Andreia Figueiredo, Principal Investigator at the Grapevine-Pathogen Systems Lab, at BioISI – Ciências ULisboa, and her team published a new paper, first authored by Joana Figueiredo, PhD Student from the same, in [Nature] Scientific Reports. Read this BioISI Digest and get an insight on what infection strategy is used by the grapevine-pathogenic oomycete Plasmopara viticola, known to cause a very common disease: downy mildew.
What was the starting point that led to the current research?
When looking into plant-pathogen interactions, the host extracellular space (apoplast), i.e., the space that comprises plant cell wall and the fluid in between cells, is a communication hub between the two interaction partners. In plants, the dynamics of this compartments is beginning to raise particular attention, however in grapevine it’s still a black box.
We have previously developed a methodology to extract and successfully analyze both proteome and metabolome of this compartment in grapevine. The establishment methodology was distinguished by CNOIV (Comissão Nacional da Organização Internacional da Vinha e do Vinho) this year and enabled us to gain more insights not only of its dynamics but also on the pathogen molecules that are secreted and part of its infection strategy.
What is the main finding reported in this paper?
With this work we revealed, for the first time, the in-planta proteome of the biotrophic oomycete Plasmopara viticola during its colonization process of two grapevine cultivars (susceptible and tolerant). We were able to show that P. viticola develops a specific strategy to infect susceptible or tolerant hosts. It manipulates its own phosphoinositide pathway depending on the type of interaction to improve signalling and vesicular trafficking for development and growth. During the compatible interaction, P. viticola can interfere with host salicylic acid pathway and isoprenoid biosynthesis. In contrast, in the incompatible interaction, the pathogen is activating oxidative stress protection mechanisms in a way to cope with the oxidative burst.
If you had to explain the main finding to a 5-year-old child, how would you do it?
I would say that there is a faraway land where a dragon wants to enter into a castle to steal food. In the castle there are several knights that are trying to protect it but, to be successful they need to send spies to see the dragon’s weapons and get to know its invasion strategy. Our work was really difficult because it is very hard to get near the dragon’s cavern, but we succeeded and helped the spies to get all the information they needed. With this information the knights may successfully defend their castle and protect their food.
Why is it important for the scientific community and for society at large?
Being the first communication hub between host and pathogens, unravelling the apoplast dynamics contributes deeply to improve our understanding of both partners strategies and secretomes. It also enables the identification of candidates for functional analysis and further engineering to improve host immunity. Moreover, being one of viticulture most important diseases, our work is the first that characterizes the in-planta proteome of P. viticola contributing further to our understanding of its strategies and molecules. Based on our findings, in the future, disease management alternatives might be proposed contributing to lower the amount of chemical compounds used on every growing season.
What are the next steps?
In a first instance, the next step is to understand, on the host side, the defense strategies that is established and to identify which molecules (e.g. proteins) are present in grapevine apoplast and how they are modulated in response to infection. We are already into this, and soon more news will come!
Combining all this information will enable the identification of key-players of this interaction, not only effector proteins from the pathogen side but also receptor proteins and resistance-associated proteins from the host side.
Nowadays, the introduction of resistance genes in breeding programs to improve plant defense is the most used strategy. However, for several commercial crops this approach is very time-consuming. A new and innovative alternative is focused on precise engineering of the plant immune system, through the activation of specific plant receptor domains that results in an effective immune response accompanied by a hypersensitive cell-death response. We hope that our work may contribute positively and actively for this emerging area of plant immune bioengineering, and in the end, we could help this industry to achieve a higher production sustainability.
Figure | Schematic representation of P. viticola infection strategy: the pathogen segregates the effectors (pathogen molecules) and, in response, the plant secretes molecules within the apoplastic region, which will interact with the first ones. [image provided by the authors]
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Read the full paper here.
From left to to right: Joana Figueiredo and Andreia Figueiredo [photos provided by the researchers].