Carotenoid Metabolism in Plants

Carotenoids are known to play important roles in plants as antioxidants, accessory light-harvesting pigments, and attractants for pollinators and seed dispersers. A new function for carotenoids has recently emerged, which relates to the response of plants to environmental stresses. Reactive oxygen species, especially singlet oxygen, produced in the chloroplasts under stress conditions, can oxidize carotenoids leading to a variety of oxidized products, including aldehydes, ketones, endoperoxides and lactones. Some of those carotenoid derivatives, such as volatile β-cyclocitral, derived from the oxidation of β-carotene, are reactive electrophile species that are bioactive and can induce changes in gene expression leading to acclimation to stress conditions. This review summarizes the current knowledge on the non-enzymatic oxidation of carotenoids, the bioactivity of the resulting cleavage compounds and their functions as stress signals in plants.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/tpj.12386

Carotenoid oxidation products as stress signals in plants.

Sas System For Mixed Models

Sites of synthesis, biochemistry and functional role of plant volatiles

Camelina uses, genetics, genomics, production, and management

A suite of commercially available volatile compounds was tested in an olfactometer bioassay for responses by the crucifer flea beetle (Phyllotreta cruciferae). Flea beetles were inhibited by exposure to hexane, pentane, and ethanol. Allyl-isothiocyanate, a crucifer-specific volatile, was moderately attractive to spring and early fall flea beetles, but inhibitory to late fall flea beetles. Spring flea beetles were most attracted to ( + )-sabinene and E-β-ocimene, and 1-hexanol, 1-pentanol, and Z-3-hexen-1-ol were stronger attractants than allyl-isothiocyanate. Spring beetles were strongly inhibited by ( - )-E-caryophyllene, β-ionone, indole, ( ± )-linalool, ( + )-limonene, E-geraniol, and ( - ) -β-pinene and moderately inhibited by ( - ) -verbenene and hexenal. Our study showed that older leaves and flowers of Brassica napus variety AC Excel contained small amounts of β-ionone, but seedlings did not. β-Ionone has not been documented previously in B. napus.

https://bioone.org/journals/Environmental-Entomology/volume-38/issue-5/022.038.0515/Responses-of-the-Crucifer-Flea-Beetle-to-Brassica-Volatiles-in/10.1603/022.038.0515.pdf

Responses of the crucifer flea beetle to Brassica volatiles in an olfactometer.

Laboratory and field studies were undertaken to determine the effects of increased numbers of trichomes on seedling stems, petioles, and first true leaves of Brassica napus L., canola, on the feeding and behavior of the crucifer flea beetle Phyllotreta cruciferae (Goeze) (Coleoptera: Chrysomelidae). Seedlings of ‘Westar’ canola with genes inserted from Arabidopsis thaliana L. for increased trichome production, called Hairy1, were tested against Westar seedlings in no-choice and choice laboratory tests, and against parental plants and other cultivars grown from seed with and without insecticide in field trials at Saskatoon and Lethbridge, Canada. Analyses of prefeeding and feeding behavior in no-choice tests of first true leaves found that flea beetles interacted with their host while off Hairy1 leaves more so than beetles presented with leaves of Westar. Beetles required twice as much time to reach satiation when feeding on leaves with increased pubescence than on Westar leaves. In laboratory choice tests, flea beetles fed more on cotyledons and second true leaves of Westar than on comparable tissues of the transgenic line. In field trials, variations in feeding patterns were seen over time on cotyledons of the line with elevated trichomes. However, all four young true leaves of Hairy1 seedlings were fed upon less than were the parental lines. Feeding on Hairy1 plants frequently occurred at levels equal to or less than on cultivars grown from insecticide-treated seed. This study highlights the first host plant resistance trait developed in canola, dense pubescence, with a strong potential to deter feeding by crucifer flea beetles.

https://bioone.org/journals/Journal-of-Economic-Entomology/volume-104/issue-1/EC10151/Feeding-by-Flea-Beetles-Coleoptera--Chrysomelidae-Phyllotreta-spp-is/10.1603/EC10151.pdf

Feeding by flea beetles (Coleoptera: Chrysomelidae; Phyllotreta spp.) is decreased on canola (Brassica napus) seedlings with increased trichome density.

In an investigation of Camelina sativa (Linnaeus) Crantz (Brassicaceae) and five common insect pests of canola (Brassica napus Linnaeus) (Brassicaceae), little feeding damage to the plant was inflicted by crucifer-feeding specialist flea beetles (Phyllotreta Chevrolat species) (Coleoptera: Chrysomelidae), Delia Robineau-Desvoidy (Diptera: Anthomyiidae) root maggots, or diamondback moth (Plutella xylostella Linnaeus (Lepidoptera: Plutellidae)). In choice tests, diamondback moths laid fewer eggs on C. sativa than on B. napus leaves. Diamondback moth larvae consumed less C. sativa leaf tissue, and tended to have a longer developmental period on C. sativa. Larvae of the polyphagous bertha armyworm (Mamestra configurata Walker (Lepidoptera: Noctuidae)) had similar feeding levels on C. sativa and B. napus plants. However, there was a longer developmental period from larval to pupal stage and pupae weighed less when fed on C. sativa foliage, suggesting that C. sativa contains antibiosis factors against bertha armyworm. Two strains of aster yellows phytoplasma, 16SrI-A and 16SrI-B, were identified in C. sativa and in Macrosteles quadrilineatus (Forbes) (Hemiptera: Cicadellidae). Differences in incidence of aster yellows and abundance of M. quadrilineatus were observed among lines of C. sativa. The findings confirm that C. sativa is unlikely to support high populations of these insect pests on the Canadian prairies.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0008347X1400042X

