Terpene produced by coexpression of the TPS and P450 genes from Lavandula angustifolia protects plants from herbivore attacks during budding stages.

To deter herbivore attacks, plants employ a diverse array of volatile compounds, particularly during the early developmental stages. The highly expressed genes LaTPS7, LaTPS8, and LaCYP71D582 were identified during the budding phases of Lavandula angustifolia. In vitro studies revealed that LaTPS7 generated nine distinct compounds, including camphene, myrcene, and limonene. LaTPS8 enzymatically converted eight volatiles by utilizing geranyl diphosphate and nerolidyl diphosphate as substrates. Overexpression of plastid-localized LaTPS7 in Nicotiana benthamiana resulted in the production of limonene. Furthermore, the endoplasmic reticulum-associated enzyme LaCYP71D582 potentially converted limonene into carveol. In N. benthamiana, LaTPS8 is responsible for the synthesis of α-pinene and sylvestrene. Furthermore, leaves transfected with LaTPS7 and leaves cotransfected with LaTPS7 and LaCYP71D582 exhibited a repellent effect on aphids, with an approximate rate of 70%. In comparison, leaves with an empty vector displayed a repellent rate of approximately 20%. Conversely, tobacco leaves expressing LaTPS7 attracted ladybugs at a rate of 48.33%, while leaves coexpressing LaTPS7 and LaCYP71D582 attracted ladybugs at a slightly higher rate of 58.33%. Subsequent authentic standard tests confirmed that limonene and carveol repel Myzus persicae while attracting Harmonia axyridis. The promoter activity of LaTPS7 and LaCYP71D582 was evaluated in Arabidopsis thaliana using GUS staining, and it was observed that wounding stimulated the expression of LaTPS7. The volatile compounds produced by LaTPS7, LaTPS8, and LaCYP71D582 play a crucial role in plant defence mechanisms. In practical applications, employing biological control measures based on plant-based approaches can promote human and environmental health.

Decoupling subgenomes within hybrid lavandin provide new insights into speciation and monoterpenoid diversification of Lavandula.

Polyploidization and transposon elements contribute to shape plant genome diversity and secondary metabolic variation in some edible crops. However, the specific contribution of these variations to the chemo-diversity of Lamiaceae, particularly in economic shrubs, is still poorly documented. The rich essential oils (EOs) of Lavandula plants are distinguished by monoterpenoids among the main EO-producing species, L. angustifolia (LA), L. × intermedia (LX) and L. latifolia (LL). Herein, the first allele-aware chromosome-level genome was assembled using a lavandin cultivar 'Super' and its hybrid origin was verified by two complete subgenomes (LX-LA and LX-LL). Genome-wide phylogenetics confirmed that LL, like LA, underwent two lineage-specific WGDs after the γ triplication event, and their speciation occurred after the last WGD. Chloroplast phylogenetic analysis indicated LA was the maternal source of 'Super', which produced premium EO (higher linalyl/lavandulyl acetate and lower 1,8-cineole and camphor) close to LA. Gene expression, especially the monoterpenoid biosynthetic genes, showed bias to LX-LA alleles. Asymmetric transposon insertions in two decoupling 'Super' subgenomes were responsible for speciation and monoterpenoid divergence of the progenitors. Both hybrid and parental evolutionary analysis revealed that LTR (long terminal repeat) retrotransposon associated with AAT gene loss cause no linalyl/lavandulyl acetate production in LL, and multi-BDH copies retained by tandem duplication and DNA transposon resulted in higher camphor accumulation of LL. Advances in allelic variations of monoterpenoids have the potential to revolutionize future lavandin breeding and EO production.

Full-length transcriptome-referenced analysis reveals crucial roles of hormone and wounding during induction of aerial bulbils in lily.

