How a pathogen turns flowers into leaves

Scientists have uncovered how a protein produced by bacteria called phytoplasmas can transform the structures within flowers, turning them into leaf-like tissues. This discovery could help prevent significant crop losses due to phytoplasma diseases, which are expected to spread as climate change expands their insect vectors. The research utilized a synchrotron technique at the European Synchrotron (ESRF) in Grenoble, France.

Phytoplasmas are bacteria transmitted to plants by insects, and their symptoms range from dwarfism to the complete reprogramming of plant development. Normally, flowers contain sepals, petals, stamens, and carpels, but in infected plants, these organs become leaves. This alteration has economic consequences, such as reduced food production in affected crops like sunflowers, sesame, and grapevines.

The phytoplasma protein PHYLOY, specifically from Candidatus Phytoplasma asteris (onion yellows strain), targets plant proteins known as MADS-box transcription factors (MTFs), which are crucial for flower development. By mimicking the structure of MTFs, PHYLOY interferes with their function, leading to the conversion of floral organs into leaves.

Understanding this interaction could lead to the development of strategies to mitigate the impact of phytoplasmas on agriculture. The study used synchrotron radiation scattering to observe how PHYLOY interacts with three MTFs, revealing that PHYLOY can bind various combinations of these factors. Researchers found that specific structural features of PHYLOY enable it to recognize multiple MTFs, allowing it to disrupt their normal function.

The researchers aim to obtain the high-resolution crystal structure of the MTF-PHYLOY complex to design inhibitors that could prevent this interaction and protect crops from the effects of phytoplasma diseases.