The Flavonoid Biosynthetic Enzyme Chalcone Isomerase Modulates Terpenoid Production in Glandular Trichomes of Tomato      

Abstract

Flavonoids and terpenoids are derived from distinct metabolic pathways but nevertheless serve complementary roles in mediating plant interactions with the environment. Here, we show that glandular trichomes of the anthocyanin free (af) mutant of cultivated tomato (Solanum lycopersicum) fail to accumulate both flavonoids and terpenoids. This pleiotropic metabolic deficiency was associated with loss of resistance to native populations of coleopteran herbivores under field conditions. We demonstrate that Af encodes an isoform (SlCHI1) of the flavonoid biosynthetic enzyme chalcone isomerase (CHI), which catalyzes the conversion of naringenin chalcone to naringenin and is strictly required for flavonoid production in multiple tissues of tomato. Expression of the wild-type SlCHI1 gene from its native promoter complemented the anthocyanin deficiency in af. Unexpectedly, the SlCHI1 transgene also complemented the defect in terpenoid production in glandular trichomes. Our results establish a key role for SlCHI1 in flavonoid production in tomato and reveal a link between CHI1 and terpenoid production.

Plant Glandular Trichomes: Natural Cell Factories of High Biotechnological Interest

“…Mutations of some enzymes involved in secondary metabolism also impact trichome density and/or the metabolic activity of glandular trichomes. For example, in the anthocyaninfree mutant, loss of function of the chalcone isomerase (SlCHI1) triggers a reduction of type VI trichome density and metabolic output (Kang et al, 2014), while down-regulation of DXS2, a methylerythritol 4-phosphate (MEP) enzyme, increases their density (Paetzold et al, 2010). The molecular mechanisms through which these genes affect trichome density are currently unknown.…”

Analysis of Natural and Induced Variation in Tomato Glandular Trichome Flavonoids Identifies a Gene Not Present in the Reference Genome

“…Many of these chemical compounds protect plants from herbivorous insects (Kang et al, 2010a(Kang et al, , 2010b(Kang et al, , 2014Weinhold and Baldwin, 2011). Furthermore, some trichome metabolites contribute to food flavor and aroma, for example, in mint (Mentha spp), basil (Ocimum basilicum), and hops (Humulus lupulus; Gang, 2005;Wang et al, 2008), or are used as therapeutic drugs including cannabinoids and artemisinin (Furr and Mahlberg, 1980;Klein, 2005;Liu et al, 2011).…”

The anthocyanin reduced Tomato Mutant Demonstrates the Role of Flavonols in Tomato Lateral Root and Root Hair Development

“…Aberrant accumulation of flavonoids has also been linked to hyponastic cotyledons, altered shape of pavement cells, and deformed trichomes in Arabidopsis (Kuhn et al, 2011). In tomato, a defect in a CHALCONE ISOMERASE (CHI) gene led to altered flavonoid and terpenoid accumulation in trichomes that resulted in a reduction in insect deterrence (Kang et al, 2014). In tomato and maize (Zea mays), fertilization and seed development are blocked in CHS RNA interference lines and mutants with reduced flavonoid synthesis, respectively (Mo et al, 1992;Schijlen et al, 2007).…”