Evolution of Angiosperm Pollen. 1. Introduction<sup>1</sup>

Wortley, Alexandra H.; Hong, Wang; Lu, Lu; D, Li; Blackmore, Stephen

doi:10.3417/2012047

Cited by 36 publications

(19 citation statements)

References 208 publications

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“…Recently, the diversity and evolution of palynological characters were documented across the angiosperms based on the most comprehensive classification APG III (2009). Many characters, such as exine structure and aperture features, have indicated key evolutionary transitions in pollen morphology and have proven to be informative at different taxonomic levels (Lu et al, 2015; Wortley et al, 2015). However, little is known about the genetic basis underlying pollen evolution.…”

Section: Introductionmentioning

confidence: 99%

Transcriptome Analysis of Hamelia patens (Rubiaceae) Anthers Reveals Candidate Genes for Tapetum and Pollen Wall Development

et al. 2017

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Studies of the anther transcriptome on non-model plants without a known genome are surprisingly scarce. RNA-Seq and digital gene expression (DGE) profiling provides a comprehensive approach to identify candidate genes contributing to developmental processes in non-model species. Here we built a transcriptome library of developing anthers of Hamelia patens and analyzed DGE profiles from each stage to identify genes that regulate tapetum and pollen development. In total 7,720 putative differentially expressed genes across four anther stages were identified. The number of putative stage-specific genes was: 776 at microspore mother cell stage, 807 at tetrad stage, 322 at uninucleate microspore stage, and the highest number (1,864) at bicellular pollen stage. GO enrichment analysis revealed 243 differentially expressed and 108 stage-specific genes that are potentially related to tapetum development, sporopollenin synthesis, and pollen wall. The number of expressed genes, their function and expression profiles were all significantly correlated with anther developmental processes. Overall comparisons of anther and pollen transcriptomes with those of rice and Arabidopsis together with the expression profiles of homologs of known anther-expressed genes, revealed conserved patterns and also divergence. The divergence may reflect taxon-specific differences in gene expression, the use RNA-seq as a more sensitive methodology, variation in tissue composition and sampling strategies. Given the lack of genomic sequence, this study succeeded in assigning putative identity to a significant proportion of anther-expressed genes and genes relevant to tapetum and pollen development in H. patens. The anther transcriptome revealed a molecular distinction between developmental stages, serving as a resource to unravel the functions of genes involved in anther development in H. patens and informing the analysis of other members of the Rubiaceae.

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Section: Introductionmentioning

confidence: 99%

Transcriptome Analysis of Hamelia patens (Rubiaceae) Anthers Reveals Candidate Genes for Tapetum and Pollen Wall Development

et al. 2017

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“…Wortley et аl . () analysed the morphology of angiosperm pollen grains in relation to modern phylogenies (APG III) and concluded that the inner structure and outlines of apertures are important characters, but they are difficult to be used because of data deficiency and difficulties in obtaining them. Without CLSM application, the internal surface of the exine revealing the endoaperture can be described only with help of SEM, on accidentally broken exines.…”

