Agriculture Reference
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stimulated ROS production in adhering cells, or what the relationship is between
the cell ROS-scavenging system and newly formed ROS in each cell that partici-
pates in this long-distance signalling pathway.
The rapid production of ROS in response to different environmental conditions
and the ability of cells to scavenge ROS using their antioxidant system provide
another advantage for ROS signalling. Given that the production and scavenging
of ROS occur at the same time, these two processes produce rapid changes in ROS
levels, which respond quickly to environmental signals.
Studies that investigated ROS-mediated signalling and its association with
the expression of specific genes have identified a range of elements that respond
to oxidative stress, including specific promoters and transcription factors (TFs)
(Aslund et al.
1999
). However, the redox-sensing mechanisms and the associated
signalling pathways induced by ROS are still somewhat unclear, and the sensors
for ROS in plant cells have yet to be identified.
Pinheiro and Chaves (
2011
) undertook a literature survey on reports pub-
lished between 1995 and February 2010 that revealed strong associations between
drought, photosynthesis, ROS, ABA, sucrose and starch at the metabolite level.
Analysis of protein and gene networks also revealed important roles for sugars,
starch, ROS and ABA pathways in responses to drought and changes in photosyn-
thesis. Some regulatory proteins that are associated with photosynthetic responses
and drought are the TFs T6L1.5, HY5, AHBP-1B and GBF3, members of the bZIP
(basic leucine zipper domain) family, and a TF that belongs to the abscisic acid-
insensitive 3 (ABI3) family. The involvement of the bZIP and ABI3 TFs, both of
which are ABA-dependent, in responses to drought and changes in photosynthe-
sis has also been reviewed (Saibo et al.
2009
). Binding of ABI4 to the DNA ele-
ment CCACGT might prevent that promoter sequence from being bound by other
TF, which likely prolongs the duration of signalling. The CCAAT binding factor A
(CBFA), which is a subunit of the HAP2/HAP3/HAP5 (haeme activator protein)
trimeric transcription complex, acts downstream of ABI4. When an emergency
occurs (such as herbicide treatment or environmental stress followed by ABA and
ROS accumulation), the master transcription factor ABI4 down-regulates certain
TFs, such CBFA. Thereafter, some other TF subunits enter the transcription com-
plex, and the transcriptional efficiency of stress-responsive genes (including the
transcription co-factor CBP) is improved instantaneously (Zhang et al.
2013
).
Whereas H
2
O
2
can oxidise cysteine residues in proteins to form cysteine sul-
phenic acid or disulphide bonds, cellular reductants can reduce them back to
cysteine. Depending on these mechanisms, several putative H
2
O
2
sensors have
been revealed. These include AtGPX3, HSF and two cysteine-rich receptor-like
kinase and a leucine-rich repeat (LRR-RLK) proteins in
Arabidopsis
(Miao et al.
2006
; Miller and Mittler
2006
; Tripathy and Oelmller
2012
), and their redox
states are regulated by ROS.
Functional genomics has yet to be used to detect ROS receptors or ROS-sensing
TFs in plant extracts. It is important to identify the genes and the mechanisms of oxida-
tive stress that can support the breeding of plants that can resist environmental stress.
Studies to reveal ROS signal function in ABA-regulated stomatal closure have revealed
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