How a pathogen turns flowers into leaves
European Synchrotron Radiation Facility
image:
Normal Arabidopsis flower versus Arabidopsis flower when phyllogen is present
credit: @Zubieta
view moreCredit: Chloe Zubieta
Scientists have found how a protein produced by bacteria disrupts the mechanism that controls flower development in plants, turning reproductive organs into leaf-like structures. These findings shed light on a plant disease that is expected to spread as climate change expands the range of its insect vectors in northern latitudes. They used synchrotron technique at the ESRF, the European Synchrotron in Grenoble, France. The results are the Editor’s Pick in the Journal of Biological Chemistry.
Phytoplasmas are bacteria that are transmitted to plants by insects. The symptoms of the pathogen can range from triggering dwarfism in the plant to essentially reprogramming plant development: instead of flowers, all the floral organs- sepals, petals, stamen and carpels- are converted to leaves, with diverse crops such as sunflowers, sesame and grapevine affected.
This effect can have economic consequences, as food might not be as easily available in damaged crops. For example, outbreaks of phytoplasma coconut lethal yellowing disease in Africa since the 1930s has led to devastating crop losses up to 40% in Tanzania and 20% in Ghana. In addition, climate change has increased the presence of insects in more northern latitudes, which increases the presence of phytoplasmas. “Understanding how the insects hijack the plant’s own developmental machinery could help us find strategies to hopefully mitigate their impact on agriculture”, explains Chloe Zubieta, CEA researcher at Laboratoire de Physiologie Cellulaire et Végétale, ESRF visiting scientist and leader of the study.
Zubieta joined forces with ESRF scientists Mark Tully and Max Nanao to study a phytoplasma protein called PHYLOY (phyllogen protein from Candidatus Phytoplasma asteris, onion yellows strain), which interferes with the plant’s normal development. It does this by targeting plant proteins called MADS-box transcription factors (MTFs).
MTFs play an important role in deciding how a flower develops. They work together in groups of four, binding to DNA and switching on the genes that tell the plant which parts of the flower to produce.
The researchers used a synchrotron technique called Small X-ray scattering (SAXS) on ESRF’s beamline BM29 to study how PHYLOY interacts with three important MTFs. Their experiments showed that PHYLOY can interact with a wider range of MTF combinations than previously thought. “We can observe flexibility in the data and we think this corresponds to the interaction plasticity of phyllogen and host plant transcription factors,” notes Mark Tully, ESRF scientist at BM29.
The researchers then changed individual parts of these proteins using a technique called site directed mutagenesis and found that they could either prevent or enable the interactions. This showed that PHYLOY recognises specific features shared by different MTFs, allowing the pathogen to interfere with the plant’s developmental machinery by structural mimicry.
By preventing MTF proteins from working together properly, the phytoplasma protein changes the identity of floral organs, causing them to develop into leaf-like structures.
“We are working on obtaining the high-resolution crystal structure of the MTF-PHYLOY complex and hope to use these data, in combination with high throughput virtual screening, to design inhibitors of this interaction,” comments Max Nanao, ESRF scientist.
The scientists used the ESRF to study a phytoplasma protein called PHYLOY, which interferes with the plant’s normal development.
Credit
Journal of Biological Chemistry
The scientists used the ESRF to demonstrate how a pathogen turns flowers into leaves - Here Chloe Zubieta, CEA, during the experiment at the ESRF's beamline BM29.
Credit
ESRF
Journal
Journal of Biological Chemistry
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
The phytoplasma effector, phyllogen, structurally mimics host plant MADS transcription factors
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