Attract Insect Pollinators Research Articles

A novel O-methyltransferase Cp4MP-OMT catalyses the final step in the biosynthesis of the volatile 1,4-dimethoxybenzene in pumpkin (Cucurbita pepo) flowers

BackgroundFloral scents play a crucial role in attracting insect pollinators. Among the compounds attractive to pollinators is 1,4-dimethoxybenzene (1,4-DMB). It is a significant contributor to the scent profile of plants from various genera, including economically important Cucurbita species. Despite its importance, the biosynthetic pathway for the formation of 1,4-DMB was not elucidated so far.ResultsIn this study we showed the catalysis of 1,4-DMB in the presence of 4-methoxyphenol (4-MP) by protein extract from Styrian oil pumpkin (Cucurbita pepo) flowers. Based on this finding, we identified a novel O-methyltransferase gene, Cp4MP-OMT, whose expression is highly upregulated in the volatile-producing tissue of pumpkin flowers when compared to vegetative tissues. OMT activity was verified by purified recombinant Cp4MP-OMT, illustrating its ability to catalyse the methylation of 4-MP to 1,4-DMB in the presence of cofactor SAM (S-(5′-adenosyl)-L-methionine).ConclusionsCp4MP-OMT is a novel O-methyltransferase from C. pepo, responsible for the final step in the biosynthesis of the floral scent compound 1,4-DMB. Considering the significance of 1,4-DMB in attracting insects for pollination and in the further course fruit formation, enhanced understanding of its biosynthetic pathways holds great promise for both ecological insights and advancements in plant breeding initiatives.

Eco-evolutionary dynamics in two-species mutualistic systems: one-sided population decline triggers joint interaction disinvestment

The interplay between ecological and evolutionary dynamics can create feedback that reinforces external disturbances and potentially threatens species’ coexistence. For example, plants might invest less into attracting insect pollinators (decreased flower or nectar production) and more into independence (increased selfing or vegetative reproduction) when faced with pollinator decline. This adaptive response saves plant resources at the cost of further threatening the pollinator population. We ask under which conditions such self-reinforcing feedback occurs in two-species mutualistic systems when considering one-sided population decline and whether it can be counteracted by self-dampening feedback if co-evolution of both interaction partners is considered. Based on a mathematical model and in line with previous studies, we find that the described pattern of accelerated population decline occurs for a wide range of parameter values if a concave allocation trade-off between independent growth and interaction investment is assumed. The undisturbed population typically disinvests first, which then forces the declining population to also disinvest, in favour of other energy sources. However, a decelerated population decline can occur if the adaptation of the undisturbed partner is relatively slow compared to environmental decay, reducing the speed of its disinvestment, or if the initial investment into the interaction was very high. Our results suggest that if actions are taken to save endangered populations, not only the evolution of the target species but also of their interaction partner, as well as the interaction between them should be considered.

Pollinators and Other Insect Visitations on Native and Ornamental Perennials in Two Landscapes

