Gene mutation regulates plant responses to biotic stress

At times, scientists initiate their studies and find exactly what they had been looking for, while sometimes they end up with something unanticipated.

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A similar case happened when a team of researchers analyzing the stress responses of plants came across a new mutation.

The discovery of this mutation was actually a surprise. And by trying to better understand this new mutation, and what effect it had on plant stress responses, we uncovered new information about how different plant stress regulators function.”

Matt Neubauer, Study First Author, American Phytopathological Society

When the researchers were working on a stress regulating gene called Enhanced Disease Resistance1 (EDR1), they detected a new gain-of-function mutation in a second gene called Phytoalexin Deficient4 (PAD4)—a gene that controls the responses of plants to biotic stress.

PAD4 has been studied for a long time, but this is the first time a gain-of-function mutation has been identified. We named this mutation pad4-13. It occurred as a spontaneous mutation in the edr1-mutant background and enhances cell death during fungal infection. We believe it was selected during backcrossing of the original edr1 mutant because it enhances the visible edr1 mutant phenotype, powdery mildew-induced cell death.”

Matt Neubauer, Study First Author, American Phytopathological Society

The researchers also discovered that this mutation renders the PAD4 protein more active, which consequently allows the plants to exhibit a response that resists pathogenic infections more strongly.

This was found to be unique because the pad4 mutations discovered earlier are essentially loss-of-function and render the plants more sensitive to fungal, oomycete, and bacterial pathogens.

The researchers also identified another crucial detail about the plant stress regulators. It has been determined that the PAD4 protein communicates with a partner protein called EDS1, which stands for Enhanced Disease Susceptibility, to switch on the plant stress responses.

By performing this study, the researchers discovered that EDR1 blocks the PAD4 protein from communicating with the EDS1 protein, which may offer a way to dampen or switch off the stress responses.

The discovery that EDR1 may directly regulate PAD4 enhances our knowledge of how plants control stress responses. Ultimately we were unable to show how this new mutation makes PAD4 more active.”

Matt Neubauer, Study First Author, American Phytopathological Society

Neubauer admitted that there is still more to learn.