Agriculture Reference
In-Depth Information
Comparison of guard cell expression profiles with those of mesophyll cells
identified 64 transcripts that were expressed preferentially in guard cells. These
genes encode TFs, signal transduction proteins such as protein kinases, receptor
protein kinases and metabolic pathway proteins. Expression profiling has revealed
that ABA modulates the expression of many ABA signalling components in guard
cells at the transcript level (Leonhardt et al.
2004
). Furthermore, it is important
to identify the function of previously uncharacterised genes that responded to the
application of exogenous ABA and H
2
O
2
. However, the functions of many of these
genes and their products remain to be determined; these represent areas of future
investigation.
10.5 Concluding Remarks
The present chapter described ROS turnover under ABA treatment and stress con-
ditions, their biological roles in plant growth, development and stress responses.
ROS can induce oxidative damage and defence-responsive activities in plants, with
the dual roles of ROS depending on the balance between ROS production and the
scavenging system. In plant cells and tissues, both ABA and ROS can be induced
by drought, cold and salt stresses. Many components in ABA-regulated stress
adaptation and resistance in plants have been identified, with a complex regulatory
network involving ROS being involved in this biological process.
Some other unanswered questions are: What are the components in both ABA
and ROS signalling? Although many genes have been revealed to be involved in such
signalling, it is still difficult to draw precise conclusions on the regulatory system.
Different genetic responses are induced under different abiotic and biotic stresses,
and ROS generation is the central response to both abiotic and biotic stresses. In
terms of how ROS signal transduction modulates changes in gene expression upon
exposure to different stresses, the underlying molecular mechanisms are largely
unknown, especially for the ABA response. For example, are all of the genes regu-
lated by ROS signalling in the ABA pathway sensitive to the redox state of the cell?
Answering these questions might require combining the screening of more ROS-
response mutants with the use of advanced imaging tools (Song et al.
2014
).
Other relevant questions include: How are ABA and ROS signals transmitted a
long distance and what happens during cell-to-cell communication? Whether does
H
2
O
2
replace ABA for long-distance transportation in plant? Although, H
2
O
2
has
been believed to cross membranes freely studies have indicated that the diffusion
is limited and its transport need channel proteins such as aquaporins (Bienert et al.
2006
). Therefore, analysis of the mechanism of long-distance transmit will be a
new target in ABA and ROS research.
Acknowledgments
Research in the author's laboratories was supported by the National Key
Basic Special Funds (2012CB114301) and the National Natural Science Foundation of China
(90817106).
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