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The Plant Journal : For Cell and... Oct 2021Reduction of crop yield due to iron (Fe) deficiency has always been a concern in agriculture. How Fe insufficiency in floral buds affects pollen development remains...
Reduction of crop yield due to iron (Fe) deficiency has always been a concern in agriculture. How Fe insufficiency in floral buds affects pollen development remains unexplored. Here, plants transferred to Fe-deficient medium at the reproductive stage had reduced floral Fe content and viable pollen and showed a defective pollen outer wall, all restored by supplying floral buds with Fe. A comparison of differentially expressed genes (DEGs) in Fe-deficient leaves, roots, and anthers suggested that changes in several cellular processes were unique to anthers, including increased lipid degradation. Co-expression analysis revealed that ABORTED MICROSPORES (AMS), DEFECTIVE IN TAPETAL DEVELOPMENT AND FUNCTION1, and BASIC HELIX-LOOP-HELIX 089/091/010 encode key upstream transcription factors of Fe deficiency-responsive DEGs involved in tapetum function and development, including tapetal ROS homeostasis, programmed cell death, and pollen outer wall formation-related lipid metabolism. Analysis of RESPIRATORY-BURST OXIDASE HOMOLOG E (RBOHE) gain- and loss-of-function under Fe deficiency indicated that RBOHE- and Fe-dependent regulation cooperatively control anther reactive oxygen species levels and pollen development. Since DEGs in Fe-deficient anthers were not significantly enriched in genes related to mitochondrial function, the changes in mitochondrial status under Fe deficiency, including respiration activity, density, and morphology, were probably because the Fe amount was insufficient to maintain proper mitochondrial protein function in anthers. To sum up, Fe deficiency in anthers may affect Fe-dependent protein function and impact upstream transcription factors and their downstream genes, resulting in extensively impaired tapetum function and pollen development.
Topics: Arabidopsis; Flowers; Gene Expression Regulation, Developmental; Gene Expression Regulation, Plant; Homeostasis; Iron; Iron Deficiencies; Lipid Metabolism; Mitochondria; Phenotype; Pollen; Reactive Oxygen Species; Transcriptome
PubMed: 34310779
DOI: 10.1111/tpj.15438 -
Scientific Data Oct 2023Pollen-based evidence of human presence is crucial for reconstructing human history. However, information on the morphology of pollen grains of global food plants and...
Pollen-based evidence of human presence is crucial for reconstructing human history. However, information on the morphology of pollen grains of global food plants and regional pollen-based human indicators is scattered in the literature, leading to the risk of overlooking important evidence of human presence. To address this issue, we first compiled a comprehensive overview of 354 major food plants worldwide, creating a paleoecology-friendly format that includes their family, vernacular name, earliest known use, environmental preference, and geographical region. Moreover, we identified the sources of illustrations of their pollen grains for 209 out of 273 different genera of globally relevant food plants in 10 selected pollen atlases. Secondly, we compiled all human indicators from pollen-based paleoecological literature in Latin America (based on 750 references), providing an overview of 212 single-pollen type indicators and identified 95 crucial combinations of pollen types as "human indices", and their corresponding references. Our review datasets aids in distilling human evidence from numerous fossil pollen records worldwide.
Topics: Humans; Fossils; Latin America; Plants, Edible; Pollen
PubMed: 37857627
DOI: 10.1038/s41597-023-02613-1 -
American Journal of Botany Jun 2023Linum suffruticosum shows variations in pollinator fit, pollen pickup, and local pollinators that predict pollen deposition rates. The species often coflowers with other...
PREMISE
Linum suffruticosum shows variations in pollinator fit, pollen pickup, and local pollinators that predict pollen deposition rates. The species often coflowers with other Linum species using the same pollinators. We investigated whether L. suffruticosum trait variation could be explained by local patterns of pollinator sharing and associated evolution to reduce interspecific pollen transfer.
