Production and use of the insecticide
chlordecone has caused long-term
environmental pollution in the James River area and the French West
Indies (FWI) that has resulted in acute human-health problems and
a social crisis. High levels of chlordecone in FWI soils, even after
its ban decades ago, and the absence of detection of transformation
products (TPs), have suggested that chlordecone is virtually nonbiodegradable
in the environment. Here, we investigated laboratory biodegradation,
consisting of bacterial liquid cultures and microcosms inoculated
with FWI soils, using a dual nontargeted GC-MS and LC-HRMS approach.
In addition to previously reported, partly characterized hydrochlordecones
and polychloroindenes (families A and B), we discovered 14 new chlordecone
TPs, assigned to four families (B, C, D, and E). Organic synthesis
and NMR analyses allowed us to achieve the complete structural elucidation
of 19 TPs. Members of TP families A, B, C, and E were detected in
soil, sediment, and water samples from Martinique and include 17 TPs
not initially found in commercial chlordecone formulations. 2,4,5,6,7-Pentachloroindene
was the most prominent TP, with levels similar to those of chlordecone.
Overall, our results clearly show that chlordecone pollution extends
beyond the parent chlordecone molecule and includes a considerable
number of previously undetected TPs. Structural diversity of the identified
TPs illustrates the complexity of chlordecone degradation in the environment
and raises the possibility of extensive worldwide pollution of soil
and aquatic ecosystems by chlordecone TPs.
Flowers are essential but vulnerable plant organs, exposed to pollinators and florivores; however, flower chemical defenses are rarely investigated. We show here that two clustered terpene synthase and cytochrome P450 encoding genes (TPS11 and CYP706A3) on chromosome 5 of Arabidopsis (Arabidopsis thaliana) are tightly coexpressed in floral tissues, upon anthesis and during floral bud development. TPS11 was previously reported to generate a blend of sesquiterpenes. By heterologous coexpression of TPS11 and CYP706A3 in yeast (Saccharomyces cerevisiae) and Nicotiana benthamiana, we demonstrate that CYP706A3 is active on TPS11 products and also further oxidizes its own primary oxidation products. Analysis of headspace and soluble metabolites in cyp706a3 and 35S:CYP706A3 mutants indicate that CYP706A3-mediated metabolism largely suppresses sesquiterpene and most monoterpene emissions from opening flowers, and generates terpene oxides that are retained in floral tissues. In flower buds, the combined expression of TPS11 and CYP706A3 also suppresses volatile emissions and generates soluble sesquiterpene oxides. Florivory assays with the Brassicaceae specialist Plutella xylostella demonstrate that insect larvae avoid feeding on buds expressing CYP706A3 and accumulating terpene oxides. Composition of the floral microbiome appears also to be modulated by CYP706A3 expression. TPS11 and CYP706A3 simultaneously evolved within Brassicaceae and form the most versatile functional gene cluster described in higher plants so far.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.