Pesticides can protect crops from hydrophobic pollutants
Effectiveness demonstrated in the Cucurbitaceae family

Date:
July 28, 2020
Source:
Kobe University
Summary:
Researchers have revealed that commercial pesticides can be applied
to crops in the Cucurbitaceae family to decrease their accumulation
of hydrophobic pollutants, thereby improving crop safety. The team
developed two approaches to control the functions of plant proteins
related to the transport of hydrophobic pollutants. These findings
will lead to these new functions of pesticides being utilized in
agriculture, enabling safer crops to be produced.



FULL STORY ========================================================================== Researchers have revealed that commercial pesticides can be applied
to crops in the Cucurbitaceae family to decrease their accumulation
of hydrophobic pollutants (*1), thereby improving crop safety. The
research group consisted of FUJITA Kentaro (1st year Ph.D. student)
of Kobe University's Graduate School of Agricultural Science, Academic Researcher YOSHIHARA Ryouhei (now an assistant professor at Saitama
University) and Associate Professor INUI Hideyuki of Kobe University's Biosignal Research Center, Senior Research Scientist KONDOH Yasumitsu, Technical Staff HONDA Kaori and Group Director OSADA Hiroyuki of RIKEN,
and Lead Researcher HAGA Yuki and Senior Scientist MATSUMURA Chisato of
Hyogo Prefectural Institute of Environmental Sciences.


==========================================================================
The team developed two approaches to control the functions of plant
proteins related to the transport of hydrophobic pollutants.

These findings will lead to these new functions of pesticides being
utilized in agriculture, enabling safer crops to be produced.

These results were published online in the international scientific
journal Science of the Total Environment on June 23 and in Environmental Pollution'on July 18.

Main Points
* Crops in the Cucurbitaceae family can accumulate hydrophobic
pollutants
(such as dioxins) in their fruits from contaminated soil. Major
latex- like proteins (MLPs) (*2) play a key role in transporting
hydrophobic pollutants to their fruits.

* Approach 1: Treatment with a pesticide that suppresses the
expression of
MLP gene decreases the concentrations of hydrophobic pollutants
in the xylem sap.

* Approach 2: Treatment with a pesticide that binds to MLPs
inhibits the
binding of the proteins to hydrophobic pollutants. Thus, the
concentrations of hydrophobic pollutants in the xylem sap that
were transported via MLPs were reduced.

* It was shown that pesticides could provide a simple and low-cost
solution
to the production of safer crops.

* This study revealed, for the first time in the world, a new way that
pesticides can be used in agriculture, which is different from
current methods.

Research Background Hydrophobic pollutants include dioxins, the
insecticide dieldrin, and endocrine disruptors. These pollutants are
highly toxic, and their manufacture and use are now prohibited. However,
these substances were used in large quantities up until they were
banned, causing widespread environmental pollution that also affects agricultural land.



==========================================================================
The Cucurbitaceae family includes crops such as cucumbers and
squashes. Members of this family are different from other plant species
in that they accumulate high concentrations of hydrophobic pollutants in
their fruits. Associate Professor Inui et al. previously discovered that
major latex-like proteins (MLPs) in the Cucurbitaceae family play a key
role in this accumulation. MLPs bind to hydrophobic pollutants taken up
from the soil by the roots of the plant. The Cucurbitaceae family then accumulate hydrophobic pollutants in the leaves and fruits via the sap
in the stems. Consequently, MLPs are a major factor that causes crop contamination in the Cucurbitaceae family.

When crops are found to have accumulated hydrophobic pollutants above
the residual limit, all crops grown on the same land are unable to be
sold, resulting in great economic losses for the producer. For this
reason, much research has been conducted into ways to remove hydrophobic pollutants from agricultural soil, however a cost-effective and efficient method has yet to be found. Therefore, there is an urgent need to develop technology for the cultivation of safer crops on arable land contaminated
by hydrophobic pollutants.

Research Methodology This study focused on pesticides that have been
confirmed to be safe. The researchers tried two approaches designed to
suppress the accumulation of hydrophobic pollutants via MLPs: utilizing
a 'pesticide which suppresses MLP gene expression' and a 'MLP-binding pesticide'. They aimed to produce safer cucurbitaceous crops.

Approach 1 (published in 'Science of the Total Environment') The
application of a pesticide that suppresses MLP gene expression reduces
the concentration of MLPs in the roots and xylem sap (*3). This suggested
that the concentrations of hydrophobic pollutants accumulated in the
fruits via MLP would also be reduced.



