A tomato enzyme synthesizes (+)-7-iso-jasmonoyl-L-isoleucine in wounded leaves.
Jasmonoyl-L-isoleucine (JA-Ile) is a key jasmonate signal that probably functions in all plant species. The JASMONATE RESISTANT 1 (JAR1) enzyme synthesizes JA-Ile in Arabidopsis [Arabidopsis thaliana (L.) Heynh.], but a similar enzyme from tomato [Solanum lycopersicum (L.)] was not previously described. Tomato SlJAR1 has 66% sequence identity with Arabidopsis JAR1 and the SlJAR1-GST fusion protein purified from Escherichia coli catalyzed the formation of JA-amino acid conjugates in vitro. Kinetic analysis showed the enzyme has a strong preference for Ile over Leu and Val and it was about 10-fold more active with (+)-7-iso-JA than with its epimer (-)-JA. Leaf wounding rapidly increased JA-Ile 50-fold to about 450 pmol g(-1) FW at 30 min after wounding, while conjugates with Leu, Phe, Val and Met were only marginally increased or not detected. Nearly all of the endogenous JA-Ile was the bioactive epimer (+)-7-iso-JA-Ile and there was no evidence for its conversion to (-)-JA-Ile up to 6 h after wounding. A transgenic RNAi approach was used to suppress SlJAR1 transcript that reduced JA-Ile accumulation by 50-75%, suggesting that other JA conjugating enzymes may be present. These results show that SlJAR1 synthesizes the bioactive conjugate (+)-7-iso-JA-Ile and this is the predominant isomer accumulated in wounded tomato leaves.
Suza
Walter P
WP
Arkansas Biosciences Institute, Arkansas State University, PO Box 639, State University, Jonesboro, AR 72467, USA.
Rowe
Martha L
ML
Hamberg
Mats
M
Staswick
Paul E
PE
D029681:Arabidopsis Proteins / Q000737:chemistry / Q000502:physiology; D003517:Cyclopentanes; D007532:Isoleucine / Q000031:analogs & derivatives* / Q000096:biosynthesis; D007700:Kinetics; D018551:Solanum lycopersicum / Q000201:enzymology* / Q000378:metabolism; D009713:Nucleotidyltransferases / Q000737:chemistry / Q000502:physiology; D018515:Plant Leaves / Q000201:enzymology / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry / Q000502:physiology*; D030821:Plants, Genetically Modified / Q000378:metabolism; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D013379:Substrate Specificity; D010453:Peptide Synthases
D029681:Arabidopsis Proteins; D003517:Cyclopentanes; D007532:Isoleucine; D009713:Nucleotidyltransferases; D010940:Plant Proteins; D012333:RNA, Messenger; C532883:jasmonoyl-isoleucine; C412831:AT2G46370 protein, Arabidopsis; D010453:Peptide Synthases