HOW PHYTOPLASMA TURN THEIR PLANT HOSTS INTO THEIR LIVING-DEAD SERVANTSHOW PHYTOPLASMA TURN THEIR PLANT HOSTS INTO THEIR LIVING-DEAD SERVANTS

10th Apr 2014

Scientists have uncovered how bacterial parasites can turn plants into the living dead.

“For the first time, we can reveal how this remarkable manipulation takes place,” says Saskia Hogenhout from the John Innes Centre.

“In that sense, the plant world is ahead of animal biology – where manipulations also take place but no mechanisms have been uncovered to show how.”

The plant parasite in her study, Aster Yellows phytoplasma, needs insect hosts to spread and plant hosts on which to grow. It induces the plant to transform its flowers into leaf tissue, sacrificing its reproductive success and becoming sterile. It is now a zombie plant – dead to the future and destined to benefit only the survival of the bacteria.

Working on the model plant Arabidopsis thaliana, Hogenhout and collaborators Gerco Angenent and Richard Immink at Wageningen University in the Netherlands, have discovered that phytoplasma protein SAP54 is essential to this process. It is dependent for its activity on a family of plant proteins called RAD23.

Via the SAP54 and RAD23 proteins, the plant is coerced into transforming its flowers into leaf-like material and becomes more attractive to leafhoppers for colonization. The leafhoppers pick up the bacteria from infected plants while feeding and then can spread the bacterial pathogen to yet more plants.

“This parasite is incapable of surviving without its insect and plant hosts and we showed that a parasite protein connects distinct processes in its host plant to manipulate both the plant and the insect vector,” says Professor Hogenhout.

“It is fascinating to consider that this bacterium is able to manipulate the way plants grow and the way insects behave to suit its own needs,” says JIC’s Dr Allyson MacLean, first author on the study to be published in PLOS Biology.

The study sets the stage for understanding how other plant parasites, such as fungi, reprogram plant development. In another recent study, Hogenhout collaborated with scientists at The Sainsbury Laboratory to gain the first insights into how a fungal parasite is able to create pseudoflowers mimicking buttercups. Creating these flowers in a relative of broccoli from the mustard family helps attract insects that spread the spores of the fungus.

Allyson M. MacLean, Zigmunds Orlovskis, Krissana Kowitwanich, Anna M. Zdziarska, Gerco C. Angenent, Richard G. H. Immink, Saskia A. Hogenhout. Phytoplasma Effector SAP54 Hijacks Plant Reproduction by Degrading MADS-box Proteins and Promotes Insect Colonization in a RAD23-Dependent Manner. PLoS ONE 2014;  http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001835

Adapted from this John Innes Centre Press Release.