Many pollinator insects, especially honey bees [Apis mellifera Linnaeus (Apidae)] and wild bees, are experiencing population decline because of forage and habitat losses. Planting perennial flowering taxa is one method of increasing pollinator habitat. The objectives of this study were to evaluate the potential of 27 native species and ornamental perennial cultivars to determine their ability to attract insect pollinators in a rural and an urban landscape in North Dakota, assess the potential of these perennials to attract other beneficial insects and insect pests, and identify the bee species visiting these perennials. Five to eight native species and/or ornamental cultivars each from four genera, Monarda L. (bee balm), Hylotelephium H. Ohba (stonecrop), Baptisia Vent. (wild indigo), and Symphyotrichum Nees (aster), were tested. Weekly observations of individual plants during flowering and their pollinator visitations from 2018 to 2020 indicated that insect pollinators were present for the earliest flowering perennials in June and until the latest flowering perennials during the second week of October or the first freeze. A total of 16,194 insect pollinators were observed, and 87.8% of these pollinator visitations were Hymenoptera and Diptera. Significant landscapes × perennial flowering taxa interactions were detected for all insect groups, except for syrphid flies, for which both main effects were significantly different. Overall, honey bees and beetles preferred to visit Hylotelephium and Symphyotrichum. The wild bees, lepidopterans, and syrphids preferred Hylotelephium, Symphyotrichum, and Monarda. Tachinids preferred Symphyotrichum. Blow flies preferred Hylotelephium. More beneficial insect visitations (i.e., 96.0%) and fewer insect pest visitations (i.e., 30.4%) were counted on the rural landscape. A total of 3311 bee individuals were identified as species from the following families: Apidae, Andrenidae, Colletidae, Megachilidae, and Halictidae. Thirty-one and 21 bee species were unique to the rural and urban landscapes, respectively. The two most common wild bees were Ceratina calcarata Robertson on the cultivar S. oblongifolium (Nutt.) G.L. Nessom October Skies and Lasioglossum imitatum (Smith) on some Monarda and Hylotelephium. These findings suggest that pollinator visitations are influenced by the landscape and varied among the perennial flowering taxa in some cases. However, all evaluated perennial flower taxa would be suitable for attracting and supporting pollinators in rural or urban landscape settings in the northern Great Plains.

Chemical profile and analysis of biosynthetic pathways and genes of volatile terpenes in Pityopsis ruthii, a rare and endangered flowering plant.

It is critical to gather biological information about rare and endangered plants to incorporate into conservation efforts. The secondary metabolism of Pityopsis ruthii, an endangered flowering plant that only occurs along limited sections of two rivers (Ocoee and Hiwassee) in Tennessee, USA was studied. Our long-term goal is to understand the mechanisms behind P. ruthii's adaptation to restricted areas in Tennessee. Here, we profiled the secondary metabolites, specifically in flowers, with a focus on terpenes, aiming to uncover the genomic and molecular basis of terpene biosynthesis in P. ruthii flowers using transcriptomic and biochemical approaches. By comparative profiling of the nonpolar portion of metabolites from various tissues, P. ruthii flowers were rich in terpenes, which included 4 monoterpenes and 10 sesquiterpenes. These terpenes were emitted from flowers as volatiles with monoterpenes and sesquiterpenes accounting for almost 68% and 32% of total emission of terpenes, respectively. These findings suggested that floral terpenes play important roles for the biology and adaptation of P. ruthii to its limited range. To investigate the biosynthesis of floral terpenes, transcriptome data for flowers were produced and analyzed. Genes involved in the terpene biosynthetic pathway were identified and their relative expressions determined. Using this approach, 67 putative terpene synthase (TPS) contigs were detected. TPSs in general are critical for terpene biosynthesis. Seven full-length TPS genes encoding putative monoterpene and sesquiterpene synthases were cloned and functionally characterized. Three catalyzed the biosynthesis of sesquiterpenes and four catalyzed the biosynthesis of monoterpenes. In conclusion, P. ruthii plants employ multiple TPS genes for the biosynthesis of a mixture of floral monoterpenes and sesquiterpenes, which probably play roles in chemical defense and attracting insect pollinators alike.

The Saururus chinensis genome provides insights into the evolution of pollination strategies and herbaceousness in magnoliids.

