light ◽  
Coral Larvae ◽  
Acropora Millepora ◽  
Light Sensing ◽  
Natal Habitat

Reef-building corals produce planktonic planula larvae that must select an appropriate habitat to settle and spend the rest of their life, a behaviour that plays a critical role in survival. Here, we report that larvae obtained from a deep-water population of Pseudodiploria strigosa settled more readily under blue light and in the dark, which aligns well with the light field characteristics of their natal habitat. By contrast, larvae of the shallow-water coral Acropora millepora settled in high proportions under blue and green light while settlement was less in the dark. Acropora millepora larvae also showed reduced settlement under red light, which should be abundant at shallow depth. Hypothesizing that this might be a mechanism preventing the larvae from settling on the exposed upwards-facing surfaces, we quantified A. millepora settlement in manipulated light chambers in situ on the reef. While A. millepora larvae naturally preferred settling on vertical rather than exposed horizontal surfaces, swapping the colours of upwards-facing and sideways-facing light fields was sufficient to invert this preference. We also tested if the variation in intrinsic red fluorescence in A. millepora larvae correlates with settlement rates, as has been suggested previously. We observed this correlation only in the absence of light, indicating that larval red fluorescent protein is probably not directly involved in light sensing. Our study reveals previously under-appreciated light-sensory capabilities in coral larvae, which could be an important axis of ecological differentiation between coral species and/or populations.

scholarly journals Seeing the Light: The Roles of Red- and Blue-Light Sensing in Plant Microbes

2018 ◽  
Vol 56 (1) ◽  
pp. 41-66 ◽  
Author(s):  
Gwyn A. Beattie ◽  
Bridget M. Hatfield ◽  
Haili Dong ◽  
Regina S. McGrane
Keyword(s):  
Blue Light ◽  
Molecular Mechanisms ◽  
Red Light ◽  
Light Availability ◽  
Photosynthetic Apparatus ◽  
Light Regulation ◽  
Environmental Signals ◽  
Light Sensing ◽  
Fungal Phytopathogens ◽  
Bacteria And Fungi

Plants collect, concentrate, and conduct light throughout their tissues, thus enhancing light availability to their resident microbes. This review explores the role of photosensing in the biology of plant-associated bacteria and fungi, including the molecular mechanisms of red-light sensing by phytochromes and blue-light sensing by LOV (light-oxygen-voltage) domain proteins in these microbes. Bacteriophytochromes function as major drivers of the bacterial transcriptome and mediate light-regulated suppression of virulence, motility, and conjugation in some phytopathogens and light-regulated induction of the photosynthetic apparatus in a stem-nodulating symbiont. Bacterial LOV proteins also influence light-mediated changes in both symbiotic and pathogenic phenotypes. Although red-light sensing by fungal phytopathogens is poorly understood, fungal LOV proteins contribute to blue-light regulation of traits, including asexual development and virulence. Collectively, these studies highlight that plant microbes have evolved to exploit light cues and that light sensing is often coupled with sensing other environmental signals.

scholarly journals A deletion in the PHYD gene of the Arabidopsis Wassilewskija ecotype defines a role for phytochrome D in red/far-red light sensing.

1997 ◽  
Vol 9 (8) ◽  
pp. 1317-1326 ◽  
Author(s):  
M J Aukerman ◽  
M Hirschfeld ◽  
L Wester ◽  
M Weaver ◽  
T Clack ◽  
...  
Keyword(s):  
Red Light ◽  
Light Sensing

scholarly journals The PIF1-MIR408-Plantacyanin Repression Cascade Regulates Light Dependent Seed Germination

2020 ◽  
Author(s):  
Anlong Jiang ◽  
Zhonglong Guo ◽  
Jiawei Pan ◽  
Yan Zhuang ◽  
Daqing Zuo ◽  
...  
Keyword(s):  
Seed Germination ◽  
Red Light ◽  
Experimental System ◽  
Seed Plants ◽  
Cellular Mechanisms ◽  
Light Sensing ◽  
Early Germination ◽  
Light Signals ◽  
Necessary And Sufficient ◽  
Storage Vacuole

ABSTRACTLight-sensing seed germination is a vital process for the seed plants. A decisive event in light-induced germination is degradation of the central repressor PHYTOCHROME INTERACTING FACTOR1 (PIF1). It is also known that the balance between gibberellic acid (GA) and abscisic acid (ABA) critically controls germination. But the cellular mechanisms linking PIF1 turnover to hormonal rebalancing remain elusive. Here, employing far-red light-induced Arabidopsis seed germination as the experimental system, we identified Plantacyanin (PLC) as an inhibitor of germination, which is a storage vacuole-associated blue copper protein highly expressed in mature seed and rapidly silenced during germination. Molecular analyses showed that PIF1 directly binds to the MIR408 promoter and represses miR408 accumulation, which in turn post-transcriptionally modulates PLC abundance, thus forming the PIF1-MIR408-PLC repression cascade for translating PIF1 turnover to PLC turnover during early germination. Genetic analysis, RNA-sequencing, and hormone quantification revealed that PLC is necessary and sufficient to maintain the PIF1-mediated seed transcriptome and the low-GA-high-ABA state. Furthermore, we found that PLC domain organization and regulation by miR408 are conserved features in seed plants. These results unraveled a cellular mechanism whereby PIF1-relayed external light signals are converted through PLC-based copper mobilization into internal hormonal profiles for controlling seed germination.

