Agriculture Reference
In-Depth Information
by the expression of a class of cold-induced “cold-regulated genes”
(COR), which encode hydrophilic polypeptides and stabilize membranes
against freeze-induced injury (Artus et al., 1996). The exact role in cold
acclimation of these COR genes remain unknown, and several of them are
also induced by drought and ABA, as well as by low temperature stress.
13.5.8.1
CONVENTIONAL APPROACHES
Sources of resistance for cold tolerance are well documented in some of
the flower crops. For instance in roses
Rosa * odorata
ahardy species is
used for budding or grafting other roses (Hartmann and Kester, 1972).
Similarly
Rosa macrantha
has been used for breeding hardy cultivars.
Similarly in case of florist chrysanthemum,
Chrysanthemum bubellum
is exceptionally sturdy and used by breeders for its hardiness earlier. In
lilium,
Lilium hansonii
is extremely winter hardy and thrives well even
in lightly shaded location. Another important species,
Lilium martagon
is
winter hardy with wide adaptability for soil.
13.5.8.2
BIOTECH APPROACHES
C-binding factors (CBF), proteins with a conserved 60 amino acid AP2
domain, bind to C-repeat/DRE (drought responsive) elements in the pro-
moter region of different stress response genes such as responsive to desic-
cation 29a (
RD29a
) and are crucial for the activation of
COR
genes. The
over expression of these activators (e.g., CBF1) induces
COR
gene activ-
ity and can enhance also the freezing tolerance on nonacclimated plants
(Jaglo-Ottesen et al., 1998). The isolation of highly freeze tolerant mu-
tant
eskimo1
(
esk1
) in
Arabidopsis
, revealed another way how plants can
cope with freezing stress:
esk1
accumulates high levels of a compatible
osmolyte, proline, yet does not depend on increased expression of several
(COR) (Xin and Browse, 1998).
Protective anti freeze proteins (AFP) accumulate after cold and drought
treatment, presumably by ethylene induction (Griffith et al., 2005; Yu et
al., 2001; Yu and Griffith, 2001). These AFPs show similarities to patho-
genesis-related (PR) proteins (Hon et al., 1995) and might confer addition-
al resistance against cold tolerant pathogens. Finally, SA accumulates in
cold-stressed plants and is apparently involved in low-temperature growth