Saururus chinensis, an herbaceous magnoliid without perianth, represents a clade of early-diverging angiosperms that have gone through woodiness-herbaceousness transition and pollination obstacles: the characteristic white leaves underneath inflorescence during flowering time are considered a substitute for perianth to attract insect pollinators. Here, using the newly sequenced S. chinensis genome, we revisited the phylogenetic position of magnoliids within mesangiosperms, and recovered a sister relationship for magnoliids and Chloranthales. By considering differentially expressed genes, we identified candidate genes that are involved in the morphogenesis of the white leaves in S. chinensis. Among those genes, we verified - in a transgenic experiment with Arabidopsis - that increasing the expression of the "pseudo-etiolation in light" gene (ScPEL) can inhibit the biosynthesis of chlorophyll. ScPEL is thus likely responsible for the switches between green and white leaves, suggesting that changes in gene expression may underlie the evolution of pollination strategies. Despite being an herbaceous plant, S. chinensis still has vascular cambium and maintains the potential for secondary growth as a woody plant, because the necessary machinery, i.e., the entire gene set involved in lignin biosynthesis, is well preserved. However, similar expression levels of two key genes (CCR and CAD) between the stem and other tissues in the lignin biosynthesis pathway are possibly associated with the herbaceous nature of S. chinensis. In conclusion, the S. chinensis genome provides valuable insights into the adaptive evolution of pollination in Saururaceae and reveals a possible mechanism for the evolution of herbaceousness in magnoliids.

The reproductive biology of glossopterid gymnosperms—A review

We review recent advances on glossopterid reproductive biology and their implications for seed plant phylogeny and the ecology of this widespread Permian Gondwanan group. Microsporangiate organs are interpreted to have been arranged in loose compound cones—an organization that evokes comparisons with Ginkgoales, Cordaitales and early conifers. The pollen was typically taeniate, bisaccate, and primarily adapted to wind dispersal. The diverse ovuliferous organs generally incorporated some form of marginal flange or wing. In most cases, the wing was probably protective, wrapping around the ovules during early development. However, we postulate that some conspicuous flanges were potentially analogous to angiosperm petals, functioning as corolla-like guides to attract insect pollinators. The arrangement of seed-bearing polysperms adnate to the subtending leaf to form a fertiliger in glossopterids represented another means of protecting the ovules. In some cases, highlighting the polysperm against the attached leaf might have increased the showiness of the ovule-bearing part for pollinators. In other cases, detachment of the fertiliger may have aided anemochory by retarding seed fall through rotation analogous to dispersal in extant Tilia. The microgametophyte in glossopterids is characterized by a short, weakly branched, haustorial tube, and the release of motile sperm cells. At least some seeds of glossopterids express polyembryony. Mature seeds possessed various micropylar modifications for the entrapment of pollen, and winged or bulbous expansions of the outer integument to aid anemochory or possibly hydrochory. Vegetative regeneration as a response to damage occurred via epicormic buds and possibly by the development of lignotubers.

Nectar-dwelling microbes of common tansy are attractive to its mosquito pollinator, Culex pipiens L.

BackgroundThere is widespread interkingdom signalling between insects and microbes. For example, microbes found in floral nectar may modify its nutritional composition and produce odorants that alter the floral odor bouquet which may attract insect pollinators. Mosquitoes consume nectar and can pollinate flowers. We identified microbes isolated from nectar of common tansy, Tanacetum vulgare, elucidated the microbial odorants, and tested their ability to attract the common house mosquito, Culex pipiens.ResultsWe collected 19 microbial isolates from T. vulgare nectar, representing at least 12 different taxa which we identified with 16S or 26S rDNA sequencing as well as by biochemical and physiological tests. Three microorganisms (Lachancea thermotolerans, Micrococcus lactis, Micrococcus luteus) were grown on culture medium and tested in bioassays. Only the yeast L. thermotolerans grown on nectar, malt extract agar, or in synthetic nectar broth significantly attracted Cx. pipiens females. The odorant profile produced by L. thermotolerans varied with the nutritional composition of the culture medium. All three microbes grown separately, but presented concurrently, attracted fewer Cx. pipiens females than L. thermotolerans by itself.ConclusionsFloral nectar of T. vulgare contains various microbes whose odorants contribute to the odor profile of inflorescences. In addition, L. thermotolerans produced odorants that attract Cx. pipiens females. As the odor profile of L. thermotolerans varied with the composition of the culture medium, we hypothesize that microbe odorants inform nectar-foraging mosquitoes about the availability of certain macro-nutrients which, in turn, affect foraging decisions by mosquitoes.

