Akademik Veri Yönetim Sistemi
Atıcı Ö. (Yürütücü), Aksakal Ö.
TÜBİTAK Projesi, 2018 - 2020
Methylglyoxal
(MG), a high-level
reactive carbonyl compound and a powerful oxidant is a mutagenic and cytotoxic
intermediate that can induce DNA breakdown and point mutations, but at the same
time causing Advanced Glycation End Products (AGE’s). MG is also known to
disrupt glucose metabolism, which leads to intracellular ATP depletion and
mitochondrial dysfunctions Kaur et al. 2014). MG in the cells is produced
during enzymatic and non-enzymatic elimination of inorganic phosphate (Pi),
especially under stressful conditions, from glycolytic intermediates including
dihydroxyacetone phosphate and glyceraldehyde-3-phosphate. Other sources of
intracellular MG include catabolism of carbohydrate, lipid, and nitrogenous
compounds (such as proteins). Almost all live systems, including plants, have
glyoxalase systems in cells to counteract the increased MG toxicity under stressful
conditions. The glyoxalase system is mainly composed of two enzymes, Glyoxalase-I
(Gly-I) and Glyoxalase-II (Gly-II). Gly-I converts MG to S-lactoylglutathion
(SLG) by using reduced glutathione (GSH). The S-lactoylglutathione formed here
is converted by GLY-II into D-lactate and GSH (Hossain et al., 2009; Kaur et al., 2014). Thus,
MG is scavenging in the cells.
Although MG toxicity, which was discovered about
eighty years ago, has been studied extensively in animal organisms, very few
studies have been conducted on plants. For this reason, biochemical and
physiological responses to both exogenous and endogenous MG accumulation in
plants are still very unclear. It is believed that the primary role of this
system is the detoxification of the MG toxin. However, the identification of isoforms
of the enzymes in the system that are catalytic to other substrates from known
substrates (MG and SLG) suggests that the glyoxalase system can play another
additional role. The increase of glyoxalase expression in biotic and abiotic
stress response conditions, and consequently the overexpression of enzymes of
which as a resulting the increased stress tolerance of plants strengthen these
approaches. The glyoxalase system is found in almost every organism, including
plants, and the organism is expressed in all tissues. This manifests the
importance of the glyoxalase system but also shows why it is important to work
on it (Thornalley,
1990; Kalapos, 1999).
In our project, the relationship between the
glyoxalase system and nitrogen metabolism became intense. Because, nitrogen
metabolism is regulated by complex mechanisms to optimize the growth of plants,
and plays an important role during the period of germination, vegetative and
generative growth-development. In this situation, In our work, the following
were the questions that were primarily addressed: What are the direct roles of
MG on the enzymes of the glyoxalase system, which are exogenously applied to a
plant? What are the effects of exogenous MG on the enzymes of plant nitrogen
metabolism (nitrate reductase, nitrite reductase, glutamate synthase, and
glutamine synthase)? Is there a relationship between the glyoxalase system and
nitrogen metabolism in the response to MG toxicity? There is significant
disunity in the literature on these issues. In our work, to resolve these
questions, we will use tools to determine the effects
of MG administration on both gene expression levels and enzymatic activity
levels of the enzymes involved in both systems (glyoxalase and nitrogen
metabolism) in the Arabidopsis thaliana,
a model organism. The findings are expected to reveal the effects of MG on
nitrogen metabolism in plants and to explain the relationship between nitrogen
metabolism and glyoxalase systems. In addition, our findings will contribute
significantly to reducing the toxicity of MG, which increases in almost all
stress conditions and the regulation of stress response in plants.