New Preprint! Engineering quantitative root disease resistance in barley by targeting conserved SCAR susceptibility genes without compromising seed yield or mycorrhizal symbiosis. This work has been led by @binebrumm.bsky.social www.biorxiv.org/content/10.6...
🧵1/X 🚨New Preprint🚨 Root pathogens are hard to manage, and we know little about plant genes enabling infection (susceptibility genes). Here, we show that SCARs are susceptibility factors in barley roots - and their loss affects pathogens/symbionts in distinct ways www.biorxiv.org/content/10.6...
Thank you! And I hope so, yes! There’s a long tradition for c6A research in the Biochem Department!
Any questions/comments? 🙂
(2/2): Same applies to Aron Ferenczi & Attila Molnar (@edinburgh-uni.bsky.social) as well as my (former, now graduated) PhD colleagues @jmlawrence.bsky.social & @scaralbi.bsky.social. Thanks also to all the funders (@gatescambridge.bsky.social, @ukri.org, ...)
The "Thank you" section (1/2): I'm grateful to my PhD supervisor Chris Howe (@cambiochem.bsky.social) for his perseverance and support throughout this project. Without @lauratwey.bsky.social, @laurinikkanen.bsky.social & @yagut.bsky.social (@utu.fi) this project would not have been possible!
(3/3): DISCO! 🪩💃🕺
(2/3): For the more mechanistically inclined: We propose a role for c6A in thiol-based redox regulation in the thylakoid lumen, with implications for photoprotection mechanisms such as state transitions.
Why you should care (1/3): We provide new insights into how photosynthetic organisms acclimatise to stressful light conditions, a key part of understanding plant resilience.
(4/4): These energetic imbalances of photosynthesis resulted in elevated photoinhibition, and eventually lead to cell damage (i.e. a growth phenotype).
Figure 3: c6A affects the redox state of the PQ pool, the redox kinetics of b hemes in cytochrome b6f and the quantum yield of PSII. a, Chlorophyll fluorescence induction measurements (OJIP curves) of c6A mutant strains and WT grown under photomixotrophic continuous light (30 µmolphotons m-2 s-1) conditions and normalized to F0 and FP (n = 3 biological replicates ±SD). b, Comparison of the normalized fluorescence at inflection point FJ (2.4 ms) from a. Asterisks indicate a significant difference (p < 0.05) as determined by one-way ANOVA and post-hoc pairwise two-sided t-test (n = 3 biological replicates ±SD). c, Raw steady-state fluorescence yield F’ in Volts (V) of c6A-KO and WT grown under standard conditions and exposed to a DISCO Light regime (on top of box) in a DUAL-PAM-100 spectrometer (n = 3 biological replicates ±SD). d, 1-qL values in the light phases of c6A-KO and WT grown under standard conditions and exposed to the same light protocol as in c (n = 3 biological replicates ±SD, asterisk: significant difference (p < 0.001) as determined by two-sided t-test). e, Redox changes of b hemes in c6A mutant strains and WT grown under standard conditions and exposed to DCMU (competitive inhibitor of the QB site in PSII), methyl viologen (MV, electron acceptor of PSI) or dibromothymoquinone (DBMIB, b6f QP site blocker). Samples were exposed to green light (500 µmolphotons m-2 s-1, green bar) in a JTS‑10 spectrometer (n = 3 biological replicates ±SD). f, Photosystem II quantum yield, Y(II), of c6A-KO and WT grown under standard conditions and exposed to the same light protocol as in c (n = 3 biological replicates ±SD).
(3/4): Without c6A, the light harvesting balance shifts toward PSII, leading to plastoquinone pool over-reduction. We found the signatures of an over-reduced PQ pool in PSII photosynthetic parameters, and prominently in redox kinetics of the b hemes in cytochrome b6f.
(2/4): But why and how does this growth phenotype appear? Using a whole suite of biophysical and biochemical methods, we found that c6A is involved in regulation of photosynthesis through influencing the light harvesting balance between PSI and PSII.
