Salicylic Acid-Mediated Abiotic Stress Tolerance - Salicylic Acid: Plant Growth and Development - page 219

Fig. 3 Complexity of
salicylic acid signalling at the
protein kinases level. For
details, see text. Numbers
indicate references:
1. Horváth et al. 2007 ;
2. Smirnoff 1993 ; 3. Torres
2010 ; 4. Li et al. 2008 ;
5. Vlot et al. 2009 ; 6. Ermak
and Davies 2001 ; 7.Chung
et al. 2004 ; 8. Pitzschke et al.
2009 ; 9. Ichimura et al. 2000 ;
10. Miles et al. 2002 ;
11. Miles et al. 2004 ;
12. Samuel et al. 2005 ;
13. Samuel and Ellis 2002 ;
14. Reyna and Yang 2006 .
calmodulin-binding protein, were also shown to be rapidly and differentially
induced by environmental signals such as temperature extremes, UV-B, salt and
wounding, by hormones such as ethylene and ABA, and by signal molecules such
as methyl JA, H 2 O 2 and SA (Yang and Poovaiah 2002 ). Calcium-dependent
protein kinases (CDPKs) sense the Ca 2+ concentration changes in plant cells and
play important roles in signalling pathways for disease resistance and various
stress responses as indicated by emerging evidences (Li et al. 2008 ).The Capsicum
annuum CaCDPK3 was rapidly induced in response to various osmotic stress
factors, and CaCDPK3 RNA expression was also induced by an incompatible
pathogen and by plant defence-related chemicals such as ethephon, SA and JA. It
is assumed that CaCDPK3 is implicated in biotic and abiotic stresses in pepper
plants (Chung et al. 2004 ). A cDNA clone (LeCRK1), encoding a novel isoform of
calcium-dependent protein kinase (CDPK), was isolated by screening a tomato
cDNA library (Leclercq et al. 2005 ). LeCRK1 transcript levels are low in
unstressed leaves, but increase in response to wounding and cold treatment. Gene
expression was slightly induced by ethylene, by spraying the leaves with a 4 mM
solution of SA, and by mechanical wounding or cold treatment. The CDPK-
mediated inhibition of SIPK and WIPK activation takes place via through ethyl-
ene. Negative communication between these distinct pathways may enable the
plant to attenuate and switch off responses once the original triggering stimulus has
been removed (Ludwig et al. 2005 ).
In Fig. 3 the complexity of salicylic acid signalling at the level of protein
kinases was demonstrated.