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Ancient defence strategy continues to protect plants from pathogens

ta385 — Fri, 12 Jul 2019 07:30:00 +0000

Researchers from the Sainsbury Laboratory at the ̽��ֱ�� of Cambridge compared how two distantly related plants – a common liverwort (Marchantia polymorpha) and a flowering plant, wild tobacco (Nicotiana benthamiana) – defend themselves against an aggressive pathogen (Phytophthora palmivora).

This is the first time such a comparison has been undertaken. By studying how these distantly related plants – which split from their common ancestor roughly 400 million years ago – respond to pathogen infections, the research team discovered a suite of microbe-responsive gene families that date back to early land plant evolution.

Our current understanding of how plants successfully defend against disease-causing pathogens mainly originates from studying economically important crop plants and a small number of closely-related flowering plant model systems. Very distantly-related plants, such as non-flowering liverworts that are believed to resemble some of the first land plants, are often overlooked. As a result, not much was known about how these plants defend themselves from pathogens or how plant defence strategies have evolved.

Published in Current Biology, the study's identification of these evolutionarily conserved genes is shedding new light on the strategies that were likely critical for the expansion of plants onto land.

“We have shown that molecular responses to pathogen infection typical of modern flowering plants are common to very distantly-related land plants and may therefore be more ancient than we previously thought,” said Dr Sebastian Schornack, who led the research team that undertook the study. “Despite fluctuating environmental pressures over a broad evolutionary timescale, these conserved genes have retained their capacity to confer pathogen protection in plants, including in important agricultural crops.”

Bioinformatics expert, Dr Anna Gogleva, identified a subset of one-to-one corresponding genes (single-copy orthologs) in the liverwort and wild tobacco and analysed their level of activity during the infection. A number of different genes were activated in both plants, but a set of metabolic genes involved in phenylpropanoid (flavonoid) biosynthesis were highly activated in response to infection.

These gene families are often associated with the stress-response in flowering plants, providing increased protection against biotic or abiotic stresses caused by chewing insects, pathogens and nutrient or light stress. However, this was the first time that these genes had been functionally linked to pathogen defence strategies in liverworts.

“Pathogen zoospores germinate on the surface of liverworts and eventually colonise the liverwort tissues, but in some areas we saw an accumulation of a purple/red pigment in the liverwort tissues where the pathogen was rarely detected,” said Dr Philip Carella, lead author of the study.

“We produced liverwort plants with mosaic pigment patterns – resembling military camouflage fatigues – that allowed us to compare pathogen resistance in pigmented and non-pigmented areas of the same plant and found the pigment provided some resistance to pathogen infection.”

̽��ֱ��enormous diversity of traits and species that we see in modern plants today speaks to the millions of years of evolution that enabled plants to survive in dynamic and contrasting environments across the globe.

“ ̽��ֱ��conflict between organisms can be a very powerful selective pressure that guides their evolutionary trajectory,” said Dr Schornack. “Genes involved in fighting specific pathogens can evolve rapidly – both in plants and animals. But we have also now found these broadly-conserved genes responding to pathogen infection in very distantly-related plants, which suggests that land plants have retained a likely ancient pathogen deterrence strategy that is much too useful to lose.

“Fossil evidence shows that plants have engaged in close-interactions with microbial life forms throughout their evolutionary history. Our research has uncovered a common set of pathogen-responsive genes shared in early-divergent land plants and more evolutionarily young flowering plants, which are all likely to have been critical for the expansion of plants onto land. Further comparative studies focusing on other distantly related land plants and their aquatic algal predecessors should reveal even more information about the evolution and role of these vital gene families.”

Reference

Philip Carella, Anna Gogleva, David John Hoey, Anthony John Bridgen, Sara Christina Stolze, Hirofumi Nakagami, and Sebastian Schornack. Conserved Biochemical Defenses Underpin Host Responses to Oomycete Infection in an Early-Divergent Land Plant Lineage. Current Biology (11 July 2019); DOI: 10.1016/j.cub.2019.05.078

Scientists at the ̽��ֱ�� of Cambridge have uncovered striking similarities in how two distantly related plants defend themselves against pathogens despite splitting from their common ancestor more than 400 million years ago.