METHODS
Pollinator observations were made in different localities (single species, coflowering with other congeners). Floral traits were measured to detect differences across populations and from coflowering species. Reproductive costs were quantified using interspecific hand pollinations and measures of pollen-tube formation, combined with observations of pollen arrival on stigmas and pollen-tube formation after natural pollination in allopatric and sympatric localities.
RESULTS
The size and identity of the most important pollinator of L. suffruticosum and whether there was pollinator sharing with coflowering species appeared to explain floral trait variation related to pollinator fit. The morphological overlap of the flowers of L. suffruticosum with those of coflowering species varied, depending on coflowering species identity. A post-pollination incompatibility system maintains reproductive isolation, but conspecific pollen-tube formation was lower after heterospecific pollination. Under natural pollination at sites of coflowering with congeners, conspecific pollen-tube formation was lower than at single-species localities.
CONCLUSIONS
Trait variation in L. suffruticosum appears to respond to the most important local pollinator. Locally, incomplete pollinator partitioning might cause interspecific pollination, imposing reproductive costs. These reproductive costs may generate selection on floral traits for reduced morphological overlap with coflowering congeners, leading to the evolution of pollination ecotypes.
Topics: Flax; Pollination; Reproduction; Flowers; Pollen
PubMed: 37163619
DOI: 10.1002/ajb2.16181 -
American Journal of Botany Jun 2023Deceptive pollination, a fascinating mechanism that independently originated in several plant families for benefiting from pollinators without providing any reward, is...
PREMISE
Deceptive pollination, a fascinating mechanism that independently originated in several plant families for benefiting from pollinators without providing any reward, is particularly widespread among orchids. Pollination efficiency is crucial in orchids due to the aggregated pollen in a pollinarium, which facilitates pollen transfer and promotes cross-pollination as pollinators leave after being deceived.
METHODS
In this study, we compiled data on reproductive ecology from five orchid species with different pollination strategies: three deceptive-strategy species (shelter imitation, food deception, sexual deception), one nectar-rewarding species, and one shelter-imitation but spontaneously selfing species. We aimed to compare the reproductive success (female fitness: fruit set; male fitness: pollinarium removal) and pollination efficiency of species representing these strategies. We also investigated pollen limitation and inbreeding depression among the pollination strategies.
RESULTS
Male and female fitness were strongly correlated in all species but the spontaneously selfing species, which had high fruit set and low pollinarium removal. As expected, pollination efficiency was highest for the rewarding species and the sexually deceptive species. Rewarding species had no pollen limitation but did have high cumulative inbreeding depression; deceptive species had high pollen limitation and moderate inbreeding depression; and spontaneously selfing species did not have pollen limitation or inbreeding depression.
CONCLUSIONS
Pollinator response to deception is critical to maintain reproductive success and avoid inbreeding in orchid species with non-rewarding pollination strategies. Our findings contribute to a better understanding of the trade-offs associated with different pollination strategies in orchids and highlight the importance of pollination efficiency in orchids due to the pollinarium.
Topics: Pollination; Orchidaceae; Reproduction; Pollen; Plant Nectar; Flowers
PubMed: 37342959
DOI: 10.1002/ajb2.16198 -
Current Biology : CB Apr 2019Many bees are effective pollen collectors; however, pollen grains collected by bees for larval food are lost for plant sexual reproduction. Recognition of these...
