Light Sensing by Fungi - YSUcrcooper01.people.ysu.edu/BIOL 6949-Fungal Light Sensing.pdf · BIOL...
Transcript of Light Sensing by Fungi - YSUcrcooper01.people.ysu.edu/BIOL 6949-Fungal Light Sensing.pdf · BIOL...
BIOL 6949: Cellular and Molecular Mycology
Fall 2011
Lecture: Fungal Light Sensing 1
Light Sensing by Fungi
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
Disclaimer: This lecture slide presentation is intended solely for educational purposes. Many of the images contained herein are the property of the original owner, as indicated within the figure itself or within the figure legend. These images are used only for illustrative purposes within the context of this lecture material. Use of these images outside the purpose of this presentation may violate the rights of the original owner. Dr. Cooper and Youngstown State University assume no responsibility for the unauthorized use of the material contained herein.
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
Fungi and Light
• Why benefit(s) do fungi derive from sensing light?
• A common feature is the change in spore production in response to light
• Linkage between light response and virulence • Regulation of secondary metabolite production • Effects on commercial mushroom cultivation • Use photosystems in fungi as models for other
organisms that sense light
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
Fungi and Light (cont.)
• Photosensory proteins are defined as proteins that regulate a signal transduction pathway in response to light
• Not all fungi sense light – Saccharomyces cerevisiae does not have an
established photosensor – Light does affect various processes in S.
cerevisiae that are not dependent upon signal transduction, e.g., respiration is inhibited by blue light
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
Photosensors in fungi. Fig. 1 from Idnurm et al. 2010. Fungal Genetics and Biology 47: 881-892
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
Fungi and Light (cont.)
• Gold standard to prove photosensory function – Observable light response – Measure response over a range of wavelengths
(action spectrum) – Identify a photosensor gene or protein – Impaired response due to mutation in photosensor
gene – Isolated protein must have same absorption
spectrum as action spectrum – Protein function must explain observed behavior
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
Fungi and Light (cont.)
• Types of observable light response – Light affects sporulation – Light increases pigmentation – Phototropic response – Virulence
• Light increases pathogenicity of Histoplasma capsulatum
• Mutation in wc-1 decreases virulence in Cryptococcus neoformans and Fusarium oxysporum
BIOL 6949: Cellular and Molecular Mycology
Fall 2011
Lecture: Fungal Light Sensing 2
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
Overview of photoresponses in A. nidulans. Fig. 1 from Bayram et al. 2010. Fungal Genetics and Biology 47: 900-908
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
Fungi and Light (cont.)
• What if no response is observed? Does that mean the fungus has no photosensory system? – Need to examine various “wild-type” strains, e.g.,
laboratory strain of Aspergillus nidulans most often used was a natural Ve1 mutant
– Examine transcriptome changes in response to light
– Examine proteome changes in response to light
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
Types of Photosensors
• Major classes of photosensors include – Opsins
• Membrane-bound proteins with seven transmembrane alpha-helices that bind retinal
• Role in photosensing is not clear • Distribution among fungi is sporadic
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
Photosensors in fungi. Fig. 1 from Idnurm et al. 2010. Fungal Genetics and Biology 47: 881-892
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
Types of Photosensors (cont.)
• Major classes of photosensors include (cont.) – Phytochromes
• Chromophore that senses red and far-red light • Distribution among fungi is sporadic • In A. nidulans, FphA protein is a phytochrome
that regulates asexual/sexual transition as well as secondary metabolite production in response to light
• Function in other fungi is unknown
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
Types of Photosensors (cont.)
• Major classes of photosensors include (cont.) – Cryptochromes and photolyases
• Sense blue/UV-A light • Photolyases can repair DNA damage • Cryptochromes cannot repair DNA damage, but
– Regulate growth and development – Cell signaling – Circadian rhythms
BIOL 6949: Cellular and Molecular Mycology
Fall 2011
Lecture: Fungal Light Sensing 3
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
White Collar
• White Collar 1 (WC1) encoded by many fungi – Senses blue and near UV light – Interacts with White Collar 2 (WC2)
• Roles of WC1 – Circadian clock machinery of Neurospora crassa – Sporulation – Pigmentation – Phototropism
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
White Collar (cont.)
• Some examples of wc-1 homologs and their functions among fungi (see Table 1 in Indurm et al., 2010): – Trichoderma atroviride – blr-1: conidiation – Aspergillus nidulans – lreA: asexual/sexual
reproduction; mycotoxin biosynthesis – Fusarium oxysporum – blr1: conidiation; virulence – Phycomyces blakesleeanus – madA:
phototropism; carotene biosynthesis; sporulation – Coprinopsis cinerea – dst1: cap development
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
White Collar (cont.)
• Structure of WC-1 – Three PAS domains – The N-terminal PAS = LOV (light, oxygen, voltage)
domain – functions in light sensing – GATA class zinc finger at C-terminus – functions
as a transcription factor • WC-1 is encoded by a gene (wc-1) that is
ancient and probably derived from a single origin
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
Phylogenetics of WC-1 in fungi. Fig. 3 from Idnurm et al. 2010. Fungal Genetics and Biology 47: 881-892
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
Photoreceptor proteins from N. crassa. Fig. 1 from Corrochano. 2007. Photochem. Photobiol. Sci. 7: 725-736
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
Scheme of the general architecture of the light receptors and other proteins implicated in the photoresponses of A. nidulans. Fig. 3 from Bayram et al. 2010. Fungal Genetics and Biology 47: 900-908
BIOL 6949: Cellular and Molecular Mycology
Fall 2011
Lecture: Fungal Light Sensing 4
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
White Collar (cont.)
• White Collar 2 (WC-2) is a second photosensing protein found in most species – Encoded by wc-2 in N. crassa – WC-2 homologs are required for blue-light sensing
in basidiomycetes – WC-1 and WC-2 form a complex by physically
interacting – DNA binding domain of WC-2 is required for light-
induced transcription of the WC-1/WC-2 complex
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
White Collar (cont.)
• LOV domain proteins – Some ascomycetes also possess LOV domain
proteins – In N. crassa, designated VIVID (or VVD) – Acts as a second photosensory protein – Unknown how these proteins modulate light in
signal transduction; targets are unknown
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
Quantification of conidiospores and cleistothecia formation in A. nidulans. Fig. 2 from Bayram et al. 2010. Fungal Genetics and Biology 47: 900-908
BIOL 6949 (Spring 2011) Copyright © 2011 Chester R. Cooper, Jr.
A simplified model for the photoactivation of gene expression by the WC complex. Fig. 2 from Corrochano. 2007. Photochem. Photobiol. Sci. 7: 725-736