Aerial bulbils are important vegetative reproductive organs in Lilium. They are often perpetually dormant in most Lilium species, and little is known about the induction of these vegetative structures. The world-famous Oriental hybrid lily cultivar 'Sorbonne', which blooms naturally devoid of aerial bulbils, is known for its lovely appearance and sweet fragrance. We found that decapitation stimulated the outgrowth of aerial bulbils at lower stems (LSs) and then application of low and high concentrations of IAA promoted aerial bulbils emergence around the wound at upper stems (USs) of 'Sorbonne'. However, the genetic basis of aerial bulbil induction is still unclear. Herein, 'Sorbonne' transcriptome has been sequenced for the first time using the combination of third-generation long-read and next-generation short-read technology. A total of 46,557 high-quality non-redundant full-length transcripts were generated. Transcriptomic profiling was performed on seven tissues and stems with treatments of decapitation and application of low and high concentrations of IAA, respectively. Functional annotation of 1918 DEGs within stem samples of different treatments showed that hormone signaling, sugar metabolism and wound-induced genes were crucial to bulbils outgrowth. The expression pattern of auxin-, shoot branching hormone-, plant defense hormone- and wound-inducing-related genes indicated their crucial roles in bulbil induction. Then we established five hormone- and wounding-regulated co-expression modules and identified some candidate transcriptional factors, such as MYB, bZIP, and bHLH, that may function in inducing bulbils. High connectivity was observed among hormone signaling genes, wound-induced genes, and some transcriptional factors, suggesting wound- and hormone-invoked signals exhibit extensive cross-talk and regulate bulbil initiation-associated genes via multilayered regulatory cascades. We propose that the induction of aerial bulbils at LSs after decapitation can be explained as the release of apical dominance. In contrast, the induction of aerial bulbils at the cut surface of USs after IAA application occurs via a process similar to callus formation. This study provides abundant candidate genes that will deepen our understanding of the regulation of bulbil outgrowth, paving the way for further molecular breeding of lily.

Time-series transcriptome provides insights into the gene regulation network involved in the volatile terpenoid metabolism during the flower development of lavender.

BACKGROUND: Essential oils (EOs) of Lavandula angustifolia, mainly consist of monoterpenoids and sesquiterpenoids, are of great commercial value. The multi-flower spiciform thyrse of lavender not only determines the output of EOs but also reflects an environmental adaption strategy. With the flower development and blossom in turn, the fluctuation of the volatile terpenoids displayed a regular change at each axis. However, the molecular mechanism underlying the regulation of volatile terpenoids during the process of flowering is poorly understood in lavender. Here, we combine metabolite and RNA-Seq analyses of flowers of five developmental stages at first- and second-axis (FFDSFSA) and initial flower bud (FB0) to discover the active terpenoid biosynthesis as well as flowering-related genes. RESULTS: A total of 56 mono- and sesquiterpenoids were identified in the EOs of L. angustifolia 'JX-2'. FB0' EO consists of 55 compounds and the two highest compounds, ß-trans-ocimene (20.57%) and (+)-R-limonene (17.00%), can get rid of 74.71 and 78.41% aphids in Y-tube olfactometer experiments, respectively. With sequential and successive blossoms, temporally regulated volatiles were linked to pollinator attraction in field and olfaction bioassays. In three characteristic compounds of FFDSFSA' EOs, linalyl acetate (72.73%) and lavandulyl acetate (72.09%) attracted more bees than linalool (45.35%). Many transcripts related to flowering time and volatile terpenoid metabolism expressed differently during the flower development. Similar metabolic and transcriptomic profiles were observed when florets from the two axes were maintained at the same maturity grade. Besides both compounds and differentially expressed genes were rich in FB0, most volatile compounds were significantly correlated with FB0-specific gene module. Most key regulators related to flowering and terpenoid metabolism were interconnected in the subnetwork of FB0-specific module, suggesting the cross-talk between the two biological processes to some degree. CONCLUSIONS: Characteristic compounds and gene expression profile of FB0 exhibit ecological value in pest control. The precise control of each-axis flowering and regular emissions at transcriptional and metabolic level are important to pollinators attraction for lavender. Our study sheds new light on lavender maximizes its fitness from "gene-volatile terpenoid-insect" three layers.

Overexpression of Poplar PtrWRKY89 in Transgenic Arabidopsis Leads to a Reduction of Disease Resistance by Regulating Defense-Related Genes in Salicylate- and Jasmonate-Dependent Signaling.