Many bees are effective pollen collectors; however, pollen grains collected by bees for larval food are lost for plant sexual reproduction. Recognition of these conflicting interests between bees and flowers is essential for understanding of reproduction for both bees and flowers [1-3]. Plant defense compounds in pollen may function to reduce pollen waste by deterring ineffective pollinators [4-6], but this hypothesis remains unexamined. Here, we provide evidence that secondary metabolites in pollen function as chemical defense by deterring some bees from gathering pollen. In two Dipsacus species, a defense compound, dipsacus saponin [7], occurs in pollen but not in nectar. We observed that bumblebees disliked grooming bitter-tasting pollen with a high saponin content. Manipulation of saponin concentrations in nectar and measurements of corbicular pollen showed that the bumblebee species differed in their tolerance to saponin. Those species susceptible to saponin groomed little Dipsacus pollen into their pollen loads, and their ungroomed pollen was observed to be effectively delivered to stigmas. By rewarding bees with edible nectar, but not pollen, plants solve the conflict of pollen partitioning between sexual and reward functions. Ungroomed toxic pollen on the bee body promotes pollen transfer efficiency, facilitating pollination.
Topics: Animals; Bees; Dipsacaceae; Plant Nectar; Pollen; Pollination; Saponins
PubMed: 30982649
DOI: 10.1016/j.cub.2019.03.023 -
Trends in Plant Science May 2017Pollinator behaviour has profound effects on plant mating. Pollinators are predicted to minimise energetic costs during foraging bouts by moving between nearby flowers.... (Review)
Review
Pollinator behaviour has profound effects on plant mating. Pollinators are predicted to minimise energetic costs during foraging bouts by moving between nearby flowers. However, a review of plant mating system studies reveals a mismatch between behavioural predictions and pollen-mediated gene dispersal in bird-pollinated plants. Paternal diversity of these plants is twice that of plants pollinated solely by insects. Comparison with the behaviour of other pollinator groups suggests that birds promote pollen dispersal through a combination of high mobility, limited grooming, and intra- and interspecies aggression. Future opportunities to test these predictions include seed paternity assignment following pollinator exclusion experiments, single pollen grain genotyping, new tracking technologies for small pollinators, and motion-triggered cameras and ethological experimentation for quantifying pollinator behaviour.
Topics: Animals; Birds; Pollen; Pollination; Reproduction
PubMed: 28412035
DOI: 10.1016/j.tplants.2017.03.005 -
The New Phytologist Feb 2020Pollen plays two important roles in angiosperm reproduction, serving as a vehicle for the plant's male gametes, but also, in many species, as a lure for pollen-feeding...
Pollen plays two important roles in angiosperm reproduction, serving as a vehicle for the plant's male gametes, but also, in many species, as a lure for pollen-feeding animals. Despite being an important food source for many pollinators, pollen often contains compounds with known deterrent or toxic properties, as documented in a growing number of studies. Here we review these studies and discuss the role of pollen defensive compounds in the coevolutionary relationship between plants and bees, the preeminent consumers of pollen. Next, we evaluate three hypotheses that may explain the existence of defensive compounds in pollen. The pleiotropy hypothesis, which proposes that defensive compounds in pollen merely reflect physiological spillover from other plant tissues, is contradicted by evidence from several species. Although plants may experience selection to defend pollen against poor-quality pollinators, we also find only partial support for the protection-against-pollen-collection-hypothesis. Finally, pollen defences might protect pollen from colonisation by antagonistic microorganisms (antimicrobial hypothesis), although data to evaluate this idea are scarce. Further research on the effects of pollen defensive compounds on pollinators, pollen thieves, and pollen-colonising microbes will be needed to understand why many plants have chemically defended pollen, and the consequences of those defences for pollen consumers.
