Abstract |
Tetranychus urticae Koch, 1836 is a major agricultural pest that belongs to the Subclass of Acari.
It is known for its polyphagous behavior, as it can infest more than 1.100 different plant species, as well
as its ability to develop resistance to insecticides/acaricides in very short periods after their first
application. Some of its biological characteristics contribute to resistance development such as its high
fecundity, haplo-diploid sex determination and short life cycle. Additional characteristics such as its
polyphagous behavior have been correlated with the ability of T. urticae to counteract the effect of
insecticides based on the pre-adaptation theory. The sequencing of T.urticae genome further supports
this hypothesis since it revealed an extraordinary arsenal of detoxification enzymes, many of which are
T. urticae specific. Previous studies have shown the over-expression of members of CYP392 family
(CYP392A11, CYP392A12, CYP392A16, CYP392D2, CYP392D8, CYP392D10) in resistant strains with
CYP392A11 metabolizing the METI insecticides fenpyroximate and cyenopyrafen and CYP392A16
metabolizing the avermectin insecticide abamectin. Additionally, members of GST family (TuGSTd05,
TuGSTd10, TuGSTd14) have been found to be over-expressed in resistant strains with TuGSTd05 possibly
metabolizing the METI insecticide cyflumetofen. In this study we aimed in localizing three major enzyme
families (CYP392A, GSTd, ID-RCD). The first two are of known function and it has been confirmed that
their increased presence confers resistance. The third is a newly discovered family in arthropods and
constitutes a compelling case of horizontal gene transfer, with its function being unknown. Additionally,
there are several documented cases where the function of ID-RCDs has been correlated with digestion
or detoxification. We raised 4 different antibodies (anti-CYP392A, anti-CYP392D, anti-GSTd and anti-
Dioxygenase) each of which was first tested on Western blot analyses to see their specificity. Three out
of four were not specific for the selected subfamily/family (anti-CYP392D, anti-GSTd and anti-
Dioxygenase) so we continued the immunolocalization studies with anti-CYP392A and anti-CYP392A16,
which were used in cryo-sections and whole mount specimens of T. urticae adult females. A part of the
results using anti-CYP392A16 indicates the possible presence of A16 in nerve cells proximal to the
central nervous mass of T. urticae. This finding is in accordance with previously conducted experiments
on different organisms such as the mosquito Aedes albopictus (Grigoraki et al. 2016), the silkworm
Bombyx mori (Xuan et al. 2014) and the red floor beetle Tribolium castaneum (Zhu et al. 2010). Our
efforts should be focused in finalizing the immunolocalization protocol so that our data are consistent,
while the co-localization of CPR, the redox partner of CYP392A16, would further support the data.
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