Terpene chemotypes in Gossypium hirsutum (wild cotton) from the Yucatan Peninsula, Mexico

Cotton (Gossypium hirsutum) stores defensive compounds in glands covering its leaves and other tissues. The density and the chemical filling of these glands increase systematically in developing leaves in response to herbivory on older leaves. Cotton seedlings are known to respond more strongly to actual caterpillar herbivory than to mere physical damage. It is not clear whether this amplified response is linked to insect-derived elicitors or difference in damage properties. To investigate this, we assessed the effect of repeated artificial damage without and with application of regurgitant from Spodoptera exigua caterpillars. Repeated mechanical damage led to a systemic increase of gland density, gland size, and content of defensive terpenes, with no detectable additional elicitation upon regurgitant treatment. Dual choice feeding assays further showed that defense induction triggered by just physical damage made newly developing leaves far less palatable to S. exigua larvae as compared to leaves from undamaged seedlings, whereas they did not distinguish between leaves from damaged plants treated with or without regurgitant. Our study confirms that the systemic induction of cotton glands is an unspecific response to physical damage, although cotton is known to respond to caterpillar-associated elicitors for other defensive traits. Cotton glands induction can be readily visualized under modest magnification, making the experiments described in this study highly suited to teach chemical ecology and aspects of plant defense theory in practical classes.

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“…We used the same procedure as described by Clancy et al (2023). 100 mg of frozen leaf powder were extracted with 1 mL of hexane.…”

Section: Volatile Terpenesmentioning

confidence: 99%

Cotton plants as ideal models for teaching and research on inducible direct plant defenses

Mamin

Vallat²,

Turlings³

2023

Front. Ecol. Evol.

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“…Wild Gossypium hirsutum seeds were collected in 2019 and 2020 on the northern coast of the Yucatán Peninsula (Mexico) and grown as described in Clancy et al (2023). Seeds were sampled from several mother plants from 16 populations in four regions along the coast (Table S1 and Fig.…”

Section: Plants and Insectsmentioning

confidence: 99%

“…Hexane leaf extractions and subsequent analyzes were performed as described in Clancy et al (2023). Briefly, 100 mg of grounded frozen leaf material was extracted with 1 mL of hexane and kept at 4 °C for 24 hours.…”

Section: Hexane Leaf Extractions and Gc-ms Analysesmentioning

confidence: 99%

“…G. hirsutum was domesticated at least 4,000 years ago in the Yucatán Peninsula (southeast Mexico) (Yuan et al, 2021), where wild populations still grow naturally along its northern coastline (Wegier et al, 2011; Coppens d’Eeckenbrugge and Lacape, 2014). Recently, we described two heritable constitutive leaf-terpene chemotypes in wild cotton plants from the Yucatan coast: one chemotype containing none or low amounts of γ-terpinene (and other coexpressed monoterpenes), and the other exhibiting distinctively higher abundances of these compounds in their leaves (Clancy et al, 2023). It is worthwhile to note that production of γ-terpinene has been only described in wild/naturalized cotton (Loughrin et al, 1995; Hagenbucher et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Induction by caterpillars of stored and emitted volatiles in terpene chemotypes from populations of wild cotton (Gossypium hirsutum)

Mamin,

Clancy,

Flückiger

et al. 2024

Preprint

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Upland cotton (Gossypium hirsutum) plants constitutively store volatile terpenes in their leaves, which are steadily emitted at low levels. Herbivory leads to a greater release of these stored volatiles. Additionally, damaged plants increase terpene accumulation and emit other terpenes and additional volatiles. This has been well characterised for cultivated cotton, but little is known about volatile emissions in wild cotton. We investigated how herbivory by the beet armyworm (Spodoptera exigua) affects both leaf-stored and emitted volatiles in wild cotton plants from populations found along the Yucatan coast and assessed different scales of intraspecific variation in induced volatiles. Furthermore, we examined how leaf-terpene chemotypes differ in volatile emissions from intact and damaged plants. Herbivory triggered changes in stored and emitted volatiles in a manner similar to what is known for cultivated cotton. However, we report for the first time the emission of volatile aldoximes by cotton plants, which were only detected in the headspace upon herbivory, and displayed interpopulation variation. Intraspecific variation was also observed in the induced emissions of nitriles and some terpenes. In addition, chemotypes differed in their induction of the (E)-beta-ocimene in leaves. Distinctions between terpene chemotypes were reflected in the emissions from both intact and damaged plants, suggesting differences in how dominant terpenes of each chemotype might affect airborne interactions. However, these variable terpenes showed weak inducibility, raising questions about their functions. This comprehensive insight into herbivore-induced volatiles in wild cotton may help in the development of future pest-management strategies for cotton crops.

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“…These chemical variations can have significant ecological consequences for a species, for example by affecting a plant's susceptibility to specialised herbivores and pathogens, or its tolerance to adverse environmental conditions (Thompson et al ., 2013; Bustos‐Segura et al ., 2015). Spatial patterning in natural populations and segregation of chemotypes in biparental crosses suggests large genetic factors underly these chemical polymorphisms (Karban et al ., 2014; Clancy et al ., 2023), but rarely has the genetic architecture contributing to the coordinated fluctuation in terpene components been unravelled. In the Mediterranean shrub Thymus vulgaris , nucleotide polymorphisms within TPS genes were recently found to associate with ecotype and chemotype variations (Bataillon et al ., 2022), but how these genes are organised within the genome and control segregating chemotypes is still unknown.…”

Section: Introductionmentioning

confidence: 99%

A terpene synthase supergene locus determines chemotype in Melaleuca alternifolia (tea tree)

Voelker,

Mauleon,

Shepherd

2023

New Phytologist

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Summary Leaf oil terpenes vary categorically in many plant populations, leading to discrete phenotypes of adaptive and economic significance, but for most species, a genetic explanation for the concerted fluctuation in terpene chemistry remains unresolved. To uncover the genetic architecture underlying multi‐component terpene chemotypes in Melaleuca alternifolia (tea tree), a genome‐wide association study was undertaken for 148 individuals representing all six recognised chemotypes. A number of single nucleotide polymorphisms in a genomic region of c. 400 kb explained large proportions of the variation in key monoterpenes of tea tree oil. The region contained a cluster of 10 monoterpene synthase genes, including four genes predicted to encode synthases for 1,8‐cineole, terpinolene, and the terpinen‐4‐ol precursor, sabinene hydrate. Chemotype‐dependent null alleles at some sites suggested structural variants within this gene cluster, providing a possible basis for linkage disequilibrium in this region. Genotyping in a separate domesticated population revealed that all alleles surrounding this gene cluster were fixed after artificial selection for a single chemotype. These observations indicate that a supergene accounts for chemotypes in M. alternifolia. A genetic model with three haplotypes, encompassing the four characterised monoterpene synthase genes, explained the six terpene chemotypes, and was consistent with available biparental cross‐segregation data.

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Terpene chemotypes in Gossypium hirsutum (wild cotton) from the Yucatan Peninsula, Mexico

Cited by 13 publications

References 56 publications

Cotton plants as ideal models for teaching and research on inducible direct plant defenses

Cotton plants as ideal models for teaching and research on inducible direct plant defenses

Induction by caterpillars of stored and emitted volatiles in terpene chemotypes from populations of wild cotton (Gossypium hirsutum)

A terpene synthase supergene locus determines chemotype in Melaleuca alternifolia (tea tree)

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