Agriculture Reference
In-Depth Information
interesting tools to improve the plant tolerance and the work carried out on plant
DEAD-box helicases has undoubtedly contributed to expand the knowledge in this
research field (Vashisht and Tuteja
2006
). DEAD-box helicases play an essential
role in several basal processes of DNA metabolism, including DNA repair. They are
motor proteins that catalyze the ATP-dependent unwinding of duplex DNA/RNA at
the damaged area, allowing repair. DEAD-box RNA helicase-encoding genes are
up-regulated in response to salinity stress, as reported for the sorghum (
Hordeum
vulgaris
L.; Nakamura et al.
2004
). Stress-responsive helicases have been charac-
terized also in
Pisum sativum
. The
PDH45
helicase is induced in pea seedlings in
response to high salt and the overexpression of the
PDH45
gene in tobacco resulted
in salinity tolerance (Sanan-Mishra et al.
2005
). A similar response was observed
for the
PDH47
gene, induced by cold and salinity stress (Vashisht and Tuteja
2005
).
Water deficit is another major abiotic stress, affecting crop growth and reducing
sustainable food production. Besides the known general effects of drought stress
on vegetative growth, water shortage is detrimental at the reproductive stage in
most cereals and strong efforts have been made to improve drought tolerance at this
specific stage (Oh et al.
2009
). Drought tolerance relies on multiple gene functions,
some of them participating in the early response (e.g., signal transduction) and oth-
ers required during the late response. The latter includes not only genes for water
transport and osmotic balance but also antioxidant and DNA repair gene functions
(Zhu
2001
). As for the contribution of antioxidant cellular mechanisms to drought
tolerance, the key role of catalase, superoxide dismutase and peroxidase enzymes
has been demonstrated together with the involvement of novel ROS scavenger such
as metallothioneins (Seki et al.
2001
). Recent studies carried out on the model le-
gume
Medicago truncatula
(barrel medic) have highlighted the novel DNA repair
gene functions, participating in the nucleotide- and base-excision repair pathways
(NER and BER, respectively), which turned out to be significantly up-regulated in
response to water stress (Macovei et al.
2010
; Macovei et al.
2011a
,
b
). A detailed
description of these results is given in the following paragraph.
Air pollution, resulting from the release of toxic gases and other poisons to the
environment, is another abiotic stress responsible for crop yield losses (Seyydnejad
et al.
2011
). Pollutants include sulfur and nitrogen oxides, carbon monoxide, toxic
metals, organic molecules, and radioactive isotopes. As for several other environ-
mental stresses, exposure to air pollutants causes oxidative stress with the conse-
quent activation of ROS scavenging processes. This is another relevant research
field in which molecular investigations related to genotoxic effects and protection
mechanisms should be supported.
Environmental heavy metal pollution has been dramatically increasing due to
extensive mining and industrial activities. Heavy metals, e.g., copper, cadmium,
chromium, and lead, released from different anthropogenic sources severely affect
ecosystems and crop productivity, posing a risk to the food chain (Peralta-Videa
et al.
2009
). The genotoxic effects of heavy metals have been widely investigated
in animal cells (Garcia-teston et al.
2010
). In plants, several deleterious effects in-
duced by metal exposure have been attributed to oxidative stress (Benavides et al.
2005
). Intoxication with pollutant metals generates ROS which need to be removed