Pseudoflowers produced by Fusarium xyrophilum on yellow-eyed grass (Xyris spp.) in Guyana: A novel floral mimicry system?

Pseudoflower formation is arguably the rarest outcome of a plant-fungus interaction. Here we report on a novel putative floral mimicry system in which the pseudoflowers are composed entirely of fungal tissues in contrast to modified leaves documented in previous mimicry systems. Pseudoflowers on two perennial Xyris species (yellow-eyed grass, X. setigera and X. surinamensis) collected from savannas in Guyana were produced by Fusarium xyrophilum, a novel Fusarium species. These pseudoflowers mimic Xyris flowers in gross morphology and are ultraviolet reflective. Axenic cultures of F. xyrophilum produced two pigments that had fluorescence emission maxima in light ranges that trichromatic insects are sensitive to and volatiles known to attract insect pollinators. One of the volatiles emitted by F. xyrophilum cultures (i.e., 2-ethylhexanol) was also detected in the head space of X. laxifolia var. iridifolia flowers, a perennial species native to the New World. Results of microscopic and PCR analyses, combined with examination of gross morphology of the pseudoflowers, provide evidence that the fungus had established a systemic infection in both Xyris species, sterilized them and formed fungal pseudoflowers containing both mating type idiomorphs. Fusarium xyrophilum cultures also produced the auxin indole-3-acetic acid (IAA) and the cytokinin isopentenyl adenosine (iPR). Field observations revealed that pseudoflowers and Xyris flowers were both visited by bees. Together, the results suggest that F. xyrophilum pseudoflowers are a novel floral mimicry system that attracts insect pollinators, via visual and olfactory cues, into vectoring its conidia, which might facilitate outcrossing of this putatively heterothallic fungus and infection of previously uninfected plants.

Australian native flower colours: Does nectar reward drive bee pollinator flower preferences?

Colour is an important signal that flowering plants use to attract insect pollinators like bees. Previous research in Germany has shown that nectar volume is higher for flower colours that are innately preferred by European bees, suggesting an important link between colour signals, bee preferences and floral rewards. In Australia, flower colour signals have evolved in parallel to the Northern hemisphere to enable easy discrimination and detection by the phylogenetically ancient trichromatic visual system of bees, and native Australian bees also possess similar innate colour preferences to European bees. We measured 59 spectral signatures from flowers present at two preserved native habitats in South Eastern Australia and tested whether there were any significant differences in the frequency of flowers presenting higher nectar rewards depending upon the colour category of the flower signals, as perceived by bees. We also tested if there was a significant correlation between chromatic contrast and the frequency of flowers presenting higher nectar rewards. For the entire sample, and for subsets excluding species in the Asteraceae and Orchidaceae, we found no significant difference among colour categories in the frequency of high nectar reward. This suggests that whilst such relationships between flower colour signals and nectar volume rewards have been observed at a field site in Germany, the effect is likely to be specific at a community level rather than a broad general principle that has resulted in the common signalling of bee flower colours around the world.

Floral recovery from accidents

Pollination Plants in the field layer may be susceptible to damage, with their stems bent or twisted by wind, falling objects, or trampling. For flowers specialized to attract insect pollinators, such accidents can cause changes in orientation that could decrease the chances of successful pollination. In experiments with a range of herbaceous species, Armbruster and Muchhala compared the postinjury responses of bilaterally symmetrical flowers with those of radially symmetrical flowers. Bilateral flowers mostly showed the ability to correct their position though reorientation of the floral stem or the floral sexual organs themselves, resulting in restoration of pollination efficiency. Few radially symmetrical flowers showed the same ability because their orientation had little effect on pollination accuracy. New Phytol. 10.1111/nph.16482 (2020).

