Transcriptome analysis of the influence of CPPU application for fruit setting on melon volatile content

In fruit production,the application of the plant growth regulator 1-(2-chloro-4-pyridyl)-3-phenylurea(CPPU)dulls the fruit aroma.Gas chromatography-mass spectrometry and transcriptome analyses were performed on CPPU-treated and pollinated fruits to determine how CPPU affects the production of aroma in melon fruit.The results showed that the contents of two important esters(benzyl acetate and phenethyl acetate)in the CPPU-treated fruits were significantly lower than those in the pollinated fruits.Transcriptome sequencing data revealed that most differentially expressed genes were involved in“phenylalanine metabolism”pathway,and their expression was significantly decreased in the CPPU-treated fruits.Further analysis showed that the phenylalanine content in the CPPU-treated fruits was significantly higher than that in the pollinated fruits.In summary,CPPU application interferes with phenylalanine metabolism in melon fruits and affects the production of aromatic esters.

Floral traits and pollination system of Zygophyllum xanthoxylum in the managed and wild populations in an arid region of Northwest China

Zygophyllum xanthoxylum, which belongs to Sarcozygium of Zygophyllaceae, is one of the ecologically important species in Northwest China. In order to understand the pollination system of Z. xanthoxylum, we investigated the following characteristics of this species in the Urat Desert-grassland Research Station in western Inner Mongolia of China： flowering dynamics, pollen viability, pollen limitation, floral visitors and breeding system. The results showed that the flowering period and flowering peak were different between the wild and managed popula- tions, being longer in the managed population. Z. xanthoxylum was pollen-limited, and pollen limitation was more intense in the wild population than in the managed population. Chalicodoma deserticola （Hymenoptera） was found to be the most frequent pollinator in the wild population, while Anthophora fulvitarsis （Hymenoptera） was the most frequent and effective visitor in the managed population. Out-crossing was dominant in the breeding system and self-pollination just played an assistant role to assure the reproduction of Z. xanthoxylum.

Reproduction of Hedysarum scoparium (Fabaceae) in patched habitat is pollen limited,but not just pollinator limited

Pollen limitation of plant reproduction occurs across Angiosperms, particularly those in patched habitats We investigated the, relationship between pollen limitation and patch variables （patch size, visitation frequency） in the desert plant Hedysarum scoparium （Fabaceae）, which is an important xerophyte in the arid and semi-arid regions of Northwest China and can grow well as a pioneer plant in shifting sand dunes. We observed insect visitation to H. scoparium over two flowering seasons and estimated pollen limitation using fruit set and seed production. Our results indicate that fruit set and seed production increased significantly with pollen supplementation compared with open pollination. Hedysarum scoparium was pollinated by over 8 species of bees, with 88.4% of visits made by introduced honeybees （Apis mellifera）. Bee visitation varied significantly among the patches of habitats, but not associated with patch size of habitat. In general, pollen limitation occurred more strongly during fruit set than during seed production. The patches that received higher rates of pollinator visits were less pollen limited for fruit set. Pollen limitation for seed production, however, was not associated with pollinator visitation frequency. We conclude that pollen limitation in H. scoparium was caused by more than one reason, not just pollinator visits.

Seasonal change mediates the shift between resource and pollen limitation in Hedysarum scoparium(Fabaceae)

Theory suggests that with sufficient environmental variation, pollen limitation might be observed at some places or times, and resource limitation at others, but there are no empirical data about the effect of seasonal change on the variation of pollen limitation and resource limitation within a flowering season. In this study, we examined pollen and resource limi- tation by comparing fruit set and seed production in natural- and hand-pollinated Hedysarum scoparium flowers in the middle reaches of the Hexi Corridor region, China, in 2010. We also described a role for the first substantial autumn rainfall in mediating a shift between pollen and resource limitation in H. scoparium, but did not analyze this experimentally Our results indicated that H. scoparium was resource limited at peak flowering during the summer, and was pollen limited at peak flowering during the autumn. The seasonal change （summer to autumn） mediated the shift between pollen and resource limitations in H. scoparium. The shift timing depended on the date of the first autumn rainfall in 2010. Changes in the first substantial rainfall in autumn may affect fruiting of H. scoparium, thus affecting population persistence of this species and development/structure of the local ecosystem if such conditions persist.

Influences of Cross Pollination on Pollen Tube Growth and Fruit Set in Zuili Plums (Prunus salicina)

Zuili plum （Prunus salicina L.） trees usually set fruit poorly, although they produce high quality fruit. To elucidate the causes of the poor fruit set, pollen tube growth into pistils and fruit set percentage were investigated after cross-, self- and open-pollination. Ovule development in Zuili pistils was also investigated. Pollen tube penetration into the ovules via the obturator and micropyle was best when Zuili pistils were pollinated by cv. Black Amber （P. domestica） pollen grains, although cross-pollinations with Hongxinli and Miili （P. salicina） pollen were more effective than self- and open-pollination. The fruit set percentage was also highest in pistils pollinated with Black Amber pollen grains. Morphological observation of Zuili pistils revealed that the trees produce ＂double pistils＂, developing two ovaries from a basal pistil, at a rate as high as 28%. In such abnormal pistils, most ovules were lacking an embryo sac or were entirely degenerated. The percentage of normally developed ovules was 24.3% and 8.9% in normal and double pistils, respectively. From these results, we conclude that the main causes of poor fruit set of Zuili plums are a lack of effective cross-pollination and the production of high percentages of double pistils in which normally developed ovules are scarcely formed.

