EST-SSR analysis and cross-species transferability study in Lavandula

The genus Lavandula comprises of several economically important lavender species that are mainly cultivated worldwide for essential oil production. Identification of lavender species and their cultivars has been a huge bottleneck in lavender industries due to lack of appropriate identification mechanisms. Recent advances in modern technologies would help to address these identification issues through development of potential molecular markers, including simple sequence repeats (SSRs). SSRs can be developed from specific species, and can be potentially used for related species, which lack the source sequences to develop species-specific SSRs. Here, we describe the guidelines and steps of identifying and analyzing SSRs from expressed sequence tag (EST) sequences of lavender species. We also detail the validation procedures of selected EST-SSRs in distinguishing source (donor) species as well as related species.Arts and Sciences, Irving K. Barber School of (Okanagan)Non UBCBiology, Department of (Okanagan)ReviewedFacult

Identification, validation and cross-species transferability of novel Lavandula EST-SSRs

Main conclusion: We identified and characterized EST-SSRs with strong discrimination power against L. angustifolia and L. x intermedia species. The markers also showed considerable cross-species transferability rate into six related Lavandula species. Lavenders (Lavandula) are important economical crops grown around the globe for essential oil production. In an attempt to develop genetic markers for these plants, we analyzed over 13,000 unigenes developed from L. angustifolia and L. x intermedia EST databases, and identified 3,459 simple sequence repeats (SSR), which were dominated by trinucleotides (41.2%) and dinucleotides (31.45%). Approximately 19% of the unigenes contained at least one SSR marker, over 60% of which were localized in the UTRs. Only 252 EST-SSRs were 18 bp or longer from which 31 loci were validated, and 24 amplified discrete fragments with 85% polymorphism in L. x intermedia and L. angustifolia. The average number of alleles in L. x intermedia and L. angustifolia were 3.42 and 3.71 per marker with average PIC values of 0.47 and 0.52, respectively. These values suggest a moderate to strong level of informativeness for the markers, with some loci producing unique fingerprints. The cross-species transferability rate of the markers ranges in 50 to 100% across eight species. The utility of these markers was assessed in eight Lavandula species and 15 L. angustifolia and L. x intermedia cultivars, and the dendrogram deduced from their similarity indexes successfully delineated the species into their respective sections and the cultivars into their respective species. These markers have potential for application in fingerprinting, diversity studies and marker-assisted breeding of Lavandula. [This is a post-peer-review, pre-copyedit version of an article published in Planta. The final authenticated version is available online at: http://dx.doi.org/10.1007/s00425-014-2226-8].Arts and Sciences, Irving K. Barber School of (Okanagan)Biology, Department of (Okanagan)ReviewedFacult

Isolation and functional characterization of a methyl jasmonate-responsive 3-carene synthase from Lavandula x intermedia

A methyl jasmonate responsive 3-carene synthase (Li3CARS) gene was isolated from Lavandula x intermedia and functionally characterized in vitro. Lavenders produce essential oils consisting mainly of monoterpenes, including the potent antimicrobial and insecticidal monoterpene 3-carene. In this study we isolated and functionally characterized a leaf-specific, methyl jasmonate (MeJA)-responsive monoterpene synthase (Li3CARS) from Lavandula x intermedia. The ORF excluding transit peptides encoded a 64.9 kDa protein that was expressed in E. coli, and purified with Ni-NTA agarose affinity chromatography. The recombinant Li3CARS converted GPP into 3-carene as the major product, with K m and k cat of 3.69 ± 1.17 µM and 2.01 s-¹ respectively. Li3CARS also accepted NPP as a substrate to produce multiple products including a small amount of 3-carene. The catalytic efficiency of Li3CARS to produce 3-carene was over ten fold higher for GPP (k cat /K m = 0.56 µM-¹s-¹) than NPP (k cat /K m = 0.044 µM-¹s-¹). Production of distinct end product profiles from different substrates (GPP versus NPP) by Li3CARS indicates that monoterpene metabolism may be controlled in part through substrate availability. Li3CARS transcripts were found to be highly abundant in leaves (16-fold) as compared to flower tissues. The transcriptional activity of Li3CARS correlated with 3-carene production, and was up-regulated (1.18- to 3.8-fold) with MeJA 8-72 h post-treatment. The results suggest that Li3CARS may have a defensive role in Lavandula.Arts and Sciences, Irving K. Barber School of (Okanagan)Biology, Department of (Okanagan)ReviewedFacult

RNA-Seq in the discovery of a sparsely expressed scent-determining monoterpene synthase in lavenders (Lavandula)

Using RNA-Seq, we cloned and characterized a unique monoterpene synthase responsible for the formation of a scent-determining S-linalool constituent of lavender oils from Lavandula × intermedia. Several species of Lavandula produce essential oils (EOs) consisting mainly of monoterpenes including linalool, one of the most abundant and scent-determining oil constituents. Although R-linalool dominates the EOs of lavenders, varying amounts (depending on the species) of the S-linalool enantiomer can also be found in these plants. Despite its relatively low abundance, S-linalool contributes a sweet, pleasant scent and is an important constituent of lavender EOs. While several terpene synthase genes including R-linalool synthase have been cloned from lavenders many important terpene synthases including S-linalool synthase have not been described from these plants. In this study, we employed RNA-Seq and other complementary sequencing data to clone and functionally characterize the sparsely expressed S-linalool synthase cDNA (LiS-LINS) from Lavandula × intermedia. Recombinant LiS-LINS catalyzed the conversion of the universal monoterpene precursor geranyl diphosphate to S-linalool as the sole product. Intriguingly, LiS-LINS exhibited very low (~ 30%) sequence similarity to other Lavandula terpene synthases, including R-linalool synthase. However, the predicted 3D structure of this protein, including the composition and arrangement of amino acids at the active site, is highly homologous to known terpene synthase proteins. LiS-LINS transcripts were detected in flowers, but were much less abundant than those corresponding to LiR-LINS, paralleling enantiomeric composition of linalool in L. × intermedia oils. These data indicate that production of S-linalool is at least partially controlled at the level of transcription from LiS-LINS. The cloned LiS-LINS cDNA may be used to enhance oil composition in lavenders and other plants through metabolic engineering. [This is a post-peer-review, pre-copyedit version of an article published in Planta. The final authenticated version is available online at: http://dx.doi.org/10.1007/s00425-018-2935-5]Arts and Sciences, Irving K. Barber School of (Okanagan)Non UBCBiology, Department of (Okanagan)ReviewedFacult