Pollination Biology and Breeding System of Maple Species Acer oblongum Wall. ex DC. (Sapindaceae) Showing Mixed Syndromes of Wind and Insect Pollination

Acer oblongum is unique among maples because of the leaf structure and cryptic monoecy. In the present study, an in-depth investigation of reproductive biology has been carried out to study the pollination biology and breeding system of the tree species. The flowers show mixed characteristics of both entomophilous and anemophilous pollination in structure and pollen characteristics, respectively, and can thus be considered as ambophilous (exhibiting traits conducive to both insect and wind pollination). The wind was the primary means of pollination, but exclusion experiments showed that insects (Apis dorsata and syrphid fly) also facilitated pollination by 3–5%. The stigma of hermaphrodite flowers is located 2–3 cm above the level of indehiscent anthers. Interestingly, the insect pollinators hardly came in contact with the pistil; they only brought the pollen close to the stigma and shed it in its vicinity, to be trapped almost like the wind-borne pollen grains on the stigmatic papillae. Anthers of hermaphrodite flowers serve a relict function by attracting insect pollinators, but not contributing to self or cross-pollination. Fruit set following manual geitonogamous and xenogamous pollination showed a difference. The probable reason accounting for low fruit set seems to be the limited number of pollen donors (Staminate type II flowers), high pollen sterility, sparse distribution of individual trees, and geitonogamous pollen. Fruits are dry, indehiscent samaras. Mature fruits do not invariably bear seeds inside since hollow fruits are formed even when ovules inside remain unfertilized.

A key floral scent component (β‐trans‐bergamotene) drives pollinator preferences independently of pollen rewards in seep monkeyflower

AbstractFloral odours play an important role in attracting insect pollinators. Because pollinators visit flowers to obtain pollen and nectar rewards, they should prefer floral odour profiles associated with the highest‐rewarding flowers (honest signals). In previous work, bumblebees exhibited a preference for flowers from outbred over inbredMimulus guttatusplants. Pollen is the only floral reward inM. guttatus, and pollen viability (a reliable indicator of protein content) is reduced in inbred plants. Yet, differences in pollen viability did not explain the observed preferences.In this study, we examined the floral volatile profiles of inbred and outbredM. guttatusto identify inbreeding effects and associations between volatile compounds and the number of viable pollen grains per flower, designated “PRQ” (pollen reward quality). We also conducted pairwise choice tests withBombus impatiensto evaluate the ability of bees to discriminate between odours of rewarding and non‐rewarding flowers and to determine whether bumblebee preferences are explained by differences in the floral odours of inbred and outbred plants.Inbred plants exhibited reduced emission of β‐trans‐bergamotene, the second‐most abundant compound in the volatile blend of outbred plants. Furthermore, pollen and fertile anthers emitted nonadecane. Six other compounds in the floral blend were positively correlated withPRQ. There was no overlap between compounds affected by inbreeding and compounds associated withPRQ.Even when given prior experience foraging onM. guttatus, bumblebees did not distinguish between the floral odours of rewarding and non‐rewarding outbred plants. However, they preferred floral odours from non‐rewarding outbred plants over rewarding inbred plants. Bumblebees without prior experience of flowers preferred volatile blends with higher versus lower amounts of β‐trans‐bergamotene.Taken together, these results suggest that the volatile emissions ofM. guttatusprovide reliable indicators of pollen rewards (potential honest signals), but that the preference of bumblebees for outbred plants is not driven by these cues but rather by a sensory bias for β‐trans‐bergamotene. This may represent a subtle form of deceit‐pollination that allows plants to attract pollinators while minimizing investment in costly rewards.Aplain language summaryis available for this article.

