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Virus-induced silencing of Comt, pAmt and Kas genes results in a reduction of capsaicinoid accumulation in chili pepper fruits

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Capsaicinoids are responsible for the pungent taste of chili pepper fruits of Capsicum species. Capsaicinoids are biosynthesized through both the phenylpropanoid and the branched-fatty acids pathways. Fragments of Comt (encoding a caffeic acid O-methyltransferase), pAmt (a putative aminotransferase), and Kas (a β-keto-acyl-[acyl-carrier-protein] synthase) genes, that are differentially expressed in placenta tissue of pungent chili pepper, were individually inserted into a Pepper huasteco yellow veins virus (PHYVV)-derived vector to determine, by virus-induced gene silencing, irrespective of whether these genes are involved in the biosynthesis of capsaicinoids. Reduction of the respective mRNA levels as well as the presence of related siRNAs confirmed the silencing of these three genes. Morphological alterations were evident in plants inoculated with PHYVV::Comt and PHYVV::Kas constructs; however, plants inoculated with PHYVV::pAmt showed no evident alterations. On the other hand, fruit setting was normal in all cases. Biochemical analysis of placenta tissues showed that, indeed, independent silencing of all three genes led to a dramatic reduction in capsaicinoid content in the fruits demonstrating the participation of these genes in capsaicinoid biosynthesis. Using this approach it was possible to generate non-pungent chili peppers at high efficiency.

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Acl1 :

Acyl carrier protein gene


Acyl-CoA synthase

AT3 :

Putative acyltransferase gene


BEAT, AHCTs, HCBT and DAT superfamily


Branched-chain amino acid transferase


Bovine serum albumin


4-Coumarate-CoA ligase

Comt :

Caffeic acid O-methyltransferase gene

csy1 :

Capsaicin synthase gene


Coumaroyl shikimate/quinate 3-hydroxylase


Cinnamic acid 4-hydroxylase


Days post-anthesis


Days post-infection

FatA :

Acyl-ACP thioesterase gene


Fatty acid synthase complex


Hydroxycinnamoyl transferase

Kas :

β-keto-acyl-[acyl-carrier-protein] synthase gene


Phenylalanine ammonia-lyase

pAmt :

Putative aminotransferase gene


Post-transcriptional gene silencing


Pepper huasteco yellow veins virus


Small interfering RNA


Virus-induced gene silencing




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We thank Dr. Mary A. O’Connell, New Mexico State University, for kindly supplying the cDNA clones used in this work, and Dr. L. Herrera-Estrella, Cinvestav Campus Guanajuato, for the critical review of the manuscript. We are also grateful to Dr. Hector G. Núñez-Palenius, Cinvestav Campus Guanajuato, for assistance in statistical data analysis. We acknowledge CONACYT and CONCYTEG (Mexico) for the fellowship support to M.R. Abraham-Juárez.

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Correspondence to Neftalí Ochoa-Alejo.

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del Rosario Abraham-Juárez, M., del Carmen Rocha-Granados, M., López, M.G. et al. Virus-induced silencing of Comt, pAmt and Kas genes results in a reduction of capsaicinoid accumulation in chili pepper fruits. Planta 227, 681–695 (2008).

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