Tomato Ovary-to-Fruit Transition is Characterized by a Spatial Shift of mRNAs for Cell Wall Invertase and its Inhibitor with the Encoded Proteins Localized to Sieve Elements

Central to understanding fruit development is to elucidate the processes mediating a successful transition from pre-pollination ovaries to newly set fruit, a key step in establishing fruit yield potential. In tomato, cell wall invertase （CWIN） LIN5 and its inhibitor INH1 are essential for fruit growth. However, the molecular and cellular basis by which they exert their roles in ovary-to-fruit transition remains unknown. To address this issue, we conducted a study focusing on ovaries and fruitlets at 2 days before and 2 days after anthesis, respectively. In situ hybridization analyses revealed that LIN5 and INH1 exhibited a dispersed expression in ovaries compared with their phloem-specific expression in fruitlets. Remarkably, LIN5 and INH1 proteins were immunologically co-localized to cell walls of sieve elements （SEs） in ovaries immediately prior to anthesis and in young fruitlets, but were undetectable in provascular bundles of younger ovaries. A burst in CWlN activity occurred during ovary-to-fruit transition. Interestingly, the ovaries, but not the fruit- lets, exhibited high expression of a defective invertase, SldeCWIN1, an ortholog of which is known to enhance inhibition of INH on CWlN activity in tobacco. Imaging of a fluorescent symplasmic tracer indicated an apoplasmic phloem unloading pathway operated in ovaries, contrary to the previously observed symplasmic unloading pathway in fruit pericarp. These new data indicate that （1） a phloem-specific patterning of the CWIN and INH mRNAs is induced during ovary-to-fruit transition, and （2） LIN5 protein functions specifically in walls of SEs and increases its activity during ovary-to-fruit transition, probably to facilitate phloem unloading and to generate a glucose signal positively regulating cell division, hence fruit set.

Floral resources, pollinators and fruiting in a threatened tropical deciduous tree

Nothapodytes nimmoniana(Family Icacinaceae)is a deciduous tree species distributed in Asia facing severe population decline.Wood chips from the tree are a source of camptothecin,a globally soughtafter alkaloid with cancer-treating properties,and are harvested unsustainably in natural forests.We studied the pollination ecology of the species and asked if there are constraints in pollination and fruiting success in its natural populations.We also discuss the potential effects of wood extraction on pollinators and reproductive success in the population.Methods The study was carried out during the flowering season in two populations with varying exploitation levels,both located in the Protected Area Network in the Western Ghats of Karnataka State.We assessed floral resource availability and measured pollinator diversity and activity in the canopy from the perspective of the biology of the species.We quantified pollinator abundance and percent fruit set as a function of population density.Important Findings Flowers belong to the fly pollination syndrome and are open to visits by generalists such as Apis dorsata and Trigona iridipennis.Fruiting success did not vary between exploited and unexploited sites,but there was a significant difference in pollinator assemblage.In a lean male flowering year,fruit set was low,suggesting pollen limitation in the population.No fruiting was recorded in the second year at the site where trees were felled soon after the flowering period.We argue that when male floral resources are altered in exploited populations,pollinators of generalist nature may show a shift in foraging pattern.Also,generalist plants may be as susceptible to pollination loss as are specialist plants.The need for outcrossing in the species would probably exacerbate this vulnerability.

Sugar Input, Metabolism, and Signaling Mediated by Invertase： Roles in Development, Yield Potential, and Response to Drought and Heat

Invertase （INV） hydrolyzes sucrose into glucose and fructose, thereby playing key roles in primary metabolism and plant development. Based on their pH optima and sub-cellular locations, INVs are categorized into cell wall, cytoplasmic, and vacuolar subgroups, abbreviated as CWlN, CIN, and VlN, respectively. The broad importance and implications of INVs in plant development and crop productivity have attracted enormous interest to examine INV function and regulation from multiple perspectives. Here, we review some exciting advances in this area over the last two decades, focusing on （1） new or emerging roles of INV in plant development and regulation at the post-translational level through interaction with inhibitors, （2） cross-talk between INV-mediated sugar signaling and hormonal control of development, and （3） sugar- and INV-mediated responses to drought and heat stresses and their impact on seed and fruit set. Finally, we discuss major questions arising from this new progress and outline future directions for unraveling mechanisms underlying INV-mediated plant development and their potential applications in plant biotechnology and agriculture.