Transcriptional regulation of anthocyanin biosynthesis in a high-anthocyanin resynthesized Brassica napus cultivar

BackgroundAnthocyanins are plant secondary metabolites with key roles in attracting insect pollinators and protecting against biotic and abiotic stresses. They have potential health-promoting effects as part of the human diet. Anthocyanin biosynthesis has been elucidated in many species, enabling the development of anthocyanin-enriched fruits, vegetables, and grains; however, few studies have investigated Brassica napus anthocyanin biosynthesis.ResultsWe developed a high-anthocyanin resynthesized B. napus line, Rs035, by crossing anthocyanin-rich B. rapa (A genome) and B. oleracea (C genome) lines, followed by chromosome doubling. We identified and characterized 73 and 58 anthocyanin biosynthesis genes in silico in the A and C genomes, respectively; these genes showed syntenic relationships with 41 genes in Arabidopsis thaliana and B. napus. Among the syntenic genes, twelve biosynthetic and six regulatory genes showed transgressively higher expression in Rs035, and eight structural genes and one regulatory gene showed additive expression. We identified three early-, four late-biosynthesis pathways, three transcriptional regulator genes, and one transporter as putative candidates enhancing anthocyanin accumulation in Rs035. Principal component analysis and Pearson’s correlation coefficients corroborated the contribution of these genes to anthocyanin accumulation.ConclusionsOur study lays the foundation for producing high-anthocyanin B. napus cultivars. The resynthesized lines and the differentially expressed genes we have identified could be used to transfer the anthocyanin traits to other commercial rapeseed lines using molecular and conventional breeding.

Flower age expressed in thermal time: is nectar secretion synchronous with pistil receptivity in oilseed rape (Brassica napus L.)?

Floral longevity can vary substantially with temperature in a given plant species. Thermal time has been widely used to measure developmental age of plants and poikilothermic organisms. We tested whether thermal time was suitable to express flower age to characterise the duration of pistil receptivity and that of nectar secretion in undisturbed flowers of oilseed rape (OSR), and whether these two functional processes were synchronous. Flower age was measured in a male fertile hybrid F1 line and in its male sterile (MS) parental line to determine if the presence of pollen affected the nectar secretion period. Hand pollinations and nectar samplings were conducted throughout the lifespan of OSR flowers on several flower cohorts from plants grown under tunnels under various temperature conditions. The number of seeds produced per flower was used as a proxy to assess the level of pistil receptivity at the time of hand-pollination. Thermal time was more suitable than calendar time to express OSR flower age. A phase of maturity followed by a phase of senescence took place in the two processes, and both proceeded faster as temperature increased. Nectar was secreted during the phase of full pistil receptivity, and, in the MS line, was then reabsorbed during the gradual decline of pistil receptivity. However, the nectar secretion period was extended beyond the onset of pistil senescence in the F1 line. OSR flowers invest in nectar secretion to attract insect pollinators at least to cover the whole receptivity period of their female part. Nectar secretion may be prolonged in pollen-laden male fertile flowers to attract insect pollinators longer to ensure as long as possible the probability of their pollen being disseminated. Flower senescence is triggered by pistil senescence, while the presence of pollen in anthers acts as an inhibitor and therefore delays flower senescence. Thermal time should henceforth be used to express more universally the age of plant organs and to model the duration of processes in relation to temperature, especially in the advent of global warming.