scholarly journals Green light perception paved the way for the diversification of GAF domain photoreceptors

2021 ◽  
Author(s):  
Nibedita Priyadarshini ◽  
Niklas Steube ◽  
Dennis Wiens ◽  
Rei Narikawa ◽  
Annegret Wilde ◽  
...  
Keyword(s):  
Red Light ◽  
Visible Region ◽  
Green Light ◽  
Ancestral Sequence ◽  
Light Harvesting Complexes ◽  
Ph Titration ◽  
Light Sensing ◽  
Ancestral Sequence Reconstruction ◽  
Sequence Reconstruction ◽  
Light Signals

AbstractPhotoreceptors are proteins that sense incident light and then trigger downstream signaling events. Phytochromes are linear tetrapyrrole-binding photoreceptors present in plants, algae, fungi, and various bacteria. Most phytochromes respond to red and far-red light signals. Among the phytochrome superfamily, cyanobacteria-specific cyanobacteriochromes show much more diverse optical properties covering the entire visible region. Both phytochromes and cyanobacteriochromes share the GAF domain scaffold to cradle the chromophore as the light-sensing region. It is unknown what physiological demands drove the evolution of cyanobacteriochromes in cyanobacteria. Here we utilize ancestral sequence reconstruction and report that the resurrected ancestral cyanobacteriochrome proteins reversibly respond to green and red light signals. pH titration analyses indicate that the deprotonation of the bound phycocyanobilin chromophore enables the photoreceptor to perceive green light. The ancestral cyanobacteriochromes show modest thermal reversion to the green light-absorbing form, suggesting that they evolved to sense green-rich irradiance rather than red light, which is preferentially utilized for photosynthesis. In contrast to plants and green algae, many cyanobacteria can utilize green light for photosynthesis with their special light-harvesting complexes, phycobilisomes. The evolution of green/red sensing cyanobacteriochromes may therefore have allowed ancient cyanobacteria to acclimate to different light environments by rearranging the absorption capacity of the cyanobacterial antenna complex by chromatic acclimation.Significance StatementLight serves as a crucial environmental stimulus affecting the physiology of organisms across all kingdoms of life. Photoreceptors serve as important players of light responses, absorbing light and actuating biological processes. Among a plethora of photoreceptors, cyanobacteriochromes arguably have the wealthiest palette of color sensing, largely contributing to the success of cyanobacteria in various illuminated habitats. Our ancestral sequence reconstruction and the analysis of the resurrected ancestral proteins suggest that the very first cyanobacteriochrome most probably responded to the incident green-to-red light ratio, in contrast to modern red/far-red absorbing plant phytochromes. The deprotonation of the light-absorbing pigment for green light-sensing was a crucial molecular event for the invention of the new class of photoreceptors with their huge color tuning capacity.

scholarly journals Stigmatization in dermatology with a special focus on psoriatic patients

2017 ◽  
Vol 71 (0) ◽  
pp. 0-0 ◽  
Author(s):  
Dimitre Dimitrov ◽  
Jacek C. Szepietowski
Keyword(s):  
Social Norms ◽  
Skin Disease ◽  
Skin Diseases ◽  
Selection Process ◽  
Skin Lesions ◽  
Cultural Factors ◽  
Current Understanding ◽  
Special Focus ◽  
Skin Conditions ◽  
Key Phrases

A stigma is currently defined as a discrediting mark, biological or social, that sets a person off from others and disrupts interactions with them. People who differ from social norms in some respect are often negatively labeled. A number of medical conditions are recognized at present as stigmatizing their sufferers and certain skin diseases are among them. The article aimed to analyze the current understanding about stigmatization among dermatological patients, especially those with psoriasis. We performed our search on PubMed up to November 2016 and utilized combinations of key phrases containing such words as stigmatization, skin, dermatology, names of various skin conditions (psoriasis, vitiligo, acne, etc.). Following a precise selection process, 58 articles remained. Stigmatization seems to be a common and important problem in dermatology. Psoriasis appears as the most frequently studied skin disease (37.2% of articles). It was followed by vitiligo (13.7%) and leprosy (8.6%). Mainly, the visibility of skin lesions as well as cultural factors contribute to the feeling of stigmatization. There is a need for more research in the field of stigmatization in dermatological conditions and an urgent need for the creation of special anti-stigmatization program/programs for patients suffering from dermatoses.

A Deletion in the PHYD Gene of the Arabidopsis Wassilewskija Ecotype Defines a Role for Phytochrome D in Red/Far-Red Light Sensing

1997 ◽  
Vol 9 (8) ◽  
pp. 1317 ◽  
Author(s):  
Milo J. Aukerman ◽  
Matthew Hirschfeld ◽  
Lynn Wester ◽  
Michael Weaver ◽  
Ted Clack ◽  
...  
Keyword(s):  
Red Light ◽  
Light Sensing
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