Topics: Animals; Anti-Infective Agents; Bees; Biological Evolution; Ecological and Environmental Phenomena; Models, Biological; Pollen
PubMed: 31569278
DOI: 10.1111/nph.16230 -
Plant Reproduction Jun 2016Pollen heat acclimation. As a consequence of global warming, plants have to face more severe and more frequently occurring periods of high temperature stress. While this... (Review)
Review
Pollen heat acclimation. As a consequence of global warming, plants have to face more severe and more frequently occurring periods of high temperature stress. While this affects the whole plant, development of the male gametophyte, the pollen, seems to be the most sensitive process. Given the great importance of functioning pollen for the plant life cycle and for agricultural production, it is necessary to understand this sensitivity. While changes in temperature affect different components of all cells and require a cellular response and acclimation, high temperature effects and responses in developing pollen are distinct from vegetative tissues at several points. This could be related to specific physiological characteristics of developing pollen and supporting tissues which make them vulnerable to high temperature, or its derived effects such as ROS accumulation and carbohydrate starvation. But also expression of heat stress-responsive genes shows unique patterns in developing pollen when compared to vegetative tissues that might explain the failure to withstand high temperatures. As an alternative to viewing pollen failure under high temperature as a result of inherent sensitivity of a specific developmental process, we end by discussing whether it might actually be an adaptation.
Topics: Acclimatization; Climate Change; Heat-Shock Response; Hot Temperature; Pollen
PubMed: 27067439
DOI: 10.1007/s00497-016-0282-x -
Plant, Cell & Environment Mar 2021Research concerning the effects of ionizing radiation (IR) on plant systems is essential for numerous aspects of human society, as for instance, in terms of agriculture... (Comparative Study)
Comparative Study Review
Research concerning the effects of ionizing radiation (IR) on plant systems is essential for numerous aspects of human society, as for instance, in terms of agriculture and plant breeding, but additionally for elucidating consequences of radioactive contamination of the ecosphere. This comprehensive survey analyses effects of x- and γ-irradiation on male gametophytes comprising primarily in vitro but also in vivo data of diverse plant species. The IR-dose range for pollen performance was compiled and 50% inhibition doses (ID ) for germination and tube growth were comparatively related to physiological characteristics of the microgametophyte. Factors influencing IR-susceptibility of mature pollen and polarized tube growth were evaluated, such as dose-rate, environmental conditions, or species-related variations. In addition, all available reports suggesting bio-positive IR-effects particularly on pollen performance were examined. Most importantly, for the first time influences of IR specifically on diverse phylogenetic models of polar cell growth were comparatively analysed, and thus demonstrated that the gametophytic system of pollen is extremely resistant to IR, more than plant sporophytes and especially much more than comparable animal cells. Beyond that, this study develops hypotheses regarding a molecular basis for the extreme IR-resistance of the plant microgametophyte and highlights its unique rank among organismal systems.
Topics: Cell Polarity; Dose-Response Relationship, Radiation; Germination; Models, Biological; Pollen; Pollen Tube; Radiation, Ionizing
PubMed: 33124689
DOI: 10.1111/pce.13929 -
Plant Reproduction Sep 2023Sexual reproduction in angiosperms requires the production and delivery of two male gametes by a three-celled haploid male gametophyte. This demands synchronized gene...
Sexual reproduction in angiosperms requires the production and delivery of two male gametes by a three-celled haploid male gametophyte. This demands synchronized gene expression in a short developmental window to ensure double fertilization and seed set. While transcriptomic changes in developing pollen are known for Arabidopsis, no studies have integrated RNA and proteomic data in this model. Further, the role of alternative splicing has not been fully addressed, yet post-transcriptional and post-translational regulation may have a key role in gene expression dynamics during microgametogenesis. We have refined and substantially updated global transcriptomic and proteomic changes in developing pollen for two Arabidopsis accessions. Despite the superiority of RNA-seq over microarray-based platforms, we demonstrate high reproducibility and comparability. We identify thousands of long non-coding RNAs as potential regulators of pollen development, hundreds of changes in alternative splicing and provide insight into mRNA translation rate and storage in developing pollen. Our analysis delivers an integrated perspective of gene expression dynamics in developing Arabidopsis pollen and a foundation for studying the role of alternative splicing in this model.
Topics: Arabidopsis; Reproducibility of Results; Proteomics; Pollen; Transcriptome; Arabidopsis Proteins; Gene Expression Regulation, Plant
PubMed: 36282332
DOI: 10.1007/s00497-022-00452-5