Взаємодія представників роду Buddleja L. з комахами-запилювачами

Наведено дані щодо особливостей запилення представників роду Buddleja L. На основі аналізу літературних даних описано концепції "синдрому запилення", що базуються на конкретних ознаках квіток: форма, колір, запах, розмір. Запропоновано дані концепції такими вченими, як: F. Delpino, S. Vogel в модифікації L. Van der Pijl та K. Faegri, W. N. Ellis, A. C. Ellis-Adam, H. Muller. Дослідження проведено зі січня по серпень 2011–2012 р. в китайсько-гімалайському регіоні Сичуань та Юньнань, адже саме цей регіон є частиною глобального осередку зростання великого різноманіття видів роду та вторинним центром походження азіатських видів. Для досліджень було обрано 5 видів роду Buddleja L.: B. asiatica Lour., B. crispa Benth., B. forrestii Diels, B. macrostachya Benth. та B. myriantha Diels. Описано зв'язок між морфологічною будовою квітки досліджуваних рослин та анатомічною будовою ротових апаратів запилювачів. Наведено склад ароматичних сполук квітів Buddleja L. З'ясовано, які комахи-запилювачі найчастіше відвідують досліджувані рослини. Основними запилювачами були бджоли, джмелі. Усі досліджувані види мають вузьку, довгу трубку віночка з прихованим нектаром. Із досліджень видно, що первинними запилювачами всіх видів роду є бджоли, а не метелики. Лише B. crispa Benth. приваблює метеликів. B. davidii Franche. запилюється переважно метеликами та міллю та дуже рідко бджолами. Також, на основі літературних джерел, було описано хімічний склад запаху квіток. На основі спостережень було виявлено, що найчастішими відвідувачами цих рослин як у Північній, так і в Південній Америці є медоносні бджоли, мухи, дзюрчалки, джмелі, оси та зрідка метелики, особливо головчаки. Охарактеризовано особливості кольорової гами квіток видів роду Buddleja L. З'ясовано вплив кількості нектару та його хімічний склад на приваблення запилювачів. Отже, існує чимало концепцій "синдрому запилення". Однією з найпопулярніших є типологія, яку запропонували W. N. Ellis, A. C. Ellis-Adam.

Comparative multi-omics analysis reveals diverse latex-based defense strategies against pests among latex-producing organs of the fig tree (Ficus carica).

Latexes in immature fruit, young petioles and lignified trunks of fig trees protect the plant using toxic proteins and metabolites in various organ-dependent ways. Latexes from plants contain high amounts of toxic proteins and metabolites, which attack microbes and herbivores after exudation at pest-induced wound sites. The protein and metabolite constituents of latexes are highly variable, depending on the plant species and organ. To determine the diversity of latex-based defense strategies in fig tree (Ficus carica) organs, we conducted comparative proteomic, transcriptomic and metabolomic analyses on latexes isolated from immature fruit, young petioles and lignified trunks of F. carica after constructing a unigene sequence library using RNA-seq data. Trypsin inhibitors were the most abundant proteins in petiole latex, while cysteine proteases ("ficins") were the most abundant in immature fruit and trunk latexes. Galloylglycerol, a possible defense-related metabolite, appeared to be highly accumulated in all three latexes. The expression levels of pathogenesis-related proteins were highest in the latex of trunk, suggesting that this latex had adapted a defensive role against microbe attacks. Although young petioles and immature fruit are both unlignified soft organs, and potential food for herbivorous insects, unigenes for the sesquiterpenoid pathway, which likely produces defense-associated volatiles, and the phenylpropanoid pathway, which produces toxic furanocoumarins, were expressed less in immature fruit latex. This difference may indicate that while petioles and fruit protect the plant from attack by herbivores, the fruit must also attract insect pollinators at younger stages and animals after ripening. We also suggest possible candidate transcription factors and signal transduction proteins that are involved in the differential expression of the unigenes.

Elucidating the substrate specificities of acyl-lipid thioesterases from diverse plant taxa

Acyl-ACP thioesterase enzymes, which cleave fatty acyl thioester bonds to release free fatty acids, contribute to much of the fatty acid diversity in plants. In Arabidopsis thaliana, a family of four single hot-dog fold domain, plastid-localized acyl-lipid thioesterases (AtALT1-4) generate medium-chain (C6-C14) fatty and β–keto fatty acids as secondary metabolites. These volatile products may serve to attract insect pollinators or deter predatory insects. Homologs of AtALT1-4 are present in all plant taxa, but are nearly all uncharacterized. Despite high sequence identity, AtALT1-4 generate different lipid products, suggesting that ALT homologs in other plants also have highly varied activities. We investigated the catalytic diversity of ALT-like thioesterases by screening the substrate specificities of 15 ALT homologs from monocots, eudicots, a lycophyte, a green microalga, and the ancient gymnosperm Gingko biloba, via expression in Escherichia coli. Overall, these enzymes had highly varied substrate preferences compared to one another and to AtALT1-4, and could be classified into four catalytic groups comprising members from diverse taxa. Group 1 ALTs primarily generated 14:1 β-keto fatty acids, Group 2 ALTs produced 6–10 carbon fatty/β-keto fatty acids, Group 3 ALTs predominantly produced 12–14 carbon fatty acids, and Group 4 ALTs mainly generated 16 carbon fatty acids. Enzymes in each group differed significantly in the quantities of lipids and types of minor products they generated in E. coli. Medium-chain fatty acids are used to manufacture insecticides, pharmaceuticals, and biofuels, and ALT-like proteins are ideal candidates for metabolic engineering to produce specific fatty acids in significant quantities.

