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

• Published in: Planta 2008-02, Vol.227 (3), p.681-695
• Main Authors: del Rosario Abraham-Juárez, Ma, del Carmen Rocha-Granados, Ma, López, Mercedes G, Rivera-Bustamante, Rafael Francisco, Ochoa-Alejo, Neftalí
• Format: Article
• Language: English
• Subjects: 3-Oxoacyl-(Acyl-Carrier-Protein) Synthase - genetics; 3-Oxoacyl-(Acyl-Carrier-Protein) Synthase - metabolism; Agriculture; Agronomy. Soil science and plant productions; Biochemical analysis; Biological and medical sciences; Biomedical and Life Sciences; Biosynthesis; Capsaicin - metabolism; Capsicum - physiology; Capsicum - virology; Chili peppers; Complementary DNA; DNA; Ecology; Economic plant physiology; Fatty acids; Forestry; Fructification, ripening. Postharvest physiology; Fruit - metabolism; Fruits; Fundamental and applied biological sciences. Psychology; Geminiviridae; Gene Silencing; Genes; Genetic Vectors; Growth and development; Life Sciences; Methyltransferases - genetics; Methyltransferases - metabolism; Original Article; Placenta; Plant Sciences; Plants; Transaminases - genetics; Transaminases - metabolism; Vegetables; Viruses
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-007-0651-7

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.