Interactions between Camelina sativa (Brassicaceae) and insect pests of canola

Crucifer-feeding flea beetles, Phyllotreta spp., are chronic insect pests in Canadian prairie canola production. Multiple laboratory and field feeding bioassays were conducted to determine the susceptibility of a wide range of crucifer species, cultivars, and accessions to feeding by flea beetles with the goal of discovering sources of resistant germplasm. In 62 bioassays of 218 entries, no consistent decreased feeding by flea beetles was seen on any entries of Brassica carinata A. Braun, Brassica juncea (L.) Czern., Brassica napus L., or Brassica rapa L. There was reduced feeding on condiment mustard Sinapis alba L. lines but not on canola-quality lines with reduced amounts of glucosinolates, which were fed on at levels equal to B. napus. Analyses of glucosinolate content found decreased quantities of hydroxybenzyl and butyl glucosinolates in preferred canola-quality S. alba lines and increased levels of hydroxybutenyl glucosinolates compared with levels in condiment S. alba lines. Eruca sativa Mill. was an excellent flea beetle host; Camelina sativa (L.) Crantz lines experienced little feeding. Lines of Crambe abyssinica Hochst. ex R. E. Fries and Crambe hispanica L. had reduced feeding levels compared with Brassica entries, but Crambe glabrata DC did not. The results indicate possible sources of resistance to Phyllotreta flea beetles, while highlighting the complicated roles that glucosinolates may play in Phyllotreta host preference.

https://bioone.org/journals/Journal-of-Economic-Entomology/volume-106/issue-6/EC13102/Susceptibility-of-Brassicaceous-Plants-to-Feeding-by-Flea-Beetles-Phyllotreta/10.1603/EC13102.pdf

Susceptibility of brassicaceous plants to feeding by flea beetles, Phyllotreta spp. (Coleoptera: Chrysomelidae).

Field studies were conducted at two locations on the Canadian prairies to investigate use of reduced ratios of insecticide-treated seed in controlling flea beetle (Coleoptera: Chrysomelidae, Phyllotreta spp.) damage to canola (Brassica napus L. and Brassica rapa L.). Five treatments were evaluated: bare seed control, fungicide-only (0X), and three ratios of insecticide plus fungicide in proportions of all (1X), two thirds (0.67X), or one third (0.33X) of the seeds coated with insecticide. Decreasing treated seed ratios by one third had no consistent deleterious effects on flea beetle damage, seedling growth, plant density, seed yield, or net cash return. Flea beetle injury to seedlings in the 1X treatment was similar to that of seedlings in the 0.67X treatment, with only two exceptions, and it was almost always lower than that of seedlings without insecticide. The 0.33X treatment generally had flea beetle feeding levels between those of the two high and the two noninsecticide treatments. Plant stand and seedling growth rates with 1X and 0.67X treatments were similar and higher than with bare seed or fungicide-alone treatments. Seed yields were inversely proportional to flea beetle feeding levels. Under very heavy flea beetle feeding, seed yields and net cash returns were highest in 1X plots, but when flea beetle feeding pressure was less extreme and canola growing conditions were favorable, 0.67X seed yields and profits from them were comparable to those in 1X treatments. On an economic basis, currently there is no advantage to decreasing the level of insecticide treated canola seed, but other considerations may affect this assessment.

https://bioone.org/journals/journal-of-economic-entomology/volume-101/issue-6/0022-0493-101.6.1811/Impact-of-Decreasing-Ratios-of-Insecticide-Treated-Seed-on-Flea/10.1603/0022-0493-101.6.1811.pdf

Impact of Decreasing Ratios of Insecticide-Treated Seed on Flea Beetle (Coleoptera: Chrysomelidae, Phyllotreta spp.) Feeding Levels and Canola Seed Yields

Larry Grenkow

Papers

Responses of the crucifer flea beetle to Brassica volatiles in an olfactometer.

Feeding by flea beetles (Coleoptera: Chrysomelidae; Phyllotreta spp.) is decreased on canola (Brassica napus) seedlings with increased trichome density.

Interactions between Camelina sativa (Brassicaceae) and insect pests of canola

Susceptibility of brassicaceous plants to feeding by flea beetles, Phyllotreta spp. (Coleoptera: Chrysomelidae).

Impact of Decreasing Ratios of Insecticide-Treated Seed on Flea Beetle (Coleoptera: Chrysomelidae, Phyllotreta spp.) Feeding Levels and Canola Seed Yields