14 | New Scientist | 5 February 2022
News
WHITEFLIES appear to have taken
the saying “you are what you eat”
somewhat literally. New research
suggests the tiny, herbivorous
insects have incorporated dozens
of genes from plants into their
own genome.
This volume of genes jumping
from plant to animal far exceeds
what was previously known in
insects, and may lead to new
ways to control this major pest
of fruit and vegetable crops.
When DNA is passed between
separate branches on the tree of
life, it is called horizontal gene
transfer. It is mainly known to
occur between different species
of bacteria, or between bacteria
and eukaryotic organisms – those
with cells containing membrane-
bound organelles, like animals,
plants and fungi.
In March 2021, researchers
reported the first known case of
plant-to-animal horizontal gene
transfer in silverleaf whiteflies
(Bemisia tabaci). Sometime in
their evolutionary history, the
insects acquired a single genefrom a plant they ate, which may
help them to detoxify chemical
defences produced by plants.
Separately, Florian Maumus
and Clément Gilbert, both at
the University of Paris-Saclay in
France, developed a program to
detect virus genes embedded
in the genomes of eukaryotes.
It works by using databases toidentify the species a gene comes
from, revealing foreign genetic
material mixed in with the host’s
genes. After seeing the 2021 study
on whitefly gene transfer, they
wondered if they could use their
program to find more plant
genes in the whitefly genome.
They found 50 different plant
genes that the whiteflies acquired
in 24 independent transfer events.
Based on what scientists know
about the genes most closely
related to the transferred versions,
many have some role in the plant’s
response to parasites and disease.
Many of the genes are
transcribed into RNA in the
whiteflies’ cells, which suggests
they have an active function,
although the researchers haven’t
tested their function directly
(bioRxiv, doi.org/hfdw).
Whiteflies are notorious
agricultural pests that feed
on hundreds of plant species.
Maumus thinks the adopted
genes may help the whiteflies
adapt to a wide array of hosts.
It isn’t yet clear how thesegenes are taken up by the
whiteflies, but viruses may
play a role, says Maumus, given
whiteflies are important carriers
of scores of plant viruses. The
genes may also piggyback on
other jumping genetic elements
called transposons.
“I’m quite amazed by the
number of transfer events from
plants to these insects,” says Nicky
Wybouw of Ghent University in
Belgium, adding that it is incredible
that these genes have moved
intact across kingdoms of life.
“The whole [genetic] machinery
has to still maintain its function,
and its interaction with other
proteins also has to match,” he
says. “That’s an additional layer
of complexity.”
Ted Turlings at the University
of Neuchâtel in Switzerland – part
of the team that reported the first
plant-to-whitefly gene transfer –
says the latest findings could lead
to new ways of controlling the
pests by interfering with the
genes that let them cope with
plant defences. ❚BiologyJake BuehlerNIGEL
CATT
LIN/ALAMYWhiteflies have acquired dozens
of genes from the plants they eat
A pair of silverleaf
whiteflies (Bemisia
tabaci)Solar systemURANUS and Neptune are different
shades of blue, and we may finally
know why.
In visible-light images, Uranus
appears a pale blue, while Neptune
is a deeper, cobalt hue. Using data
from the Hubble Space Telescope
and ground-based observatories,
as well as information gleaned
from the Voyager 2 spacecraft,
Patrick Irwin at the University of
Oxford and his colleagues have
developed detailed models of the
atmospheres of both worlds thatmight explain the colour difference.
The thick, enshrouding skies
of these planets are mainly made
of hydrogen and helium as well
as methane. But hazes comprising
other chemicals are thought to be
floating at different altitudes too.
These are probably created when
methane is broken down by the
sun’s ultraviolet radiation, before
reforming as larger hydrocarbons.
In their new models, the scientists
identified a haze layer, thought to
be present on both worlds, which
is roughly twice as thick on Uranus
as it is on Neptune. This feature,
which the team calls the aerosol-
layer, would look whitish at visible
wavelengths. So the greaterthickness of the aerosol-2 haze on
Uranus would lighten the planet’s
appearance – similar to how
tracing paper placed over a picture
makes its vibrant hues more milky
(arxiv.org/abs/2201.04516).“This explains why Uranus is
a paler blue colour than Neptune,”
says Irwin.
As for why the two gas giants
are blue in the first place, that
is down to the methane in their
atmospheres, says team member
Leigh Fletcher at the University
of Leicester, UK. “Methane
absorbs red light, leaving blue
to be reflected back,” he says.
Questions still remain about
the nature of darker areas on the
planets, says Naomi Rowe-Gurney
at NASA’s Goddard Space Flight
Center in Maryland. ”I am sure that
the James Webb Space Telescope
will help with this.” ❚An explanation for
the different blues of
Uranus and NeptuneWill GaterUranus (left) and Neptune,
as imaged by NASA’s
Voyager 2 spacecraftNASA
/JPL-CAL
TE
CH