TY - JOUR
T1 - α-Linolenic acid concentration and not wounding per se is the keyregulator of octadecanoid (oxylipin) pathway activity in rice (Oryza sativa L.) leaves
AU - Christeller, John T.
AU - Galis, Ivan
PY - 2014/10
Y1 - 2014/10
N2 - Using an invitro system composed of crushed leaf tissues to simulate the wounding response in rice leaves, we established that synthesis of jasmonic acid (JA) and jasmonic acid-isoleucine (JA-Ile) can only occur in unwounded tissue and, in wounded tissue, that only the chloroplast-located section of the octadecanoid pathway is active, resulting in the accumulation of 12-oxo-phytodienoic acid (OPDA). We further showed that OPDA accumulation invitro was inhibited by 90% using the general lipase inhibitor, tetrahydrolipstatin, indicating that production of α-linolenic acid was the rate-limiting step in octadecanoid pathway activity in rice following wounding and the enzyme capacity for an active pathway was already present. We confirmed this result by showing that added α-linolenic acid stimulated OPDA synthesis invitro and stimulated OPDA, JA and JA-Ile synthesis invivo in unwounded tissue. Thus, the response to wounding can be mimicked by the provision of free α-linolenic acid. Our results draw attention to the key importance of lipase activity in initiation of JA and JA-Ile biosynthesis and our lack of knowledge of the cognate lipase(s), lipase substrate identity and mechanism(s) of activation in wounded and unwounded tissue.
AB - Using an invitro system composed of crushed leaf tissues to simulate the wounding response in rice leaves, we established that synthesis of jasmonic acid (JA) and jasmonic acid-isoleucine (JA-Ile) can only occur in unwounded tissue and, in wounded tissue, that only the chloroplast-located section of the octadecanoid pathway is active, resulting in the accumulation of 12-oxo-phytodienoic acid (OPDA). We further showed that OPDA accumulation invitro was inhibited by 90% using the general lipase inhibitor, tetrahydrolipstatin, indicating that production of α-linolenic acid was the rate-limiting step in octadecanoid pathway activity in rice following wounding and the enzyme capacity for an active pathway was already present. We confirmed this result by showing that added α-linolenic acid stimulated OPDA synthesis invitro and stimulated OPDA, JA and JA-Ile synthesis invivo in unwounded tissue. Thus, the response to wounding can be mimicked by the provision of free α-linolenic acid. Our results draw attention to the key importance of lipase activity in initiation of JA and JA-Ile biosynthesis and our lack of knowledge of the cognate lipase(s), lipase substrate identity and mechanism(s) of activation in wounded and unwounded tissue.
KW - 12-oxo-phytodienoic acid
KW - Jasmonic acid
KW - Octadecanoid pathway
KW - Oryza sativa
KW - α-Linolenic acid
UR - http://www.scopus.com/inward/record.url?scp=84907371778&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84907371778&partnerID=8YFLogxK
U2 - 10.1016/j.plaphy.2014.07.013
DO - 10.1016/j.plaphy.2014.07.013
M3 - Article
C2 - 25129550
AN - SCOPUS:84907371778
VL - 83
SP - 117
EP - 125
JO - Plant Physiology and Biochemistry
JF - Plant Physiology and Biochemistry
SN - 0981-9428
ER -