The Production and Protection of Nectars

Escalante-Pérez, María; Heil, Martin

doi:10.1007/978-3-642-30967-0_9

Cited by 7 publications

(6 citation statements)

References 137 publications

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“…U๙der such co๙ditio๙s M. reukaufii usually reaches co๙siderably higher cell de๙sities tha๙ M. gruessii. Differe๙tial respo๙ses to toxic substa๙ces i๙ ๙ectar may also co๙tribute to growth differe๙ces betwee๙ yeast species, as they may act as barriers agai๙st yeast colo๙izatio๙ (Escala๙te-Pérez & Heil, 2013). The prese๙ce of protoa๙emo๙i๙, a๙ a๙tifu๙gal lacto๙e (Ca๙to A & Herrera CM u๙published results), i๙ H. foetidus ๙ectar might have i๙flue๙ced M. reukaufii a๙d M. gruessii differe๙tially, but this hypothesis remai๙s to be explored.…”

Section: Discussionmentioning

confidence: 99%

Comparative effects of two species of floricolous <em>Metschnikowia</em> yeasts on nectar

Canto¹,

Herrera²,

García³

et al. 2015

Anal. Jard. Bot. Madr.

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Canto, A., Herrera, C.M., García, I.M., García, M., Bazaga, P. 2015.Comparative effects of two species of floricolous Metschnikowia yeasts on nectar. Anales Jard. Bot. Madrid 72(1): e019Nectar yeast communities in southern Spain are dominated by two closely-related species, Metschnikowia reukaufii Pitt & M.W. Mill. and M. gruessii Gim.-Jurado (Ascomycota, Saccharomycetales), although they tend to be distributed differentially across different host plants. We explore here the possibility that the two yeasts play different functional roles in floral nectar by differing in their impact on sugar concentration and composition of nectar. Experiments were undertaken under controlled conditions using bumblebees caught foraging on the flowers of two different host plants each of which is known to harbor predominantly one of the two yeasts. Bumblebees were used as sources of inocula to obtain two groups of samples from the nectar of Helleborus foetidus L. (Ranunculaceae): nectar samples inoculated with M. gruessii and samples inoculated with M. reukaufii. Metschnikowia gruessii was poorly represented in nectar samples, while M. reukaufii was by far the most common and had the highest cell density. Although the two yeasts caused relatively similar changes in nectar sugar composition, which involved increasing fructose and decreasing sucrose proportions, they marginally differed in their quantitative impact on total nectar sugar concentration. Results suggest that differential yeast occurrence across host plants may lead to yeast specialization and modify the outcomes of the plant-pollinator interface. . Ambas levaduras son especies muy cercanas entre sí, pero se distribuyen diferencialmente entre las especies de plantas cuyo néctar las hospeda. En este trabajo se explora la posibilidad de que las levaduras tengan funciones distintas impactando diferencialmente la concentración y composición del néctar. Para esto se realizaron experimentos bajo condiciones controladas usando individuos de abejorros que fueron capturados cuando visitaban flores que albergan predominantemente una de las dos posibles levaduras mencionadas. Los abejorros fueron utilizados como agentes inoculantes naturales en el néctar de Helleborus foetidus L. para obtener dos grupos de muestras, unas con M. reukaufii y otras con M. gruessii. Los resultados mostraron que M. gruessii estuvo pobremente representada en las muestras; en contraste, M. reukaufii fue la más frecuente y de mayor densidad en el néctar. Aun cuando ambas levaduras tuvieron un efecto similar en la composición proporcional de los azúcares en el néctar, aumento de la fructosa y decremento de la sacarosa, las dos especies difieren marginalmente en su impacto en la concentración total de azúcares. Los resultados sugieren que la ocurrencia diferencial de las especies de levaduras entre sus plantas hospederas, puede conducir a una modificación en las interacciones entre las plantas y sus visitantes florales y también a una especialización de levaduras por hospedero.

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Section: Discussionmentioning

confidence: 99%

Comparative effects of two species of floricolous <em>Metschnikowia</em> yeasts on nectar

Canto¹,

Herrera²,

García³

et al. 2015

Anal. Jard. Bot. Madr.

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“…Visiting insects are not sterile, and can transfer microbes between flowers (Ferrari et al . ; Escalante‐Perez & Heil ) and, because many flowers remain open for several days, there is in theory that this allows ample time for microbes there to multiply, using nectar as a growth medium. Nevertheless, infections of the gynoecium are in fact relatively rare in plants, implying the presence of an active defence system in nectar to reduce such infections (Thornburg et al .…”

Section: Introductionmentioning

confidence: 99%

Floral nectar of the obligate outcrossing Canavalia gladiata (Jacq.) DC. (Fabaceae) contains only one predominant protein, a class III acidic chitinase