The plant hormones jasmonic acid (JA) and salicylic acid (SA) play key roles in plant defenses against pathogens and several WRKY transcription factors have been shown to have a role in SA/JA crosstalk. In a previous study, overexpression of the poplar WRKY gene PtrWRKY89 enhanced resistance to pathogens in transgenic poplars. In this study, the promoter of PtrWRKY89 (ProPtrWRKY89) was isolated and used to drive GUS reporter gene. High GUS activity was observed in old leaves of transgenic Arabidopsis containing ProPtrWRKY89-GUS construct and GUS expression was extremely induced by SA solution and SA+MeJA mixture but not by MeJA treatment. Subcellular localization and transactivation assays showed that PtrWRKY89 acted as a transcription activator in the nucleus. Constitutive expression of PtrWRKY89 in Arabidopsis resulted in more susceptible to Pseudomonas syringae and Botrytis cinerea compared to wild-type plants. Quantitative real-time PCR (qRT-PCR) analysis confirmed that marker genes of SA and JA pathways were down-regulated in transgenic Arabidopsis after pathogen inoculations. Overall, our results indicated that PtrWRKY89 modulates a cross talk in resistance to P. syringe and B. cinerea by negatively regulating both SA and JA pathways in Arabidopsis.

Isolation and characterization of a subgroup IIa WRKY transcription factor PtrWRKY40 from Populus trichocarpa.

Salicylic acid (SA) is a defense-related key signaling molecule involved in plant immunity. In this study, a subgroup IIa WRKY gene PtrWRKY40 was isolated from Populus trichocarpa, which displayed amino acid sequence similar to Arabidopsis AtWRKY40, AtWRKY18 and AtWRKY60. PtrWRKY40 transcripts accumulated significantly in response to SA, methyl jasmonate and hemibiotrophic fungus Dothiorella gregaria Sacc. Overexpression of PtrWRKY40 in transgenic poplar conferred higher susceptibility to D. gregaria infection. This susceptibility was coupled with reduced expression of SA-associated genes (PR1.1, PR2.1, PR5.9, CPR5 and SID2) and jasmonic acid (JA)-related gene JAZ8. Decreased accumulation of endogenous SA was observed in transgenic lines overexpressing PtrWRKY40 when compared with wild-type plants. However, constitutive expression of PtrWRKY40 in Arabidopsis thaliana displayed resistance to necrotrophic fungus Botrytis cinerea, and the expression of JA-defense-related genes such as PDF1.2, VSP2 and PR3 was remarkably increased in transgenic plants upon infection with fugal pathogens. Together, our findings indicate that PtrWRKY40 plays a negative role in resistance to hemibiotrophic fungi in poplar but functions as a positive regulator of resistance toward the necrotrophic fungi in Arabidopsis.

PtrWRKY73, a salicylic acid-inducible poplar WRKY transcription factor, is involved in disease resistance in Arabidopsis thaliana.

KEY MESSAGE: A salicylic acid-inducible WRKY gene, PtrWRKY73, from Populus trichocarpa , was isolated and characterized. Overexpression of PtrWRKY73 in Arabidopsis thaliana increased resistance to biotrophic pathogens but reduced resistance against necrotrophic pathogens. WRKY transcription factors are commonly involved in plant defense responses. However, limited information is available about the roles of the WRKY genes in poplar defense. In this study, we isolated a salicylic acid (SA)-inducible WRKY gene, PtrWRKY73, from Populus trichocarpa, belonging to group I family and containing two WRKY domains, a D domain and an SP cluster. PtrWRKY73 was expressed predominantly in roots, old leaves, sprouts and stems, especially in phloem and its expression was induced in response to treatment with exogenous SA. PtrWRKY73 was localized to the nucleus of plant cells and exhibited transcriptional activation. Overexpression of PtrWRKY73 in Arabidopsis thaliana resulted in increased resistance to a virulent strain of the bacterial pathogen Pseudomonas syringae (PstDC3000), but more sensitivity to the necrotrophic fungal pathogen Botrytis cinerea. The SA-mediated defense-associated genes, such as PR1, PR2 and PAD4, were markedly up-regulated in transgenic plants overexpressing PtrWRKY73. Arabidopsis non-expressor of PR1 (NPR1) was not affected, whereas a defense-related gene PAL4 had reduced in PtrWRKY73 overexpressor plants. Together, these results indicated that PtrWRKY73 plays a positive role in plant resistance to biotrophic pathogens but a negative effect on resistance against necrotrophic pathogens.