Dodder uses the flowering signal of its host plant to flower

Date:
August 31, 2020
Source:
Max Planck Institute for Chemical Ecology
Summary:
Researchers have investigated how the parasitic dodder Cuscuta
australis controls flower formation. They showed that the parasite
eavesdrops on the flowering signals of its host plants in order to
activate its own flowering machinery. By synchronizing flowering
with its host plant, the parasite makes sure that it can grow on
its host long enough to produce the optimal amount of seeds.



FULL STORY ==========================================================================
The plant genus Cuscuta consists of more than 200 species that can
be found almost all over the world. The parasites, known as dodder,
but also called wizard's net, devil's hair or strangleweed, feed on
other plants by attaching themselves to their hosts via a special
organ, the haustorium, and withdrawing nutrients from them. They have
neither roots nor leaves. Without leaves, they are hardly able to photosynthesize. Without roots they cannot absorb nutrients and water
from the soil. On the other hand, they are integrated into the internal communication network of their host plants and can even pass on warning
signals from plant to plant.


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A team of scientists led by Jianqiang Wu, who has been the leader of a Max Planck Partner Group at the Kunming Institute of Botany, Chinese Academy
of Sciences, now asked how the parasites manage to synchronize flowering
with their hosts. They had observed that plants of the Australian dodder (Cuscuta australis) adjusted the time of their flowering to that of
their respective host plant species.

Flower promoting signal FT from the host also determines the flowering
time of the parasite "The flowering time is controlled by leaves, as
leaves can sense environmental cues and synthesize the flowering signal,
a protein named FLOWERING LOCUS T (FT), which travels through the plant vascular system. We therefore wondered how a leafless parasite such
as Cuscuta australis controls the timing of its flowering," says lead investigator Jianqiang Wu. In 2018, his team had sequenced the genome
of C. australis and found that many genes important for regulation of
flowering time were lost in C. australis genome. Therefore, C.

australis seems to be unable to activate its own flowering mechanism.

Based on the fact that FT proteins are mobile signals, the researchers hypothesized that dodder eavesdrops on the flowering signals produced by
the leaves of its host and uses them for producing its own flowers. To
prove this eavesdropping scenario, they used genetically modified host
plants in which the expression of FT genes had been altered, and this
indeed affected the flowering time of the parasite. They also coupled
the FT protein to a green fluorescent protein (GFP) as a tag and detected
the host plant's flower promoting signal in the parasite: The tagged FT
protein had migrated from host to parasite.

For dodder, it is the best strategy to synchronize flowering with that
of its host. If it flowers much later than its host does, it may not be
able to produce seeds at all, as the nutrients in the host are rapidly
drained by the host's reproductive tissues. The host may even rapidly
die before the parasite can even starts to produce seeds. However, if
dodder flowers too early, its growth is likely prematurely ended and
it may not be able to produce as many seeds as the dodder plants whose flowering time is synchronized with that of their hosts.

Regressive Evolution: Gene loss as an advantage In the course of
evolution, plant parasites have lost certain traits and "outsourced" physiological processes. As a result, various genes in their genomes
may be lost. "This work establishes that for a plant parasite, losing
control over flowering processes can be advantageous, as it allows the
parasite to hijack its host's mobile flowering signals for its own use. It
can thereby readily synchronize its physiology with that of its host,"
says co-author Ian Baldwin, director of the Department Molecular Ecology
at the Max Planck Institute for Chemical Ecology. Because of the gene
loss, dodder may be able to better adapt to the parasitic lifestyle and ultimately increase its fitness.


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


========================================================================== Journal Reference:
1. Shen, G., Liu, N., Zhang, J., Xu, Y., Baldwin, I. T., Wu, J. Cuscuta
australis (dodder) parasite eavesdrops on the host plants' FT
signals to flower. Proceedings of the National Academy of Sciences,
2020 DOI: 10.1073/pnas.2009445117 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200831154410.htm

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