Researchers at GMI – Mendel Institute of Molecular Plant Biology of the Austrian Academy of Sciences, the University of North Carolina at Chapel Hill and therefore the Hughes Medical Institute (HHMI) use two complementary approaches to unveil a co-evolutionary mechanism between bacteria and plants and also explain complex immune reaction patterns observed within the wild. Together the papers change the way scientists are brooding about the connection of a bacterial antigenic component with its plant immune receptor. the 2 papers are published back to back within the journal Cell Host & Microbe.
Immune responses have developed in virtually all organisms over evolutionary time scales to guard them from foreign invaders. A central aspect of the immune reaction of upper organisms, i.e., plants and animals, is that the use of sensory systems that detect and answer “non-self” molecular signals. These molecular signals generally determine the survival chances of the pathogen, an element that forestalls them from being eliminated by survival as a way to evade host recognition. Their evolutionary conservation is thus thanks to the functionality of those molecular signals to the foreign invader. However, the negative evolutionary pressure to take care of this functionality is counterbalanced by the positive evolutionary pressure to mediate the pathogen’s immune evasion. The dissection of those co-evolutionary forces through synthetic and reverse evolutionary methods is one among the 2 research approaches that researchers from the Belkhadir lab at GMI and therefore the Dangl lab at UNC- Chapel Hill team to research . In an orthogonal approach, they also discuss the natural diversity of molecular antigenic determinants (epitopes) in plant-colonizing bacterial communities (commensal communities) and map the complex immune reaction patterns they trigger within the plants. Jeffery Dangl, John N. Couch Distinguished Professor at UNC-Chapel Hill and an HHMI investigator explains: “To date, most science during this field has used a couple of epitopes. We sampled thousands, derived from synthetic biology and commensal communities. This depth of study allowed us to uncover an upscale diversity of host response mediated by one receptor.”
Reverse evolution and new insights on co-evolution
The researchers examine how the Arabidopsis immune sensor FLS2 (flagellin sensing 2) influenced the evolution of its interacting epitope on the Pseudomonas flagellin, and the way this, in turn, influenced Pseudomonas motility. Using reverse evolutionary methods, Parys et al. uncover a replacement mechanism of co-evolutionary force between FLS2 and flagellin, and frame it as a molecular sort of the scarcely studied theory of antagonistic pleiotropy (AP) in plant immunology. AP is that the ability of a gene to induce opposing effects in several contexts, a prevailing theory for the evolutionary origin of aging in humans. The researchers demonstrate that AP fosters stable colonization of Arabidopsis by commensal communities by weighing out bacterial motility against sensor detection. This strategy leads to flagellin epitopes that either mildly activate or outright block the receptor (gain in virulence), while losing in motility as a trade-off (loss in virulence). Even more excitingly, they find signatures of those synthetic experiments in present commensal communities, suggesting that natural microbiomes could be less hooked in to flagella-mediated motility and willing to trade it off against another sort of immune evasion so as to remain consonant with the plant.
Friend or foe?
In the second, natural sampling approach, Colaianni et al. demonstrate that immune evasion mechanisms in plant root commensal communities are rampant and are a determining factor of the community’s structure. Moreover, this conceptual breakthrough is amid the corroborating findings of complex immune reaction fine-tuning mechanisms in Arabidopsis. the range of the ligand epitopes is translated during a complexity of the immune responses engaged by the plant, which is capable of detecting threshold variations in its microbiome, and thus, discriminating between “friend and foe.”On immune evasion and plant growth promotionAsked about possible applications of this joint work, GMI group leader Youssef Belkhadir elaborates: “Sometimes, it’s good to understand the way to activate an immune reaction , but we frequently forget that, sometimes, it’d even be good to show it off. for instance , you’ll help a growth-promoting microbe better colonize the plant by providing it with a further thanks to evade the plant’s immune reaction . And here we discovered synthetic antagonistic peptides that would do exactly that.”
On immune evasion and plant growth promotion
This collaboration draws on an exchange in expertise between the alternating first authors of the 2 publications, but also refreshes long-dating, outstanding, scientific contacts. In fact, Nicholas Colaianni, Ph.D. student within the Dangl lab at UNC-Chapel Hill, may be a computational expert, whereas the most fields of experience of Katarzyna Parys (former Ph.D. student within the Belkhadir lab) dwell biochemistry and wet lab genetics. Colaianni also visited the Belkhadir lab at GMI and both he and Parys benefited from hands-on training in each other’s field of experience . additionally , as a 3rd co-first author on both publications, Ho-Seok Lee, postdoctoral fellow within the Belkhadir lab, contributed his skills in microscopy imaging.
After a few years of separate research, the 2 main principal investigators who share seniority and alternate corresponding authorships on the 2 publications, decided to form a comeback together. The shared seniority also includes Corbin Jones, Biology Professor at UNC-Chapel Hill and Colaianni’s co-mentor. Youssef Belkhadir may be a UNC-Chapel Hill alumnus who worked with Jeffery Dangl as a Ph.D. student. pertaining to the UNC Tar Heels five that Dangl loves, Belkhadir says “17 years after I co-authored my first paper with Jeff, it had been tons of fun to urge on the court and ‘slam-dunk’ it with him once more!”. Dangl adds “Just like basketball, science may be a team effort and therefore the best teams play fluidly together.”
An international consortium
GMI and UNC-Chapel Hill share a deep commitment to international collaboration and therefore the present work rallied a world consortium of scientists spearheaded by Youssef Belkhadir, including the University of Geneva and therefore the University of Lausanne in Switzerland, the Perutz Labs of the University of Vienna in Austria and therefore the University of Würzburg in Germany. The researchers also acknowledge the contribution of the Vienna Biocenter member institutes and facilities.