Land plants have retained a likely ancient pathogen deterrence strategy that is much too useful to lose

Sebastian Schornack

̽��ֱ��Sainsbury Laboratory, ̽��ֱ�� of Cambridge

Sebastian Schornack and Philip Carella of the Sainsbury Laboratory, ̽��ֱ�� of Cambridge

Funding

This work was funded by the Gatsby Charitable Foundation, the Royal Society, the BBSRC OpenPlant initiative, the Natural Environment Research Council (NERC; NE/N00941X/1), and a Natural Sciences and Engineering Research Council of Canada (NSERC) postdoctoral fellowship to Philip Carella. Proteomic work performed in the Nakagami lab was supported by the Max-Planck-Gesellschaft.

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Research shows first land plants were parasitised by microbes

Anonymous — Wed, 04 Apr 2018 08:42:38 +0000

Why do some plants welcome some microbes with open arms while giving others the cold-shoulder? Like most relationships, it’s complicated, and it all goes back a long way. By studying liverworts – which diverged from other land plants early in the history of plant evolution – researchers from the Sainsbury Laboratory at the ̽��ֱ�� of Cambridge have found that the relationship between plants and filamentous microbes not only dates back millions of years, but that modern plants have maintained this ancient mechanism to accommodate and respond to microbial invaders.

Liverworts Liverworts are small green plants that don’t have roots, stems, leaves or flowers. They belong to a group of plants called Bryophytes, which also includes mosses and hornworts. Bryophytes diverged from other plant lineages early in the evolution of plants and are thought to be similar to some of the earliest diverging land plant lineages. Liverworts are found all over the world and are often seen growing as a weed in the cracks of paving or soil of potted plants. Marchantia polymorpha, which is also known as the common liverwort or umbrella liverwort, was used in this research.

Published today in the journal Proceedings of the National Academy of Sciences, a new study shows that aggressive filamentous microbial (fungi-like) pathogens can invade liverworts and that some elements of the liverwort’s response are shared with distantly related plants. ̽��ֱ��first author of the paper, Dr Philip Carella, said the research showed that liverworts could be infected by the common and devastating microorganism Phytophthora: “We know a great deal about microbial infections of modern flowering plants, but until now we haven’t known how distantly related plant lineages dealt with an invasion by an aggressive microbe. To test this, we first wanted to see if Phytophthora could infect and complete its life cycle in a liverwort."

Above image: A healthy Marchantia polymorpha liverwort (left) and one that has been infected by Phytophthora palmivora (right).

"We found that Phytophthora palmivora can colonise the photosynthetic tissues of the liverwort Marchantia polymorpha by invading living cells. Marchantia responds to this by deploying proteins around the invading Phytophthora hyphal structures. These proteins are similar to those that are produced in flowering plants such as tobacco, legumes or Arabidopsis in response to infections by both symbiont and pathogenic microbes.”

Above image: Microscopy image of a cross-section of a Marchantia polymorpha thallus showing the Phytophthora infection (red) in the upper photosynthetic layer of the liverwort plant.

These lineages share a common ancestor that lived over 400 million years ago, and fossils from this time period show evidence that plants were already forming beneficial relationships with filamentous microbes. Dr Carella added: “These findings raise interesting questions about how plants and microbes have interacted and evolved pathogenic and symbiotic relationships. Which mechanisms evolved early in a common ancestor before the plant groups diverged and which evolved independently?”

Phytophthora Phytophthora is a water mould. Although it looks like it, it is not a fungus at all. Instead it belongs to the oomycetes and is a type of filamentous microbe. Phytophthora pathogens are best known for devastating crops, such as causing the Irish potato famine through potato late blight disease as well as many tropical diseases. This research used the tropical species, Phytophthora palmivora, which causes diseases in cocoa, oil palms, coconut palms and rubber trees.

Dr Sebastian Schornack, who led the research team, says the study indicates that early land plants were already genetically equipped to respond to microbial infections: “This discovery reveals that certain response mechanisms were already in place very early on in plant evolution.”

“Finding that pathogenic filamentous microbes can invade living liverwort cells and that liverworts respond using similar proteins as in flowering plants suggests that the relationship between filamentous pathogens and plants can be considered ancient. We will continue to study whether pathogens are exploiting mechanisms evolved to support symbionts and, hopefully, this will allow us to establish future crop plants that both benefit from symbionts while remaining more resistant to pathogens. “Liverworts are showing great promise as a model plant system and this discovery that they can be colonised by pathogens of flowering plants makes them a valuable model plant to continue research into plant-microbe interactions.”

This research was funded by the Gatsby Charitable Foundation, the Royal Society, the BBSRC OpenPlant initiative and the Natural Environment Research Council.

Relationship between plants and filamentous microbes not only dates back millions of years, but modern plants have maintained this ancient mechanism to accommodate and respond to microbial invaders.

Research shows first land plants were parasitised by microbes

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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