Milne

Zhou

et al. 2017

Plant Biol J

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Floral nectar can affect the fitness of insect-pollinated plants, through both attraction and manipulation of pollinators. Self-incompatible insect-pollinated plants receive more insect visits than their self-compatible relatives, and the nectar of such species might face increased risk of infestation by pathogens carried by pollinators than self-compatible plants. Proteins in nectar (nectarins) play an important role in protecting the nectar, but little is known regarding nectarins in self-incompatible species. The nectarins from a self-incompatible and insect-pollinated leguminous crop, Canavalia gladiata, were separated using two-dimensional electrophoresis and analysed using mass spectrometry. The predominant nectarin gene was cloned and the gene expression pattern investigated using quantitative real-time PCR. Chitinolytic activity in the nectar was tested with different substrates. The C. gladiata nectar proteome only has one predominant nectarin, an acidic class III chitinase (CaChi3). The full-length CaChi3 gene was cloned, coding for a protein of 298 amino acids with a predicted signal peptide. CaChi3 is very similar to members of the class III chitinase family, whose evolution is dominated by purifying selection. CaChi3 was expressed in both nectary and leaves. CaChi3 has thermostable chitinolytic activity according to glycol-chitin zymography or a fluorogenic substratem but has no lysozyme activity. Chitinase might be a critical protein component in nectar. The extremely simple nectar proteome in C. gladiata disproves the hypothesis that self-incompatible species always have more complex nectar proteomes. Accessibility of nectar might be a significant determinant of the evolutionary pressure to develop nectar defence mechanisms.

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“…Another aspect of nectar secretion is the expression of a redox cycle in the nectar, which is thought to produce reactive oxygen species (ROS) for protection of the sugar‐rich nectar from contamination with and growth of microorganisms, i.e. bacteria and especially yeasts (Carter & Thornburg, 2004a; Escalante‐Pérez & Heil, ). Nectar may contain high levels of hydrogen peroxide (H 2 O 2 ) (Carter & Thornburg, 2000; 2004a, b).…”

Section: Introductionmentioning

confidence: 99%

“…Ascorbate in the nectar serves as an extracellular antioxidant (Carter & Thornburg, 2004a, b; Horner et al ., ). A manganese superoxide dismutase (Mn‐SOD) named ‘nectarin’ and a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase are involved in the nectar–redox cycle (Carter & Thornburg, , 2004a; Carter et al ., ; Escalante‐Pérez & Heil, ). However, while the molecular basis and enzymology of the nectar–redox cycle are well studied (references above), there appears to be no information about the origin of the reduction equivalents ([2H]) required for the redox turnover of the nectar–redox cycle.…”

Section: Introductionmentioning

confidence: 99%

Green nectaries: the role of photosynthesis in secretion

Lüttge

2013

Bot J Linn Soc

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Green nectaries have been frequently mentioned in the literature, leading to the assumption that photosynthesis of nectaries can supply the carbohydrates secreted in the nectar, especially when storage of starch is seen in the plastids in nectaries and this starch disappears during secretion. Photosynthesis in nectaries can also provide reduction equivalents for the nectar-redox cycle and energy for secretion. However, quantitative data on the photosynthetic capacity of nectaries are largely missing. Therefore, in the present study, the photosynthetic capacity of green nectaries from a range of plants was screened; 20 floral nectaries (including six septal nectaries) and six extrafloral nectaries were studied. For the screening, chlorophyll fluorescence parameters were measured as depending on photosynthetic photon flux density (PPFD). Parameters measured were basic ground fluorescence (F) and quantum yield (Y0) of the dark adapted sample at 0 PPFD. From the light saturation curves saturating PPFD (PPFDsat), quantum yield at saturation (Ysat) and maximum apparent photosynthetic electron transport rates (ETRmax) were obtained. For comparison, leaves of the plants were also measured. In most cases, the performance of the nectaries was lower than that of the leaves. F was lower in 14 floral and four extrafloral nectaries (69% of total), ETRmax was lower in 18 floral and four extrafloral nectaries (85%), Ysat was lower in 15 floral and three extrafloral nectaries (69%). In 18 floral and two extrafloral nectaries (77%) Y0 was well below 0.8, indicating photoinhibition. In contrast, the range of ETRmax for green nectaries was 25-140 μmol m −2 s −1 and overlaps well with that of green tissues in general. The lower end of the range of rates of photosynthetic carbon dioxide (CO2) uptake of sun leaves in the literature is 10 μmol CO2 m −2 s −1 . Taking this value for sun-adapted green nectaries, i.e. having a PPFDsat > 1000 μmol m −2 s −1 , with an area of nectar tissue measured as 3-50 mm 2 per flower, sugar secretion related to photosynthetic CO2 fixation in the green nectaries is estimated at approximately 0.2-3.0 μmol hexose units flower −1 day −1 . This is compares well in order of magnitude with the range of secretion given in the literature and clearly suggests that photosynthetic activity of green nectaries can explain a significant part, if not all, of the sugar secreted. In some nectaries ETR did not saturate with PPFD. This could be attributable to spillover from photosystem II to photosystem I and cyclic photosynthetic electron transport. It is in agreement with observations in the literature and my preliminary findings that nectary plastids often lack grana thylakoids where photosytem II is located. Cyclic photophosphorylation could provide adenosine triphosphate (ATP) energy for the nectaries. This needs further investigation.

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The Production and Protection of Nectars

Cited by 7 publications

References 137 publications

Comparative effects of two species of floricolous <em>Metschnikowia</em> yeasts on nectar

Comparative effects of two species of floricolous <em>Metschnikowia</em> yeasts on nectar

Floral nectar of the obligate outcrossing Canavalia gladiata (Jacq.) DC. (Fabaceae) contains only one predominant protein, a class III acidic chitinase

Green nectaries: the role of photosynthesis in secretion

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