Transcriptomic and Reverse Genetic Analyses of Branched-Chain Fatty Acid and Acyl Sugar Production in Solanum pennellii and Nicotiana benthamiana

TY - JOUR

T1 - Transcriptomic and Reverse Genetic Analyses of Branched-Chain Fatty Acid and Acyl Sugar Production in Solanum pennellii and Nicotiana benthamiana

AU - Slocombe, Stephen P.

AU - Schauvinhold, Ines

AU - McQuinn, Ryan P.

AU - Besser, Katrin

AU - Welsby, Nicholas A.

AU - Harper, Andrea Louise

AU - Aziz, Naveed

AU - Li, Yi

AU - Larson, Tony R.

AU - Giovannoni, James

AU - Dixon, Richard A.

AU - Broun, Pierre

PY - 2008/12

Y1 - 2008/12

N2 - Acyl sugars containing branched-chain fatty acids (BCFAs) are exuded by glandular trichomes of many species in Solanaceae, having an important defensive role against insects. From isotope-feeding studies, two modes of BCFA elongation have been proposed: (1) fatty acid synthase-mediated two-carbon elongation in the high acyl sugar-producing tomato species Solanum pennellii and Datura metel; and (2) alpha-keto acid elongation-mediated one-carbon increments in several tobacco (Nicotiana) species and a Petunia species. To investigate the molecular mechanisms underlying BCFAs and acyl sugar production in trichomes, we have taken a comparative genomic approach to identify critical enzymatic steps followed by gene silencing and metabolite analysis in S. pennellii and Nicotiana benthamiana. Our study verified the existence of distinct mechanisms of acyl sugar synthesis in Solanaceae. From microarray analyses, genes associated with a-keto acid elongation were found to be among the most strongly expressed in N. benthamiana trichomes only, supporting this model in tobacco species. Genes encoding components of the branched-chain keto-acid dehydrogenase complex were expressed at particularly high levels in trichomes of both species, and we show using virus-induced gene silencing that they are required for BCFA production in both cases and for acyl sugar synthesis in N. benthamiana. Functional analysis by down-regulation of specific KAS I genes and cerulenin inhibition indicated the involvement of the fatty acid synthase complex in BCFA production in S. pennellii. In summary, our study highlights both conserved and divergent mechanisms in the production of important defense compounds in Solanaceae and defines potential targets for engineering acyl sugar production in plants for improved pest tolerance.

AB - Acyl sugars containing branched-chain fatty acids (BCFAs) are exuded by glandular trichomes of many species in Solanaceae, having an important defensive role against insects. From isotope-feeding studies, two modes of BCFA elongation have been proposed: (1) fatty acid synthase-mediated two-carbon elongation in the high acyl sugar-producing tomato species Solanum pennellii and Datura metel; and (2) alpha-keto acid elongation-mediated one-carbon increments in several tobacco (Nicotiana) species and a Petunia species. To investigate the molecular mechanisms underlying BCFAs and acyl sugar production in trichomes, we have taken a comparative genomic approach to identify critical enzymatic steps followed by gene silencing and metabolite analysis in S. pennellii and Nicotiana benthamiana. Our study verified the existence of distinct mechanisms of acyl sugar synthesis in Solanaceae. From microarray analyses, genes associated with a-keto acid elongation were found to be among the most strongly expressed in N. benthamiana trichomes only, supporting this model in tobacco species. Genes encoding components of the branched-chain keto-acid dehydrogenase complex were expressed at particularly high levels in trichomes of both species, and we show using virus-induced gene silencing that they are required for BCFA production in both cases and for acyl sugar synthesis in N. benthamiana. Functional analysis by down-regulation of specific KAS I genes and cerulenin inhibition indicated the involvement of the fatty acid synthase complex in BCFA production in S. pennellii. In summary, our study highlights both conserved and divergent mechanisms in the production of important defense compounds in Solanaceae and defines potential targets for engineering acyl sugar production in plants for improved pest tolerance.

KW - EXPRESSED SEQUENCE TAGS

KW - SUCROSE ESTERS

KW - LYCOPERSICON-PENNELLII

KW - GLANDULAR TRICHOMES

KW - ISOPROPYLMALATE SYNTHASE

KW - APHID RESISTANCE

KW - CUTICULAR WAXES

KW - MICROARRAY DATA

KW - GLUCOSE ESTERS

KW - SURFACE-LIPIDS

UR - http://www.scopus.com/inward/record.url?scp=57749118726&partnerID=8YFLogxK

U2 - 10.1104/pp.108.129510

DO - 10.1104/pp.108.129510

M3 - Article

SN - 0032-0889

VL - 148

SP - 1830

EP - 1846

JO - Plant Physiology

JF - Plant Physiology

IS - 4

ER -