Indirect costs counteract the effects of pollinator-mediated phenotypic selection on corolla size in the mediterranean shrub Halimium atriplicifolium

Aims larger corollas receive more pollinator visits but involve higher production and maintenance costs,especially under hot and dry conditions.this can result in indirect costs on reproductive output,which may counteract the effects of pollinator-mediated phenotypic selection on corolla size.In this study,I explored the relationship between corolla size and indirect costs and whether these costs counteract the effects of pollinator-mediated phenotypic selection on this trait in the mediterranean shrub Halimium atriplicifolium.I hypothesized that(i)corolla production entails direct costs in dry mass,N and P,(ii)corollas entail significant indirect costs in terms of fruit and seed production,(iii)indirect costs increase with corolla size,(iv)this species may suffer pollen limitation to a certain degree and(v)indirect costs counteract the effects of pollinator-mediated selection on corolla size.Methods I compared fruit set and seed production of petal-removed flow-ers(r flowers)and unmanipulated control flowers(C flowers)and evaluated the influence of individual mean corolla size on relative fruit and seed gain of r compared to C flowers.I also estimated phenotypic selection on corolla size mediated by indirect costs and the combined effect of costs and pollinators(i.e.total selection).Important Findings Corollas allocated sizeable amount of resources in terms of dry mass relative to the other floral structures.Fruit set and seed per fruit were significantly higher in r flowers,while individual mean corolla size showed a positive relationship with relative fruit gain.Phenotypic selection analysis revealed cost-mediated negative directional selection and absence of positive directional total selection on corolla size through fruit set.this translated into stabilizing total selection.these results suggest that mediterranean environments can impose constraints on corolla size,counteracting advantages of larger corollas from the pollination point of view with increased indirect costs of such flowers.

Insect pollinator dependence of shea (Vitellaria paradoxa C.F. Gaertn.) in the Guinea Savanna zone of Ghana

Shea(Vitellaria paradoxa C.F.Gaertn.)is a multipurpose tree species indigenous to the Sudano Sahelian zone of Africa and occurs as the most abundant economic tree species in northern Ghana.The edible oil(shea butter)extracted from shea kernel is ranked as the most economic product of the species.Although fruit set and yield of shea are known to be influenced by insect pollination,the actual contribution of insect pollinators to its reproductive success has rarely been studied.This study estimated the percentage insect pollinator dependence and monetary value of insect pollination per bag of shea kernel(85 kg)in the Guinea savanna zone.Open pollination and insect exclusion treatments were applied to the flowers of 18 randomly selected matured shea trees and observed from the onset of flowering to fruit maturity.Proportion of total production value attributed to insect pollination approach was used in estimating the monetary value of pollination per bag of shea kernel with the average market price as proxy.The study revealed an insect pollinator dependence of 77%and 73%for fruit set and dry kernel yield,respectively.Mean number of fruit set per inflorescence varied significantly between insectexcluded and open-pollinated inflorescences(p<0.05).The monetary value of insect pollination was estimated at GH₵73.21(US$18.67)per bag of kernel as of August 2016.Shea is a high insect pollinator–dependent species and the conservation of insect pollinators would be critical to the sustainability of yield.

Altitudinal variation in the reproductive performance of the Mediterranean shrub Rhamnus lycioides L.

Aims Rhamnus lycioides L.subsp.Oleoides(Rhamnaceae)is a perennial shrub native to the Mediterranean Basin distributed along an altitudinal gradient,from sea level up to 1000 m a.s.l.The specific goals of our study were(i)to compare plant morphology between two contrasting populations,(ii)to determine the reproductive system of R.lycioides,quantifying the relative importance of insects and wind as pollen vectors,(iii)to test if pollen limitation differs between populations,(iv)to study the main factors influencing fruit set and(v)to compare plant reproductive performance(mass allocation to flowers,fruits and seeds)between the two habitats.Methods In the present study,we examined plant morphology and the reproductive performance of R.lycioides L.in contrasting environments in two populations located at the extremes of its altitudinal range in the island of Mallorca(Balearic Islands,Western Mediterranean Basin)along a 3-year period.Plant morphology,the relative importance of insects and wind as pollen vectors,the pollen limitation to seed production and the plant reproductive performance(mass allocation to flowers,fruits and seeds)were determined.Important Findings Rhamnus lycioides individuals showed a higher plant surface/plant height ratio at the mountain than at the coast.This species appeared to be ambophilous despite its inconspicuous flowers,although the relative importance of wind as a pollination vector was higher at the mountain than at the coastal site.Fruit set was much higher at the mountain,where pollen appeared to be a limiting factor.By contrast,fruit set was not limited by pollen availability at the coastal population,where resource(water and nutrients)limitation seemed to be more determining.Flower size was greater at the coast,in contrast to fresh fruit weight that was higher at the mountain.Despite the relatively few differences between sites in precipitation patterns along the study period,water availability appeared to be the key factor explaining not only fruit set but also the reproductive performance of this species in the study populations.