A Feedback-Insensitive Isopropylmalate Synthase Affects Acylsugar Composition in Cultivated and Wild Tomato

• Published in: Plant physiology (Bethesda) Vol. 169; no. 3; pp. 1821 - 1835
• Main Authors: Ning, Jing, Moghe, Gaurav D., Leong, Bryan, Kim, Jeongwoon, Ofner, Itai, Wang, Zhenzhen, Adams, Christopher, Jones, A. Daniel, Zamir, Dani, Last, Robert L.
• Format: Journal Article
• Language: English
• Published: United States American Society of Plant Biologists 01.11.2015
• Subjects: 2-Isopropylmalate Synthase - metabolism; Acylation; Alleles; Amino acids; Base Sequence; Biology; Biosynthesis; Carbohydrates - chemistry; Chromatography, Liquid; Enzymes; Fatty Acids - chemistry; FOCUS ON METABOLISM; Genes; Integrated pest management; Kinetics; Lycopersicon esculentum - chemistry; Lycopersicon esculentum - enzymology; Lycopersicon esculentum - genetics; Mass Spectrometry; Molecular Sequence Data; Phylogeny; Plant Proteins - genetics; Plant Proteins - metabolism; Plants; Proteins; Sequence Analysis, DNA; Solanum - chemistry; Solanum - enzymology; Solanum - genetics; Sucrose - chemistry; Trichomes; Trichomes - enzymology; Trichomes - genetics
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.15.00474

Acylsugars are insecticidal specialized metabolites produced in the glandular trichomes of plants in the Solanaceae family. In the tomato clade of theSolanumgenus, acylsugars consist of aliphatic acids of different chain lengths esterified to sucrose, or less frequently to glucose. Through liquid chromatography-mass spectrometry screening of introgression lines, we previously identified a region of chromosome 8 in theSolanum pennelliiLA0716 genome (IL8-1/8-1-1) that causes the cultivated tomatoSolanum lycopersicumto shift from producing acylsucroses with abundant 3-methylbutanoic acid acyl chains derived from leucine metabolism to 2-methylpropanoic acid acyl chains derived from valine metabolism. We describe multiple lines of evidence implicating a trichome-expressed gene from this region as playing a role in this shift.S. lycopersicumM82SlIPMS3(Solyc08g014230) encodes a functional end product inhibition-insensitive version of the committing enzyme of leucine biosynthesis, isopropylmalate synthase, missing the carboxyl-terminal 160 amino acids. In contrast, theS. pennelliiLA0716IPMS3allele found in IL8-1/8-1-1 encodes a nonfunctional truncated IPMS protein. M82 transformed with anSlIPMS3RNA interference construct exhibited an acylsugar profile similar to that of IL8-1-1, whereas the expression ofSlIPMS3in IL8-1-1 partially restored the M82 acylsugar phenotype. TheseIPMS3alleles are polymorphic in 14S. pennelliiaccessions spread throughout the geographical range of occurrence for this species and are associated with acylsugars containing varying amounts of 2-methylpropanoic acid and 3-methylbutanoic acid acyl chains.