Figure 1: Cytochrome c6A confers a growth advantage under a fluctuating light regime. a, Schematic of the photosynthetic electron transport chain with known (black) and putative interactions (purple) of c6A marked. Proton movement (grey) and the Q-cycle (blue) are shown as arrows. b, Overlay of the crystal structures of cytochrome c6 from Chlamydomonas (orange, PDB: 1CYJ (57)) and c6A from A. thaliana (purple, PDB: 2CE0 (19)). The position of the LIP is noted with the disulfide bridge formed between the two conserved cysteine residues (yellow sticks). The amino acid residues at position 52 were found to affect the heme environment contributing to the low midpoint potential of c6A compared to c6 or plastocyanin (stick model and labelled with a green diamond) (15). c, Optical density (OD750nm) growth curve of c6A mutant strains and WT under continuous light (30 µmolphotons m-2 s-1) in either photoautotrophy or -mixotrophy and DISCO Light and photomixotrophy (n = 3 biological replicates ±SD). Statistical testing was carried out with repeated measures ANOVA. Post hoc pairwise two-sided t-tests at each time point were performed if the interaction effect of time and strain on OD750nm in the ANOVA was significant (ptime:strain < 0.05) comparing WT (pink) or c6A-OE (green) against c6A-KO (p < 0.05: *, p ≤ 0.1: #). d, DISCO Light (Darkness Interrupted by Short COnstant Light) consists of alternating 2 min darkness followed by 2 min of high light pulses (12 s high light (700 µmolphotons m-2 s-1) & 12 s darkness). e, Visual differences of the c6A mutant and WT cultures of at day 3 of growth in DISCO Light.
The results (1/4): Enter DISCO Light, a harsh, rapidly fluctuating light condition, like turbulent water movements or wind blowing through a forest canopy. When we grew a c6A knock-out mutant of Chlamydomonas under these dynamic conditions, we saw a growth penalty!
(2/2): First, c6A was believed to be able to replace plastocyanin, just like c6. But in 2003, that hypothesis was overturned, as c6A couldn't transfer electrons to PSI. Despite c6A's high degree of conservation (similar to plastocyanin) its function remained a mystery.
The backstory (1/2): In 2002, Cytochrome c6A was discovered, challenging the view that plants had lost the family of cytochrome c6 and homologues. c6 can be used for photosynthetic electron transport in cyanobacteria, red algae, and some green algae (doi.org/10.1093/gbe/...).
Algae in the DISCO! (AI generated image before it was cringy to do that)
🚨 New Preprint! 🚨
For my PhD, I investigated an over 20-year-old mystery in photosynthesis: What does the highly conserved but enigmatic protein cytochrome c6A actually do?
We found: c6A helps algae stayin' alive in the "DISCO". 🪩
See the thread below & read the preprint: doi.org/10.64898/202...
Any questions/comments? 🙂
(2/2): Same applies to Aron Ferenczi & Attila Molnar (@edinburgh-uni.bsky.social) as well as my (former, now graduated) PhD colleagues @jmlawrence.bsky.social & @scaralbi.bsky.social. Thanks also to all the funders (@gatescambridge.bsky.social, @ukri.org, ...)
The "Thank you" section (1/2): I'm grateful to my PhD supervisor Chris Howe (@cambiochem.bsky.social) for his perseverance and support throughout this project. Without @lauratwey.bsky.social, @laurinikkanen.bsky.social & @yagut.bsky.social (@utu.fi) this project would not have been possible!
(3/3): DISCO! 🪩💃🕺
(2/3): For the more mechanistically inclined: We propose a role for c6A in thiol-based redox regulation in the thylakoid lumen, with implications for photoprotection mechanisms such as state transitions.
Why you should care (1/3): We provide new insights into how photosynthetic organisms acclimatise to stressful light conditions, a key part of understanding plant resilience.
(4/4): These energetic imbalances of photosynthesis resulted in elevated photoinhibition, and eventually lead to cell damage (i.e. a growth phenotype).
Figure 3: c6A affects the redox state of the PQ pool, the redox kinetics of b hemes in cytochrome b6f and the quantum yield of PSII. a, Chlorophyll fluorescence induction measurements (OJIP curves) of c6A mutant strains and WT grown under photomixotrophic continuous light (30 µmolphotons m-2 s-1) conditions and normalized to F0 and FP (n = 3 biological replicates ±SD). b, Comparison of the normalized fluorescence at inflection point FJ (2.4 ms) from a. Asterisks indicate a significant difference (p < 0.05) as determined by one-way ANOVA and post-hoc pairwise two-sided t-test (n = 3 biological replicates ±SD). c, Raw steady-state fluorescence yield F’ in Volts (V) of c6A-KO and WT grown under standard conditions and exposed to a DISCO Light regime (on top of box) in a DUAL-PAM-100 spectrometer (n = 3 biological replicates ±SD). d, 1-qL values in the light phases of c6A-KO and WT grown under standard conditions and exposed to the same light protocol as in c (n = 3 biological replicates ±SD, asterisk: significant difference (p < 0.001) as determined by two-sided t-test). e, Redox changes of b hemes in c6A mutant strains and WT grown under standard conditions and exposed to DCMU (competitive inhibitor of the QB site in PSII), methyl viologen (MV, electron acceptor of PSI) or dibromothymoquinone (DBMIB, b6f QP site blocker). Samples were exposed to green light (500 µmolphotons m-2 s-1, green bar) in a JTS-10 spectrometer (n = 3 biological replicates ±SD). f, Photosystem II quantum yield, Y(II), of c6A-KO and WT grown under standard conditions and exposed to the same light protocol as in c (n = 3 biological replicates ±SD).
