Salicylic Acid and Phospholipid Signaling - Salicylic Acid: Plant Growth and Development - page 36

Staxen et al. 1999 ), have established the role of PLC in the cellular response. The
identification of the in vivo activity of PLD in various cellular responses can be
evaluated by the ability of this enzyme to use primary alcohols, such as n-butanol,
instead of water in a reaction known as transphosphatidylation (Chen et al. 2011 ). In
this reaction, PLD transfers the phosphatidyl group to primary alcohols, resulting in
the formation of phosphatidylbutanol (Pbut). This lipid is not normally present in
cells, but is easy to synthesize in vivo when the cells are preincubated with low
concentrations (0.1-0.5 %) of 1-butanol (Munnik et al. 1998 ; Chen et al. 2011 ). The
involvement of PLD in various plant cellular processes has been evaluated using a
strategy similar to the one conducted by Krinke et al. ( 2009 ). The SA signaling
pathway was evaluated through the activation of PLD by Pbut formation in cell
suspensions of A. thaliana. The SA activation of PLD was dose-dependent, but none
of the existing PLD isoenzymes in the plant were significantly induced by SA. These
results suggest that the PLD isoenzyme involved in the SA response can be activated
at the protein level by an increase in translation or by the activation of existing
protein.
Liu et al. ( 2006 ) conducted a study of the relationship of SA and PIP 2 -PLC in
response to heat stress in Pisum sativum. The results obtained in this study indicate
that SA levels were significantly increased at the start of acclimation to heat stress
and that there was also an increase in PLC activity and protein level, which can be
explained due to post-translational modification. Furthermore, in experiments of
PLC inhibition by neomycin, a detectable loss of heat acclimation-induced ther-
motolerance was observed. All of this research indicates that there is a relationship
between SA and the enzymes of phospholipid signaling system, which may be a
plant pathway response.
As mentioned previously, various studies have yielded evidence of the possible
interaction between the phytoregulators and the enzymes involved in phospholipid
signaling in various plant models. However, little is known about the effect of SA
on the activity of these enzymes in vitro cultures and cell suspensions. Our
research group is interested in the signal transduction pathway that is mediated by
phospholipids and SA in cell suspensions of Capsicum chinense, which is a model
that has been used to evaluate the effect of SA in secondary metabolism.
In a preview study in 2006, Canché-Chay evaluated the in vitro enzymatic
activity of PLC in two days of a culture cycle (6 and 14) in cell suspensions of C.
chinense treated with SA (250 lM). The results indicated that the PLC activity
was stimulated by SA at 72 and 48 h after adding the plant regulator to the cell
suspensions on both days of the culture cycle. Altúzar-Molina ( 2008 ) investigated
the effect of SA on the in vitro enzymatic activities of PLC and PLD in cell
suspensions of C. chinense treated with 200 lM of SA. The results indicate that
SA inhibits the activity of both phospholipases 30 min after treatment; whereas,
the cells treated with different concentrations of SA had a variable response that
depended on the concentration. These results suggest that SA affects the phos-
pholipid signaling in cell suspensions of C. chinense, providing evidence that
implicates this signaling pathway in response to SA (Altúzar-Molina 2008 ). The
results obtained in the work described above indicates that there is most likely a