Plant root-associated bacteria preferentially colonize their native
host-plant roots

Date:
July 26, 2021
Source:
Max Planck Institute for Plant Breeding Research
Summary:
Researchers have discovered that bacteria from the plant microbiota
are adapted to their host species. They show how root-associated
bacteria have a competitive advantage when colonizing their native
host, which allows them to invade an already established microbiota.



FULL STORY ==========================================================================
An international team of researchers from the Max Planck Institute for
Plant Breeding Research and the University of AAarhus in Denmark has
discovered that bacteria from the plant microbiota are adapted to their
host species. In a newly published study, they show how root-associated bacteria have a competitive advantage when colonizing their native host,
which allows them to invade an already established microbiota.


========================================================================== Plants, including crops such as rice and wheat, obtain their essential
mineral nutrients and water through their roots, making them an important interface between plants and the soil environment. The roots of land
plants associate with a wide range of microbes -- including bacteria --
that are recruited from the surrounding soil and assemble into structured communities known as the root microbiota. These microbial communities are sustained by the plant host, which provides them with nutrients, primarily
in the form of organic carbon compounds secreted by the root. In turn,
these commensal bacteria mediate multiple processes that are beneficial to their plant host, such as providing defense against pathogens, improving nutrient mobilization from the soil and positively impacting growth.

Given their importance for plant health, the study of the root microbiota
has evolved into a promising research field that aims to understand how
these interactions occur, and could eventually help increase the yield
and resilience of crop plants. Although it is well known that plants
secrete diverse small molecules into the soil via their roots that serve
as chemoattractants for root colonization by a subset of soil-dwelling bacteria, the degree of active selection performed by the host and the
extent to which root-associated microbial communities are adapted to
specific plant species remain largely unknown. In a new study published
in Nature Microbiology, a team of researchers from the Department of Plant-Microbe Interactions at the MPIPZ in Cologne, Germany, and AArhus University in Denmark, aimed to gain a deeper understanding of these
complex multi-species interactions.

As a first step in this quest, they established a comprehensive collection
of root-derived bacteria from the model legume Lotus japonicus, a small proportion of which are symbiotic bacteria that fix atmospheric nitrogen
for plant growth.

Together with an already established culture collection from roots of
the model crucifer Arabidopsis thaliana, synthetic microbial communities (SynComs) were designed to explore the microbiota assembly of different
plant species.

Although the bacterial communities of the two plants were similar,
the researchers observed a clear preference by these bacteria to
colonize their native host. This preference was mediated by a higher competitiveness displayed by multiple bacterial species when colonizing
their host of origin compared to those originally isolated from the
other host.

Strikingly, host preference was only observed in a community context,
where different microbes compete among each other, but not when individual bacterial species were allowed to colonize the plant roots in the absence
of competition.

Analysis of gene expression of both plant species when interacting with different synthetic communities further showed that this process was
at least in part driven by the host. Intriguingly, root colonization
by native and non- native SynComs exhibited contrasting gene expression profiles for a number of well-known regulators of plant immunity. Based on
this observation, the authors then hypothesized that native strains have
a competitive advantage when colonizing the roots of their corresponding
host plant via the formation of species-specific host niches. To test
this hypothesis, the scientists performed a series of complex experiments, where SynComs from different host species were allowed to invade already established root-associated bacterial communities in host and non-host
plants. Their results showed that native SynComs had a competitive
advantage when invading an already established microbiota in their host
plant, indicating that adaptation of commensal bacteria to their native
plant species leads to increased invasiveness and persistence.

To quote Kathrin Wippel, first author of the study: "We were amazed
to learn that root colonization by native and non-native SynComs
resulted in differential transcriptional reprogramming of plant roots,
possibly contributing to the formation of specific root niches for native commensal bacteria. These findings indicate that diverse soil-dwelling
bacteria associate with and prefer a specific host plant, similar to
pathogens or beneficial symbionts of plants." These findings could have
a meaningful impact on agriculture, as they highlight the importance
of competitiveness between different bacteria and the impact of host
preference for successful root colonization. Probiotic inoculants tailored
to specific crop plants with an enhanced capacity to invade and persist
in standing microbial communities could help overcome the variation in
efficacy of currently used biologicals in agriculture.

========================================================================== Story Source: Materials provided by Max_Planck_Institute_for_Plant_Breeding_Research. Note: Content may be
edited for style and length.


========================================================================== Journal Reference:
1. Kathrin Wippel, Ke Tao, Yulong Niu, Rafal Zgadzaj, Niklas Kiel,
Rui Guan,
Eik Dahms, Pengfan Zhang, Dorthe B. Jensen, Elke Logemann,
Simona Radutoiu, Paul Schulze-Lefert, Ruben Garrido-Oter. Host
preference and invasiveness of commensal bacteria in the Lotus
and Arabidopsis root microbiota. Nature Microbiology, 2021; DOI:
10.1038/s41564-021-00941-9 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/07/210726113938.htm

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