Zombie Research at UCD

Dr. Rainer Melzer's paper, 'Convergent protein evolution enabled phytoplasmas to generate 'zombies?' was recently publisehd by 'Trends in Plant Science'. The paper examines bacterial pathogens that induce 'zombie plants' or plants that are sterile and propagate the bacteria. Dr. Melzer discusses his research below:

'Halloween is looming, and there will certainly be the one or the other zombie on the streets out there. However, whereas most (probably all) Halloween zombies are not ‘real’; there are bacteria that can indeed generate zombies; admittedly zombie plants only. Those pathogenic bacteria are termed phytoplasmas, and they are living inside the cells of infected plants and influence plant development in a number of ways. One of the most remarkable effects of a phytoplasma infection is a reprogramming of reproductive development, such that leave-like structures instead of floral organs develop. The infected plants are sterile – they thus approach at an evolutionary dead end – and mainly serve to propagate phytoplasmas. Thus the name ‘zombie plants’ has been coined. Recently, scientist from the UK and Japan have shown that the developmental reprogramming depends on a small phytoplasma protein that interacts with plant proteins that control flower development. This interaction destines the plant proteins for degradation and causes the development of the aberrant flowers. However, it remained unclear how the interaction between the bacterial and the plant proteins evolved.'

Melzer explans how he 'cooperated with a German group and to computationally analysed the structure of the plant and phytoplasma proteins and found them to be surprisingly similar. Our analyses suggest that the phytoplasma protein underwent convergent structural and sequence evolution and may now constitute a molecular mimic for the plant protein. This mimicry is the basis of why the phytoplasma protein can interact with its plant partners and prevent them from doing their job in flower development. This way the phytoplasmas transform the host plants into ‘zombies’ that facilitate the propagation of the pathogen.'