How plants distinguish beneficial from harmful microbes

Date:
August 7, 2020
Source:
Aarhus University
Summary:
Plants recognize beneficial microbes and keep harmful ones out,
which is important for healthy plants production and global food
security.

Scientists have now discovered how legumes use small, well-defined
motifs in receptor proteins to read molecular signals produced by
both pathogenic and symbiotic microbes. These remarkable findings
have enabled the researchers to reprogram immune receptors into
symbiotic receptors, which is the first milestone for engineering
symbiotic nitrogen-fixing symbiosis into cereal crops.



FULL STORY ========================================================================== Legume plants fix atmospheric nitrogen with the help of symbiotic
bacteria, called Rhizobia, which colonize their roots. Therefore, plants
have to be able to precisely recognize their symbiont to avoid infection
by pathogenic microbes. To this end, legumes use different LysM receptor proteins located on the outer cell surface of their roots. In the study published in Science, an international team of researchers led by Aarhus University show that pathogenic (chitin) or symbiotic signalling molecules
(Nod factors) are recognized by small molecular motifs on the receptors
that direct the signalling output towards either antimicrobial defence
or symbiosis.


==========================================================================
All land plants have LysM receptors that ensure detection of various
microbial signals, but how a plant decides to mount a symbiotic or an
immune response towards an incoming microbe is unknown. "We started by
asking a basic and, maybe at start, nai"ve question: Can we identify the important elements by using very similar receptors, but with opposing
function as background for a systematic analysis?" says Zolta'n
Bozsoki. "The first crystal structure of a Nod factor receptor was a breakthrough. It gave us a better understanding of these receptors and
guided our efforts to engineer them in plants." Kira Gysel adds.

The study combines the structure-assisted dissection of defined regions
in LysM receptors for biochemical experiments and in planta functional analysis. "To really understand these receptors, we needed to work
closely together and combine structural biology and biochemistry with
the systematic functional tests in plants," says Simon Boje Hansen. By
using this approach, the researchers identified previously unknown motifs
in the LysM1 domain of chitin and Nod factor receptors as determinants
for immunity and symbiosis. "It turns out that there are only very few,
but important, residues that separate an immune from a symbiotic receptor
and we now identified these and demonstrate for the first time that it
is possible to reprogram LysM receptors by changing these residues,"
says Kasper Ro/jkjaer Andersen.

The long-term goal is to transfer the unique nitrogen-fixing ability that legume plants have into cereal plants to limit the need for polluting commercial nitrogen fertilizers and to benefit and empower the poorest
people on Earth. Simona Radutoiu concludes, "We now provide the conceptual understanding required for a stepwise and rational engineering of LysM receptors, which is an essential first step towards this ambitious goal."

========================================================================== Story Source: Materials provided by Aarhus_University. Original written
by Lisbeth Heilesen.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Zoltan Bozsoki, Kira Gysel, Simon B. Hansen, Damiano Lironi,
Christina
Kro"nauer, Feng Feng, Noor De Jong, Maria Vinther, Manoj Kamble,
Mikkel B. Thygesen, Ebbe Engholm, Christian Kofoed, Se'bastien Fort,
John T.

Sullivan, Clive W. Ronson, Knud J. Jensen, Mickae"l Blaise,
Giles Oldroyd, Jens Stougaard, Kasper R. Andersen, Simona
Radutoiu,. Ligand- recognizing motifs in plant LysM receptors
are major determinants of specificity. Science, 2020 DOI:
10.1126/science.abb3377 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200807093758.htm

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