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| Phytoplasma symptoms in vegetable crops. (A) Little leaf in brinjal; (B) close up view of brinjal flower showing phyllody; (C) big bud in tomato; (D) witches broom’ in Cucurbita pepo; (E) flat stem in lettuce; (F) witches’ broom in chili; (G) witches’ broom in potato; (H) witches’ broom in cabbage; and (I) flat stem in cowpea. |
Here we have yet another example of the malevolence of any creative intelligence that can come up with so much of nature. In this case we have a type of obligate, endoparasitic bacterium that lives in plant cells and prevents the plant from reproducing while the plant supports bacterial reproduction, in what has been termed 'zombification' - where a parasite converts the host to work for it, often against its own interests.
This pathogen is currently imposing a major economic burden on those least able to bear it - third-world farmers.
Two teams of researchers have worked to explain exactly how this bacterium works. The Lipmann Insitute press release explains:
Phytoplasma are a type of bacteria that live within the cells and cause devastating diseases with damaging effects. For example, in many cases plants infected with phytoplasma are no longer able to develop flowers. These plants have actually been described as "zombies," since they allow the reproduction of phytoplasma but are unable to reproduce themselves anymore. A group of biologists based at Friedrich Schiller University and the Fritz Lipmann Institute in Germany are working to help better understand exactly how phytoplasma cells bring about the so-called zombification of plants.
"Our group has been studying the proteins that are targeted by the phytoplasma effector proteins for almost 30 years," said Günter Theißen, one of the scientists involved in the study. "In our latest research, based on just few data and some simple assumptions, we predicted the structure of the respective effector protein (termed SAP54) about 5 years ago. With the new work, we tested our hypothesis experimentally, and found that our prediction was quite accurate."
Phytoplasma cells bring about devastating changes in plants by secreting effector proteins that interact with some molecules of the plant host, which leads to developmental abnormalities. This interaction is very specific as only very special host molecules are recognized by the phytoplasma effector molecules.
"This specificity is achieved by the effector proteins adopting a special structure that somewhat mimics part of the structure of the host molecules bound," explained Theißen. "This way, structural analyses at the molecular level help explain an important group of plant diseases."
Almost simultaneously, two other groups of scientists determined the crystal structure of very similar and highly related proteins, providing strong confirmation of the findings of Theißen and his colleagues. The team at Friedrich Schiller University also found that the effector protein SAP54 binds better to multimeric complexes of the target proteins than to protein dimers (pairs of proteins), suggesting an exciting avenue for future research.
"We are doing basic research," said Theißen. "However, there is no effective cure for phytoplasma infections that can be used in agronomy yet so, for example, when an orchard is affected, the only solution is to cut down all the infected trees, with dramatic economic ramifications. We hope that the more we know about how phytoplasma cells affect their hosts, the more we can help avoid the damage." [My emphasis]
Their findings were published last July in Molecular Plant-Microbe Interactions®:
Abstract
Phytoplasmas are intracellular bacterial plant pathogens that cause devastating diseases in crops and ornamental plants by the secretion of effector proteins. One of these effector proteins, termed SECRETED ASTER YELLOWS WITCHES’ BROOM PROTEIN 54 (SAP54), leads to the degradation of a specific subset of floral homeotic proteins of the MIKC-type MADS-domain family via the ubiquitin-proteasome pathway. In consequence, the developing flowers show the homeotic transformation of floral organs into vegetative leaf-like structures. The molecular mechanism of SAP54 action involves binding to the keratin-like domain of MIKC-type proteins and to some RAD23 proteins, which translocate ubiquitylated substrates to the proteasome. The structural requirements and specificity of SAP54 function are poorly understood, however. Here, we report, based on biophysical and molecular biological analyses, that SAP54 folds into an α-helical structure. Insertion of helix-breaking mutations disrupts correct folding of SAP54 and compromises SAP54 binding to its target proteins and, concomitantly, its ability to evoke disease phenotypes in vivo. Interestingly, dynamic light scattering data together with electrophoretic mobility shift assays suggest that SAP54 preferentially binds to multimeric complexes of MIKC-type proteins rather than to dimers or monomers of these proteins. Together with data from literature, this finding suggests that MIKC-type proteins and SAP54 constitute multimeric α-helical coiled coils. Our investigations clarify the structure-function relationship of an important phytoplasma effector protein and may thus ultimately help to develop treatments against some devastating plant diseases.
Reprinted from: Aurin, Marc-Benjamin; Haupt, Michael; Görlach, Matthias; Rümpler, Florian; Theißen, Günter
Structural Requirements of the Phytoplasma Effector Protein SAP54 for Causing Homeotic Transformation of Floral Organs
Molecular Plant-Microbe Interactions® 2020 33(9) pp 1129-1141 DOI 10.1094/MPMI-02-20-0028-R
© 2020 The authors
Published by The American Phytopathological Society (APS)
If we accept the arguments put forward by Intelligent [sic] Design advocates, we have to assume that any omniscient intelligence knew exactly what it was designing and exactly what it would do, and deliberately designed it for that purpose. In this case, the purpose appears to have been two-fold:
- To kill plants and devastate crops
- To make more bacteria so they can kill more plants and devastate more crops.
As always with these examples, I would love to hear from a creationist how they explain that the only explanation for these abundant examples of malevolence from nature that doesn't leave their assumed creator looking like a malevolent, pestilential sadist is the entirely natural process of evolution. I don't expect to get any rational answers.
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