Chemistry Reference
In-Depth Information
serine/threonine protein kinase with an SNF1/AMPK-like catalytic domain and a unique
regulatory domain (Liu et al., 2000). Individual SCaBP/CBL interacts with PKS/CIPK with
different specificities (Gong et al., 2004; Luan et al., 2002). And it is indicatied that the
interaction between SCaBP5 and PKS3 may interpret Ca
2+
signatures resulting from ABA or
drought stress signals. On the other hand, SOS3 interact with and activate the SOS2, whose
mutation also confers salt sensitivity. Then the activated SOS2 phosphorylates and regulates
ion transporters such as the Na
+
/H
+
antiporter SOS1 controlling long-distance Na
+
transport
from the root to shoot, which eventually leads to the restoration of ion homeostasis in the
cytoplasm under salt stress (Zhu, J.K., 2003).
In light of salt stress, like other stresses, it is perceived at cell membrane and then trigger
intracellular-signaling cascade including the generation of secondary messenger molecules
like Ca
2+
and protons. For instance, it was found that in barley roots, under NaCl stress,
Ca
2+
-CaM system may work in activating tonoplast H
+
-ATPase and regulating Na
+
and K
+
uptake with involvement of SOS signal transduction pathway (Brini et al., 2007). In
Arabidopsis, experiments to overexpress AtCaMBP25 (a CaM binding protein) who may be
a a negative regulator of osmotic stress tolerance find the transgenic Arabidopsis plants
show higher sensitivity to osmotic stress, while the antisense plants gain more tolerance
under salt stress (Perruc, E. et al., 2004).
Furthermore, when it comes to uncomfortable temperature, is there any position for Ca
2+
?
For sure. The Ca
2+
channels have shown their power for the growth of root hairs and the low
temperature acclimation of chilling-resistant plants. That's why we find data indicating that
the activity and stability of Ca
2+
-ATPase under 2 °C low temperature are the key factors in
the development of cold resistance of winter wheat (Yamaguchi-Shinozaki, 2006). Moreover
the studies on Arabidopsis mutants displaying reduced tonoplast Ca
2+
/H
+
antiport (CAX1)
activity indicate that CAX1 participates in the development of the cold acclimation response
(Lecourieux et al., 2006). On the other field of temperature acclimation, there exists data
showing in Arabidopsis, Ca
2+
/CaM have gotten involved in heat shock response (Zhang et
al., 2009). And we also find some researches on overexpression of a CDPK in rice which
brings increased tolerance to cold and salt stress (Saijo, Y. et al., 2000).
Taken together, depending on the type of signal or the type of cell, internal and/or external
Ca
2+
stores could be involved in raising [Ca
2+
]
cyt
(Dodd et al., 2010; Kudla et al., 2010). Both
types of Ca
2+
transporters, namely, Ca
2+
-ATPases and CAXs involve in plant responses by
regulating [Ca
2+
]
cyt
. Based on that, regulating cellular and intercellular Ca
2+
signaling
networks brings improving resistances or tolerances. And seeing from the regulation
networks of stress responses to drought, salt and cold stress, we find Ca
2+
and its interacting
proteins may be the cross-talks among ABA-dependent, MAPK and other stress signaling
pathways. Anyway, we can see the core of Ca
2+
actions in relaying abiotic stress signaling
depends on how to translate Ca
2+
signatures to specific protein phosphorylation
cascades,which we have mentioned above, so in the following part, we are going to trace the
performance of phosphoproteins in signal transduction.