Flower palate ultrastructure of the carnivorous plant Genlisea hispidula Stapf with remarks on the structure and function of the palate in the subgenus Genlisea (Lentibulariaceae)

In the genus Genlisea as well as in its sister genus Utricularia, the palate probably plays a key role in providing the colour, mechanical and olfactory stimuli to attract insect pollinators and to guide them to the generative structures and the nectary spur. However, information about the micro-morphology of the palate of Genlisea is scarce. This study aims to examine the structure of the palate in Genlisea hispidula in detail as well as the palate from other five species from the subgenus Genlisea. In particular, its aim is to ascertain whether these palates function as an area for the osmophores in the flower or whether they produce nectar. We showed that the palate in all of the species that were examined was the glandular type and that it had capitate, glandular trichomes, which had a similar general architecture across the species that were examined. No nectar secretion was observed on the palates. The ultrastructure of the palate trichomes showed that the palate glandular trichomes most probably function as scent glands that produce an olfactory stimulus for flower pollinators.

Temporal rhythm of petal programmed cell death in Ipomoea purpurea.

Flowers are the main sexual reproductive organs in plants. The shapes, colours and scents of corolla of plant flowers are involved in attracting insect pollinators and increasing reproductive success. The process of corolla senescence was investigated in Ipomoea purpurea (Convolvulaceae) in this study. In the research methods of plant anatomy, cytology, cell chemistry and molecular biology were used. The results showed that at the flowering stage cells already began to show distortion, chromatin condensation, mitochondrial membrane degradation and tonoplast dissolution and rupture. At this stage genomic DNA underwent massive but gradual random degradation. However, judging from the shape and structure, aging characteristics did not appear until the early flower senescence stage. The senescence process was slow, and it was completed at the late stage of flower senescence with a withering corolla. We may safely arrive at the conclusion that corolla senescence of I.purpurea was mediated by programmed cell death (PCD) that occurred at the flowering stage. The corolla senescence exhibited an obvious temporal rhythm, which demonstrated a high degree of coordination with pollination and fertilization.

Air pollutants degrade floral scents and increase insect foraging times

Flowers emit mixtures of scents that mediate plant-insect interactions such as attracting insect pollinators. Because of their volatile nature, however, floral scents readily react with ozone, nitrate radical, and hydroxyl radical. The result of such reactions is the degradation and the chemical modification of scent plumes downwind of floral sources. Large Eddy Simulations (LES) are developed to investigate dispersion and chemical degradation and modification of floral scents due to reactions with ozone, hydroxyl radical, and nitrate radical within the atmospheric surface layer. Impacts on foraging insects are investigated by utilizing a random walk model to simulate insect search behavior. Results indicate that even moderate air pollutant levels (e.g., ozone mixing ratios greater than 60 parts per billion on a per volume basis, ppbv) substantially degrade floral volatiles and alter the chemical composition of released floral scents. As a result, insect success rates of locating plumes of floral scents were reduced and foraging times increased in polluted air masses due to considerable degradation and changes in the composition of floral scents. Results also indicate that plant-pollinator interactions could be sensitive to changes in floral scent composition, especially if insects are unable to adapt to the modified scentscape. The increase in foraging time could have severe cascading and pernicious impacts on the fitness of foraging insects by reducing the time devoted to other necessary tasks.