Agriculture Reference
In-Depth Information
2010
). By contrast, downregulation of invertases or an upregulation of invertase
inhibitors proved to be a very efficient strategy to prevent cold-induced sweetening
in potato tubers, in order to maintain the quality of chips and French fries, and to
avoid browning and the formation of toxic acrylamides during the baking process
(Bhaskar et al.
2010
).
Cold stress is an important threat for the crops, especially during early growth
stages and seed emergence (Zinn et al.
2010
; Ohnishi et al.
2010
). Rice, one of
the major crops, is a good example of a species that is very sensitive to chilling.
Expansion of rice cultivation into regions that experience periodic or sustained low
temperatures, such as the Hokkaido region of Japan, has increased the risk of crop
loss through chilling injury (Kawakami et al.
2008
). Under low temperature condi-
tions, rice suffers from leaf turgor losses and prolonged low temperatures result in
leaf dehydration (Kawakami et al.
2008
). It is a known fact that chilling-sensitive
plants experience increased oxidative stress at temperatures not far above 0 °C (Val-
luru and Van den Ende
2008
). Although chilling and frost tolerance are generally
considered as complex multigenic treats (Hughes and Dunn
1996
), it was rather
spectacular and unexpected to see that chilling tolerance could be achieved in rice
(Kawakami et al.
2008
) by introducing a single gene encoding a 1-SST for fructan
biosynthesis, counteracting oxidative stress (see above). However, introducing FTs
in non-fructan accumulating crops may not always be that easy. For instance, intro-
ducing fructan synthesis in
Arabidopsis
proved to be difficult, only resulting in a
minor accumulation of low DP fructans (Valluru and Van den Ende
2008
). Perhaps,
this can be explained by the high invertase and/or FEH activities in this species. It
should be highlighted again that, besides the actual presence of a particular sugar
as antioxidant and/or osmoprotectant, the exact subcellular location of such com-
pounds is even more important for their functionality (Iftime et al.
2011
).
In conclusion, the sensitivity of crops to harsh climates and soil conditions is a
major limitation for worldwide food production. Worldwide, researchers look for
new, desirable traits and their genes in extremophiles and resurrection plants, spe-
cies that can survive extreme stress conditions (Amtmann
2009
; Otto et al.
2009
).
Among many opportunities for crop improvement, the introduction of specific sug-
ars (as antioxidants/osmoprotectants) and the modulation of key enzymes in sugar
metabolism (or their inhibitors/partners) are very promising strategies to produce
stress-tolerant crops with higher yield and quality.
References
Albrecht G, Biemelt S, Baumgartner S (1997) Accumulation of fructans following oxygen
deficiency stress in related plant species with different flooding tolerances. New Phytol
136:137-144
Amiard V, Morvan-Bertrand A, Billard JP, Huault C, Keller F, Prud'homme MP (2003) Fructans,
but not the sucrosyl-galactosides, raffinose and loliose, are affected by drought stress in peren-
nial ryegrass. Plant Physiol 132:2218-2229