========================================================================== First, experiments were carried out to select a pesticide that could
suppress MLP gene expression from five types of pesticide used on
the Cucurbitaceae family (the insecticides Guardbait, Starkle, and
Diazinon and the fungicides Benlate and Daconil). Daconil was chosen
because treatment showed that its active ingredient (*4) could reduce
MLP gene expression. Next, it was confirmed that concentrations of MLPs
in the roots and xylem sap of zucchini grown in soil contaminated with hydrophobic pollutants were reduced by the Daconil treatment. Furthermore,
the concentrations of hydrophobic pollutants in the xylem sap decreased
by 52%.

Approach 2 (published in 'Environmental Pollution') The application
of MLP-binding pesticide inhibits the binding of MLPs to hydrophobic
pollutants in the roots. In other words, the amount of MLPs that binds
to the pollutants is reduced. It was hypothesized that this approach
would decrease the concentrations of hydrophobic pollutants accumulated
in the fruits via MLPs.

First of all, chemical arrays (*5) with approximately 22,000 compounds
from the RIKEN NPDepo (*6) were used to identify compounds that bound
to MLPs. The insecticide Colt that can be applied to crops in the
Cucurbitaceae family was selected from commercial pesticides with similar structures to MLP-binding compounds. When Colt's active ingredient was
reacted with both MLPs and the hydrophobic pollutants, the concentration
of MLPs bound to these pollutants decreased by 78%. In addition, the concentrations of these pollutants in the xylem sap fell by 15% after
Colt treatment.

Further Research This study revealed, for the first time in the world,
that it is possible to cultivate safer crops in contaminated soil through
the control of the plant's functions. This achievement could reduce the
number of cases where producers experience economic losses due to being
unable to sell crops grown in contaminated soil. Furthermore, this will
also provide consumers with safe produce.

A new method of utilizing pesticides has been revealed by this
research. For the first time in the world, this study has revealed a
novel aspect of pesticides beyond their original functions of preventing
pests or weed growth.

Pesticides are thought to be extremely safe because they have to pass
numerous strict safety tests. Furthermore, the standardized treatment
of crops with pesticides is simple and inexpensive. Therefore, it is anticipated that the method developed by this study to reduce hydrophobic pollutants using pesticides will become widespread across the globe.

Glossary 1. Hydrophobic pollutants: Hydrophobic pollutants are chemical substances that do not decompose easily in the environment and accumulate easily within organisms. They are highly toxic and have been shown
to be carcinogenic and neurotoxic in humans. Hydrophobic pollutants
include dioxins, polychlorinated biphenyls, and dieldrin. Their use and manufacture have been banned in 181 countries.

2.Major latex-like protein (MLP): This protein is found in many species
of plants, including Arabidopsis thaliana, grape and apple. Particularly
in the Cucurbitaceae family, MLPs bind to hydrophobic pollutants,
transporting them to the leaves and fruits, where these pollutants then accumulate. The original functions of these proteins have yet to be
fully clarified.

3.Xylem sap: Xylem sap is a fluid found in the xylem, which is part of
the vascular bundle along with phloem. It transports water and nutrients absorbed from the roots to the leaves and fruits.

4. Active ingredient: The chemical in a commercial pesticide that performs
the product's main function (eg. insecticide or fungicide). Pesticides
also contain ingredients other than their active ingredient, such as
spreading agents, which ensure that the active ingredient adheres to
the plants or the pests. This study confirmed that active ingredients
in pesticides could control MLP functions.

5.Chemical array: An organic chemical compound is immobilized on a
chip, enabling a highly efficient evaluation of the compound's physical interactions with proteins of interest. It is difficult to immobilize
varied types and complex structures of organic compounds, compared to immobilizing single-structured DNA for DNA arrays. RIKEN's Chemical
Biology Research Group has developed an immobilization method using
a carbene with non-specific avidity (divalent carbon that only has
6 valence electrons and no charge) that will bind with the compound
regardless of its functional group.

6. RIKEN NPDepo (Natural Product Depository): A chemical compound library
being developed by the Chemical Resource Development Research Unit of
RIKEN's Chemical Biology Research Group. In addition to collecting and
storing natural compounds isolated from sources such as actinobacteria,
they are also accepting deposits from researchers in order to build up
a library of diverse chemical compounds.

This research was supported by funding from the Japan Crop Protection Association and a Sasakawa Scientific Research Grant (No. 2019-5004).


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


========================================================================== Journal Reference:
1. Kentaro Fujita, Yuki Haga, Ryouhei Yoshihara, Chisato Matsumura,
Hideyuki
Inui. Suppression of the genes responsible for transporting
hydrophobic pollutants leads to the production of safer
crops. Science of The Total Environment, 2020; 741: 140439 DOI:
10.1016/j.scitotenv.2020.140439 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200728113610.htm

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