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Plant Physiol Biochem

Title:		Medicago truncatula (E)-beta-ocimene synthase is induced by insect herbivory with corresponding increases in emission of volatile ocimene
Author(s):		Navia-Gine WG; Yuan JS; Mauromoustakos A; Murphy JB; Chen F; Korth KL;
Address:		"Department of Plant Pathology, University of Arkansas, Fayetteville, 72701, USA"
Journal Title:		Plant Physiol Biochem
Year:		2009
Volume:		20090208
Issue:		5
Page Number:		416 - 425
DOI:		10.1016/j.plaphy.2009.01.008
ISSN/ISBN:		1873-2690 (Electronic) 0981-9428 (Linking)
Abstract:		"Virtually all plants are able to recognize attack by herbivorous insects and release volatile organic compounds (VOC) in response. Terpenes are the most abundant and varied class of insect-induced VOC from plants. Four genes encoding putative terpene synthases (MtTps1, MtTps2, MtTps3 and MtTps4) were shown to accumulate in Medicago truncatula Gaertn. in response to Spodoptera exigua (Hubner) feeding and methyl jasmonate treatment in a previous study [S.K. Gomez, M.M. Cox, J.C. Bede, K.K. Inoue, H.T. Alborn, J.H. Tumlinson, K.L. Korth, Lepidopteran herbivory and oral factors induce transcripts encoding novel terpene synthases in Medicago truncatula, Arch. Insect Biochem. Physiol. 58 (2005) 114-127.] The focus of the current study is the functional characterization of one (MtTps4) of these four genes. Using an M. truncatula cDNA clone, the insect-inducible putative terpene synthase was expressed in Escherichiacoli and shown to convert geranyl diphosphate (GPP) into the monoterpene (E)-beta-ocimene as the major product. The clone was therefore designated M. truncatula (E)-beta-ocimene synthase (MtEBOS). Transcripts encoding this enzyme accumulate in M. truncatula leaves in response to exogenous jasmonic acid treatments, lepidopteran herbivory, and lepidopteran oral secretions. Treatment with the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC) did not cause an increase in MtEBOS transcripts. The volatile (E)-beta-ocimene was released from leaves of both undamaged and insect-damaged plants, but at levels two-fold higher in insect-damaged M. truncatula. Although leaves have low constitutive levels of MtEBOS transcripts, RNA blot analysis indicates no constitutive expression in flowers, stems or roots. The strong insect-induced expression of this gene, and its correspondence with release of volatile ocimene, suggest that it plays an active role in indirect insect defenses in M. truncatula"
Keywords:		"Acyclic Monoterpenes Alkenes/*metabolism Alkyl and Aryl Transferases/classification/genetics/*metabolism Amino Acid Sequence Animals DNA, Complementary/genetics Diphosphates/metabolism Diterpenes/metabolism Escherichia coli/genetics Gas Chromatography-Mas;"
Notes:		"MedlineNavia-Gine, Wayra G Yuan, Joshua S Mauromoustakos, Andy Murphy, J Brad Chen, Feng Korth, Kenneth L eng Research Support, Non-U.S. Gov't France 2009/03/03 Plant Physiol Biochem. 2009 May; 47(5):416-25. doi: 10.1016/j.plaphy.2009.01.008. Epub 2009 Feb 8"