Variation of Herbivore-Induced Volatile Terpenes among Arabidopsis Ecotypes Depends on Allelic Differences and Subcellular Targeting of Two Terpene Synthases, TPS02 and TPS03    

Abstract

When attacked by insects, plants release mixtures of volatile compounds that are beneficial for direct or indirect defense. Natural variation of volatile emissions frequently occurs between and within plant species, but knowledge of the underlying molecular mechanisms is limited. We investigated intraspecific differences of volatile emissions induced from rosette leaves of 27 accessions of Arabidopsis (Arabidopsis thaliana) upon treatment with coronalon, a jasmonate mimic eliciting responses similar to those caused by insect feeding. Quantitative variation was found for the emission of the monoterpene (E)-b-ocimene, the sesquiterpene (E,E)-a-farnesene, the irregular homoterpene 4,8,12-trimethyltridecatetra-1,3,7,11-ene, and the benzenoid compound methyl salicylate. Differences in the relative emissions of (E)-b-ocimene and (E,E)-a-farnesene from accession Wassilewskija (Ws), a high-(E)-b-ocimene emitter, and accession Columbia (Col-0), a trace-(E)-b-ocimene emitter, were attributed to allelic variation of two closely related, tandem-duplicated terpene synthase genes, TPS02 and TPS03. The Ws genome contains a functional allele of TPS02 but not of TPS03, while the opposite is the case for Col-0. Recombinant proteins of the functional Ws TPS02 and Col-0 TPS03 genes both showed (E)-b-ocimene and (E,E)-a-farnesene synthase activities. However, differential subcellular compartmentalization of the two enzymes in plastids and the cytosol was found to be responsible for the ecotype-specific differences in (E)-b-ocimene/(E,E)-a-farnesene emission. Expression of the functional TPS02 and TPS03 alleles is induced in leaves by elicitor and insect treatment and occurs constitutively in floral tissues. Our studies show that both pseudogenization in the TPS family and subcellular segregation of functional TPS enzymes control the variation and plasticity of induced volatile emissions in wild plant species.

In Planta Variation of Volatile Biosynthesis: An Alternative Biosynthetic Route to the Formation of the Pathogen-Induced Volatile Homoterpene DMNT via Triterpene Degradation in Arabidopsis Roots

“…RNA was extracted using the TRI reagent (Fisher) (Huang et al, 2010) from axenically grown Col-0 roots treated with JA for 24 h. The amplified fragments were cloned into the pENTR/D-TOPO vector (Invitrogen). For construction of CaMV 35S overexpression lines, the ABDS and CYP705A1 cDNAs were subcloned into the pB7WG2 vector (Karimi et al, 2002) using LR recombination (Invitrogen).…”

“…Two micrograms of total RNA was treated with DNase I (Promega) and subsequently converted into cDNA using SuperScript II (Invitrogen) according to the manufacturer's instructions. The expression of P450 candidates in root tissues was monitored by RT-PCR according to Huang et al (2010) using gene-specific primers designed by Prime-BLAST (Ye et al, 2012) listed in Supplemental Table 4. Homozygous mutants were identified using PCR-based genotyping and full-length ABDS and CYP705A1 transcript expression was analyzed by RT-PCR using corresponding gene specific full-length primer pairs (Supplemental Table 4).…”

Gene Coexpression Analysis Reveals Complex Metabolism of the Monoterpene Alcohol Linalool inArabidopsisFlowers

“…Three other genes expressed almost exclusively in flowers were shown to encode enzymes producing (+)-(3S)-linalool (TPS14), (2)-(E)-b-caryophyllene and a-humulene (TPS21), a-pinene, sabinene, b-pinene, b-myrcene, limonene, and (E)-b-ocimene (TPS24) as main products (Chen et al, 2003). (E)-b-Ocimene and (E,E)-a-farnesene were produced in vitro by two enzymes encoded by other flower-expressed tandem duplicated paralogs: TPS3 (functional in the ecotype Col-0) and TPS2 (functional in Wassilewskija) (Fäldt et al, 2003;Huang et al, 2010). The respective in vivo activities of the latter, however, appeared modulated by its different subcellular localization (Huang et al, 2010).…”

“…(E)-b-Ocimene and (E,E)-a-farnesene were produced in vitro by two enzymes encoded by other flower-expressed tandem duplicated paralogs: TPS3 (functional in the ecotype Col-0) and TPS2 (functional in Wassilewskija) (Fäldt et al, 2003;Huang et al, 2010). The respective in vivo activities of the latter, however, appeared modulated by its different subcellular localization (Huang et al, 2010). Most of the floral sesquiterpene emission was found to rely on only two TPSs (TPS21 and TPS11), producing a complex blend with (2)-(E)-b-caryophyllene (TPS21), (+)-thujopsene, and (+)-b-chamigrene (TPS11) as main products (Tholl et al, 2005).…”

Alteration ofArabidopsis SLAC1promoter and its association with natural variation in drought tolerance

“…[21][22][23][24] Ozone-induced visible injury correlated with water loss from detached leaves 25 and Tamaoki et al 21 showed that Ws-2 is more susceptible to ozone than Col-0. Our results that Ws-2 is less tolerant to drought than Col-0 are in line with these findings.…”