Section: Application Of Clsm To Palynological Objectsmentioning

confidence: 99%

Potential of CLSM in studying some modern and fossil palynological objects

Гаврилова

Zavialova

Tekleva

et al. 2017

Journal of Microscopy

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We have tested possibilities and limitations of confocal laser scanning microscopy to study the morphology of pollen and spores and inner structure of sporoderms. As test objects, we used pollen grains of the modern angiosperm Ribes niveum (Grossulariaceae) and Datura metel (Solanaceae), fossil angiosperm pollen grains of Pseudointegricorpus clarireticulatum and Wodehouseia spinata dated to the Late Cretaceous, fossil gymnosperm pollen grains of Cycadopites-type dated to the Middle Jurassic, and fossil megaspores Maexisporites rugulaeferus, M. grosstriletus, and Trileites sp. dated to the Early Triassic. For comparative purpose, we studied the same objects with application of conventional light, scanning electron (to entire pollen grains and spores or to semithin sections of their walls), or transmission electron microscopy. The resolution of confocal microscope is much lower than that of electron microscopes, as are its abilities to reconstruct the surface patterns and inner structure. On the other hand, it can provide information that is unreachable by other microscopical methods. Thus, the structure of endoapertures in angiosperm pollen grains can be directly observed. It is also helpful in studies of asymmetrical pollen and pollen grains bearing various appendages and having complicated exine structure, because rotation of 3-D reconstructions allows one to examine all sides and structures of the pollen grain. The exact location of all visible and concealed structures in the sporoderm can be detected; this information helps to describe the morphology and inner structure of pollen grains and to choose necessary directions of further ultrathin sectioning for a transmission electron microscopical study. In studies of fossil pollen grains that are preserved in clumps and stuck to cuticles, confocal microscope is useful in determining the number of apertures in individual pollen grains. This can be done by means of virtual sections through 3-D reconstructions of pollen grains. Fossil megaspores are too large and too thick-walled objects for a confocal study; however, confocal microscope was able to reveal a degree of compression of fossil megaspores, the presence of a cavity between the outer and inner sporoderm layers, and to get some information about sporoderm inner structure.

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“…The widespread reiteration of exine patterns (e.g. reticulate, columellate, white‐lined lamellae) clearly points to these patterns being based on some physical principles of space‐filling operations (Scott, ) and has often been recognized in phylogenetic studies as widespread homoplasy (Doyle & Le Thomas, ; Wortley et al , ; Minelli, ). Our studies of sporoderm ontogeny in more than 30 species from a wide variety of taxa (see references in Gabarayeva et al , ; Gabarayeva et al , ) and data of other authors (e.g.…”

Section: Introductionmentioning

confidence: 99%

Artificial pollen walls simulated by the tandem processes of phase separation and self‐assemblyin vitro

2019

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Despite numerous attempts to elucidate the developmental mechanisms responsible for the observed diversity of pollen and spore walls, the processes involved remained obscure until the structures observed during exine development were recognized as a sequence of selfassembling micellar mesophases. To confirm this, a series of in vitro experiments was undertaken in which exine-like patterns were generated in colloidal mixtures by self-assembly, without any genomic participation. The intention was to test whether all the main types of exine structure could be simulated experimentally.Mixtures of substances, analogous to those involved in microspore development, were left undisturbed while water evaporated and self-assembly occurred. We varied the substances, their combinations and concentrations, and the physical constraints to make the experiments closer to the situation in nature. The resulting dry films were then examined using transmission electron microscopy.A variety of microstructures, simulating the full range of exine types, was obtained by micellar self-assembly. Moreover, the signs of related physicochemical process (i.e. phase separation) were also observed.Simple, energy-efficient, physical-chemical interactions, phase separation and self-assembly, are capable of generating exine-like patterns, providing evidence that these processes share control of exine formation with the well-documented program of gene expression.

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Evolution of Angiosperm Pollen. 1. Introduction¹

Cited by 36 publications

References 208 publications

Transcriptome Analysis of Hamelia patens (Rubiaceae) Anthers Reveals Candidate Genes for Tapetum and Pollen Wall Development

Transcriptome Analysis of Hamelia patens (Rubiaceae) Anthers Reveals Candidate Genes for Tapetum and Pollen Wall Development

Potential of CLSM in studying some modern and fossil palynological objects

Artificial pollen walls simulated by the tandem processes of phase separation and self‐assemblyin vitro

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Evolution of Angiosperm Pollen. 1. Introduction1

Cited by 36 publications

References 208 publications

Transcriptome Analysis of Hamelia patens (Rubiaceae) Anthers Reveals Candidate Genes for Tapetum and Pollen Wall Development

Transcriptome Analysis of Hamelia patens (Rubiaceae) Anthers Reveals Candidate Genes for Tapetum and Pollen Wall Development

Potential of CLSM in studying some modern and fossil palynological objects

Artificial pollen walls simulated by the tandem processes of phase separation and self‐assemblyin vitro

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Evolution of Angiosperm Pollen. 1. Introduction¹