Agriculture Reference
In-Depth Information
by the barrel medic
MtOGG1
and
MtFPG
genes. The expression profiles of both
genes were evaluated in barrel medic plantlets grown
in vitro
under oxidative stress
conditions induced by copper and PEG, respectively.
The
Tdp1
gene encoding tyrosyl-DNA phosphodiesterase has been extensively
investigated in animal cells, due to the role of this enzyme in the repair of topoi-
somerase I-DNA covalent lesions (Yang et al.
1996
). Macovei et al. (
2010
) reported
for the first time in plants on the
Tdp1
gene family from barrel medic, composed of
two members,
MtTdp1
α (alpha) and
MtTdp1
β (beta). The expression profiles of the
MtTdp1
genes were evaluated in plantlets grown
in vitro
using copper and PEG as
stress agents. Both
Tdp1
genes were significantly up-regulated in response to heavy
metal and osmotic stress, suggesting for a requirement of the
Tdp1
function under
stress conditions. From this point of view, the response of
MtTdp1
genes to stress
seems to be in agreement with the literature available on the animal
Tdp1
gene (Lu
et al.
2004
).
In a recent work (Lebedeva et al.
2011
), a novel role played by TDP1 has been
reported, since the enzyme contributes to the removal of abasic or AP sites, the
key BER intermediates (Barnes and Lindhal
2004
). The human TDP1 protein can
initiate repair of AP-sites within the APE (apurinic/apyrimidinic endonuclease I)-
independent BER pathway through the cleavage of the AP site and release of 3′- and
5′ phosphate termini. Due to the multiple functions played by the human TDP1
enzyme in DNA repair, it is possible that the plant
tdp1
α (alpha) and
(beta) genes
might represent effective tools for biotechnological applications aimed at improv-
ing stress tolerance in crops.
7 Environmental Stresses, DNA Repair and Seed Vigor
Despite the relevant effects of environmental stresses on crop productivity, only
limited attention has been given to DNA repair in seeds and to its involvement in
those mechanisms conferring seed protection against stress. It is generally acknowl-
edged that high crop productivity requires efficient and uniform seed germination
and increased seed vigor. The effects of adverse environmental conditions on seed
quality can be easily scored using common indicators of viability such as germina-
tion speed and percentage (Bewley and Black
1994
).
Dry seeds are tolerant to adverse environments; however germination and the
first stages of seedling establishment represent highly vulnerable steps of the plant
lifecycle (Kranner et al.
2010
). Drought, osmotic stress, salt, low temperatures, and
heavy metals adversely affect seed germination and in natural environment seeds
might frequently be challenged by detrimental combination of stresses (Lee et al.
2010
).
The stress response in germinating seeds is regulated at different levels and sig-
naling events play a crucial role. It has been suggested that ROS could be involved
in the regulation of cell signaling in dry seeds and within this context distinct roles
have been hypothesized for short- and long-lived radicals (El-Maarouf-Bouteau and
