Bacterial Protein Makes “Zombie” Plant
September 18, 2021
- Obligate parasite is an organism that completes its life-cycle by exploiting a suitable host.
- Some obligate parasites induce significant observable changes in their hosts which allows the parasites to be transmitted easily to other trophic levels.
- However, the mechanisms underlying these changes are not well understood.
- Researchers demonstrated how SAP05 protein effectors from pathogenic phytoplasmas transmitted by insect take control of numerous developmental processes in plants.
- Protein effectors are small molecules that selectively bind to a protein and modulate its biological activity.
- Phytoplasma is an obligate intracellular parasite of plant phloem tissue.
- Phytoplasma lacks cell wall and mainly transmitted by leafhoppers but also by plant propagation materials and seeds.
- These protein effectors make the host lifespan longer and promote witches’ broom-like growth of leaf and sterile shoots, parts colonized by phytoplasmas and vectors.
- Normally, proteins not needed by plants are tagged with ubiquitin marking them as to be degraded.
- A machinery called proteasome then degrades the tagged proteins for recycling.
- SAP05 hijacks the protein degradation process and causes plant proteins involved in regulating growth to be degraded.
- SAP05 binds to both regulatory protein and the proteasome facilitating the degradation of these protein.
- Without these regulatory proteins, plant growth is affected which results in multiple vegetative shoot and tissue growth and suspension of plant aging.
- Ubiquitin receptor is common among eukaryotic organisms; however, SAP05 does not bind to insect ubiquitin receptor.
- Researchers pinpointed two amino acids in proteasome that are required to interact with SAP05.
- If these two amino acids in plant protein are replaced with amino acids from insect protein instead, they no longer interact with SAP05 and prevents the witches’ broom abnormal growth.
- The study highlights an effector protein that enables obligate parasitic phytoplasmas to promote an excess of growth development in their hosts.
- The new findings offer the possibility of manipulating two amino acids in crops to provide long-lasting resilience against phytoplasmas and the effect of SAP05.