(3/4): Without c6A, the light harvesting balance shifts toward PSII, leading to plastoquinone pool over-reduction. We found the signatures of an over-reduced PQ pool in PSII photosynthetic parameters, and prominently in redox kinetics of the b hemes in cytochrome b6f.
(2/4): But why and how does this growth phenotype appear? Using a whole suite of biophysical and biochemical methods, we found that c6A is involved in regulation of photosynthesis through influencing the light harvesting balance between PSI and PSII.
Figure 1: Cytochrome c6A confers a growth advantage under a fluctuating light regime. a, Schematic of the photosynthetic electron transport chain with known (black) and putative interactions (purple) of c6A marked. Proton movement (grey) and the Q-cycle (blue) are shown as arrows. b, Overlay of the crystal structures of cytochrome c6 from Chlamydomonas (orange, PDB: 1CYJ (57)) and c6A from A. thaliana (purple, PDB: 2CE0 (19)). The position of the LIP is noted with the disulfide bridge formed between the two conserved cysteine residues (yellow sticks). The amino acid residues at position 52 were found to affect the heme environment contributing to the low midpoint potential of c6A compared to c6 or plastocyanin (stick model and labelled with a green diamond) (15). c, Optical density (OD750nm) growth curve of c6A mutant strains and WT under continuous light (30 µmolphotons m-2 s-1) in either photoautotrophy or -mixotrophy and DISCO Light and photomixotrophy (n = 3 biological replicates ±SD). Statistical testing was carried out with repeated measures ANOVA. Post hoc pairwise two-sided t-tests at each time point were performed if the interaction effect of time and strain on OD750nm in the ANOVA was significant (ptime:strain < 0.05) comparing WT (pink) or c6A-OE (green) against c6A-KO (p < 0.05: *, p ≤ 0.1: #). d, DISCO Light (Darkness Interrupted by Short COnstant Light) consists of alternating 2 min darkness followed by 2 min of high light pulses (12 s high light (700 µmolphotons m-2 s-1) & 12 s darkness). e, Visual differences of the c6A mutant and WT cultures of at day 3 of growth in DISCO Light.
The results (1/4): Enter DISCO Light, a harsh, rapidly fluctuating light condition, like turbulent water movements or wind blowing through a forest canopy. When we grew a c6A knock-out mutant of Chlamydomonas under these dynamic conditions, we saw a growth penalty!
(2/2): First, c6A was believed to be able to replace plastocyanin, just like c6. But in 2003, that hypothesis was overturned, as c6A couldn't transfer electrons to PSI. Despite c6A's high degree of conservation (similar to plastocyanin) its function remained a mystery.
The backstory (1/2): In 2002, Cytochrome c6A was discovered, challenging the view that plants had lost the family of cytochrome c6 and homologues. c6 can be used for photosynthetic electron transport in cyanobacteria, red algae, and some green algae (doi.org/10.1093/gbe/...).
We are very close to reaching the registration cap for MECS2026. Given the strong interest, we have increased the number of participants from 100 to 120 and extended registration until April 12. Please note, however, that we can no longer accept poster submissions.
Trichomes on an Arabidopsis thaliana leaf (here shown using electron microscopy) are formed by a single cell adopting this spiked shape (top images). Arabidopsis plants without a SCAR/WAVE gene cannot form properly shaped trichomes, because their inner cytoskeleton control is impaired (bottom images). Images by Sabine Brumm.
@binebrumm.bsky.social, together with @dromius.bsky.social team colleagues, unveiled how key proteins act as 'sculptors' in plant cells, taking on different roles to shape development
Read more www.slcu.cam.ac.uk/news/plant-c...
And full paper doi.org/10.1126/scia...