Geoscience Reference
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accumulation of ROS and, in turn, enhanced adaptation to
drought, freezing and salt in tobacco. JERF3 induced the gene
expression of
NtCA (carbonic anhydrase), NtSOD (encodes
SOD), NtAPX1 (ascorbate peroxidase), NtAPX2 (chloroplas-
tic ascorbate peroxidase), NtGPX (glutathione peroxidase),
NtSAM1
(
S
-adenosyl-l-Met synthetase),
TOBLTP
(lipid trans-
fer protein),
NtERD10C
(early response to dehydration 10 C)
,
and
NtSPS
(
Suc-P synthase)
in responding to osmotic stress in
tobacco (Wu et al., 2008).
Jasmonic acids
The signalling molecules of JA are important for many aspects
of gene expression in plant growth, development and defence.
The importance of JA for wound signalling and its role in
the defence against insect attack was discovered in solana-
ceous plants. In
Arabidopsis
, several mutants were identified
either with compromised JA biosynthetic capacity (
fad3-2,
fad7, fad8, dad1, opr3, dde1 or dde2
) or with defects specifi-
cally in JA perception or signal transduction (
jar1, coi1 and
jin1
). The mutant plants were severely compromised in their
defence against insect attack and succumbed to infection by
pathogenic soil fungi. Huffaker et al. (2006) show that in jas-
monate-deficient
fad3, 7,8
triple-mutant plants, the
PROPEP1
and
PDF1.2
expressing are down-regulated.
A thaliana
plants
overexpressing PROPEP1 show altered root development and
enhanced resistance to the root pathogen
Pythium irregulare
(Huffaker et al., 2006). Walia et al. (2007) show that 44 genes
are up-regulated during JA treatment and salinity stress given
to Hordeum vulgare. These include photosynthesis and stress
response-related genes such as the small subunit of ribulose-1,5-
bisphosphate carboxylase, arginine decarboxylase 2 (ADC2),
carbonic anhydrase (CA), glutathionone S-transferase, fasci-
clin-like arabinogalactan (FLA10), jacalin lectin protein and a
water stress-induced tonoplast intrinsic protein. JA-responsive
Arabidopsis
genes related to salinity stress tolerance include
a salt-tolerance zinc-finger protein (STZ/ZAT10), a sodium/
potassium/calcium exchanger (At5g17860), an outward-recti-
fying potassium channel (At4g18160) and a mechano-sensitive
ion channel protein (At5g19520) (Walia et al., 2007). Like eth-
ylene, JA signal pathways are also requisite for defence against
UV-B damage. In
jar1
(insensitive to JA) mutant plants, the
UV-B-induced up-regulation of
PDF1·2
and
PR-1
gene expres-
sion level was considerably reduced compared with wild-type
plants, indicating a role of JA in the up-regulation of these
genes in response to UV-B exposure (Mackerness, 1999).
Plasma membrane intrinsic protein 1 gene, which plays an
