Plants use a blend of external influences to evolve defense mechanisms


Date:
June 15, 2021
Source:
eLife
Summary:
Plants evolve specialized defense chemicals through the combined
effects of genes, geography, demography and environmental
conditions.



FULL STORY ========================================================================== Plants evolve specialised defence chemicals through the combined effects
of genes, geography, demography and environmental conditions, a study
published today in eLife reports.


==========================================================================
The findings reveal a pattern in the types of defence chemicals plants
produce across Europe, and describe some of the evolutionary processes
that create them.

As plants are immobile organisms, they rely on producing defence
chemicals called specialised metabolites for survival. Specialised
metabolites have extensive variation in their structure, such as the
number of carbon molecules and the other chemical groups that attach to
those carbon molecules. Each plant under each environment has a unique
profile of specialised metabolites as a result of genetic variation that
has developed over years by different evolutionary processes and events.

"We already know that environmental pressures such as the type of
herbivores that prey on plants influences the specialised metabolites
plants produce," explains first author Ella Katz, Postdoctoral Researcher
at the Department of Plant Sciences, University of California, Davis,
US. "We wanted to understand how the intersection of environmental
pressure, demography and genomic complexity gives rise to the pattern
of metabolic variation across a plant species." To do this, the team
measured the variation in specialised metabolites across a population
of almost 800 seed samples of the plant species Arabidopsis thaliana
(A. thaliana) -- a type of cress -- taken from across Europe.

They looked at three locations in the plant genome known to influence A.

thaliana's survival fitness as well as across the entire genome to
find genes linked to metabolite production. They then grouped each
gene into classes representing types of specialised metabolite,
called chemotypes. This allowed them to see which chemotypes were
most prevalent in different regions of Europe and reveal specific
geographic patterns. For example, in central Europe and parts of Northern Europe, such as Germany and Poland, there was large variability in the chemotypes. But in southern Europe, including the Iberian Peninsula,
Italy and the Balkan, there were two predominant chemotypes that were
clearly geographically separated.

Next, they looked at whether these geographical differences in chemotypes
were linked to weather and landscape conditions. They assigned each gene
an environmental value based on its location -- such as distance to the
coast, rainfall in the wettest and driest months, and temperature of the warmest and coldest months. They also assigned the genes to Northern or Southern locations, based on their position relative to the Pyrenees, Alps
or Carpathian mountain ranges. Using the most commonly found chemotypes,
they showed that the environmental conditions had different relationships
to the chemotypes that shift by geographical area. This suggests that the relationship between environmental conditions and specialised metabolites varies across different regions in Europe -- so, even if wetter weather
was linked to a certain chemotype in Southern Europe, this was not the
same in Northern Europe.

Finally, they looked at how these genes evolved over time. Gene traits
can evolve either independently within a species, called convergent
evolution, or by parallel evolution, where species respond to similar
external challenges in a similar way. They found that gene evolution at
the three most common genome locations was shaped by a blend of events reminiscent of either parallel or convergent evolution. Moreover, the
presence of variation at each of the three locations also plays a role
in further shaping the evolution of the other genes. This is most likely because the effects of different specialised metabolites may work with
or against each other to help the plant survive.

"Our work provides a new perspective on the complexity of the forces and mechanisms that shape the generation and distribution of specialised metabolites and affect the plant's ability to survive in a changing environment," concludes senior author Daniel Kliebenstein, Professor
at the Department of Plant Sciences, University of California, Davis,
and the DynaMo Center of Excellence, University of Copenhagen,
Denmark. "Using a larger plant population from other locations
around the world will enable us to deepen our understanding of the
evolutionary mechanisms that determine the variation in a population." ========================================================================== Story Source: Materials provided by eLife. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Ella Katz, Jia-Jie Li, Benjamin Jaegle, Haim Ashkenazy, Shawn
R Abrahams,
Clement Bagaza, Samuel Holden, Chris J Pires, Ruthie Angelovici,
Daniel J Kliebenstein. Genetic variation, environment and demography
intersect to shape Arabidopsis defense metabolite variation across
Europe. eLife, 2021; 10 DOI: 10.7554/eLife.67784 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/06/210615132100.htm

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