The tapetum: Its form, function, and possible phylogeny inEmbryophyta

Pacini, Ettore; Franchi, Gian Gabriele; Hesse, Michael

doi:10.1007/bf00983304

Cited by 345 publications

(225 citation statements)

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“…6d,e). These observations are in good agreement with previous reports that the sporopollenin material for perine and exospore is mainly supplied from the spores and spore sac cells 11,34 , where PpGAMYBs and PpCYP703Bs were expressed ( Supplementary Fig. S5).…”

Section: Molecular Characterization Of Smgamyb and Ppgamybssupporting

confidence: 93%

“…During the transition from premeiosis to young microspore stage, the expression of these genes was mainly limited to the tapetal cells and microspores in a pattern similar to that of a GA biosynthesis gene, GA3 oxidase (SmGA3ox; Fig. 2c-e), where the sporopollenin material is produced for the outer wall development [9][10][11][21][22][23] . Considering that GAMYBs, CYP703As and GA biosynthesis genes in flowering plants are also co-expressed in the tapetal cells and microspores 1,8,12,[24][25][26] , these observations indicate that SmGAMYB activity in these tissues of Selaginella is required to mediate GA signalling during the outer wall formation of microspores.…”

Section: Molecular Characterization Of Smgamyb and Ppgamybsmentioning

confidence: 99%

“…The SEM observations revealed that the outer exospore of microspores in mock-treated plants was formed as numerous sporopolleninous projections (Fig. 3a), the material of which originates exclusively from the tapetum and microspores 11,23 . The heights of the outer exospore projections of GA 4 -treated microspores were significantly greater than those of mock-treated microspores, whereas the microspores treated with uniconazole produced less and shorter outer exospore projections than did the mocktreated microspores (Fig.…”

Section: Molecular Characterization Of Smgamyb and Ppgamybsmentioning

confidence: 99%

“…In rice, CYP703A3 is an essential enzyme in sporopollenin biosynthesis, and its expression is positively regulated by a transcription factor, GAMYB, which is controlled by the GA signalling pathway 1,7,8 . Previous anatomical and in silico studies suggest that, similar to flowering plants, present-day bryophytes, including mosses, and lycophytes (lycopods) contain sporopollenin-containing outer walls on the surface of their spores and microspores [9][10][11] , and genes encoding CYP703 homologues have been detected in these genomes 12 . Curiously, however, one of the basal vascular plants, Selaginella, contains a functional GA perception system that is mediated by a GA receptor, GIBBERELLIN-INSENSITIVE DWARF1 (GID1), and suppressor proteins (DELLAs), whereas one of the basal land plants, Physcomitrella patens, does not contain this system [13][14][15][16] .…”

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The Gibberellin perception system evolved to regulate a pre-existing GAMYB-mediated system during land plant evolution

et al. 2011

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Gibberellin (GA) controls pollen development in flowering plants via the GAMYB transcription factor. Here we show that GAMYB is conserved in Selaginella moellendorffii (lycophyte) and Physcomitrella patens (moss), although the former contains the GA signalling pathway, the latter does not. In the lycophyte, GA treatment promotes the outer wall development on microspores, whereas treatment with GA biosynthesis inhibitors disturbs its development. Contrary, in the moss, GAMYB homologue knockouts also produce abnormal spores that resemble Selaginella microspores treated with GA biosynthesis inhibitors and pollen grains of rice gamyb mutant. Moreover, the knockouts fail to develop male organs, instead ectopically forming female organs. Thus, before the establishment of the GA signalling pathway, basal land plants, including mosses, contained a GAMYB-based system for spore and sexual organ development. Subsequently, during the evolution from mosses to basal vascular plants including lycophytes, GA signalling might have merged to regulate this pre-existing GAMYB-based system.Peer reviewe

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Section: Molecular Characterization Of Smgamyb and Ppgamybssupporting

confidence: 93%

Section: Molecular Characterization Of Smgamyb and Ppgamybsmentioning

confidence: 99%

Section: Molecular Characterization Of Smgamyb and Ppgamybsmentioning

confidence: 99%

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The Gibberellin perception system evolved to regulate a pre-existing GAMYB-mediated system during land plant evolution

et al. 2011

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“…The cells of secretory tapetum maintain their position, and eventually undergo degeneration in situ towards the end of pollen development (PACINI et al 1985). Although, in recent years, it has been known that tapetal cells undergo programmed cell death during degeneration (PAPINI et al 1999, WU andCHEUNG 2000), the time of the degeneration varies greatly from species to species.…”

Section: Discussionmentioning

confidence: 99%

Cytochemical and ultrastructural observations of anthers and pollen grains in Lathyrus undulatus Boiss

Vardar¹,

Ünal²

2011

Acta Botanica Croatica

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In Lathyrus undulatus Boiss. (Fabaceae), the young microspore stage of anther development was characterized by the enlarged secretory tapetal cells, which presented an intense reaction with regard to protein, insoluble polysaccharides and lipids. At bicellular pollen stage, the middle layer and the tapetum degenerated. After degradation of the tapetum, epidermis and single row U-shaped endothecium existed in the mature anther wall, and pollen grains remained in the locus. Young microspores had a spherical and centrally located nucleus with one or two nucleoli, many spherical lipid bodies and starchy plastids. A mature pollen grain contains insoluble polysaccharides, proteins, lipids and calcium. The mature pollen had the following morphological characteristics: 3-zonocolporate, prolate, tectate (imperforate) type of exine and perforate type of structure. The intine formed an important constituent portion of the wall, and consisted two sublayers: an outer intine (exintine) and an inner intine (endintine). The well-defined exine was made up of lipoidal substances and protein, but the intine composed of insoluble polysaccharides and protein.The bicellular state of the pollen grains persisted to anthesis.

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Stamens

Smyth

2010

Encyclopedia of Life Sciences

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Stamens are the male reproductive organs of flowers. Typically, a stamen is made up of a pollen‐producing anther borne on a filament. Pollen arises in four sporogenous regions within the anther. The sporogenous cells are surrounded by nutritive support cells, the tapetum. Mature pollen is released from the anther by dehiscence of the anther wall. The developmental identity of the stamen is conferred by the combined action of MADS transcription factors. Subsequent cellular differentiation is under the control of a cascade of other transcription factor and signalling genes now being identified. Male sterility is useful in plant breeding, and may arise by loss‐of‐function of these genes, as well as by defects in mitochondria (cytoplasmic male sterility). Differences in the structure of stamens are associated with the types of pollinators involved. Stamens evolved from the microsporangia‐bearing organs of early seed plants. Key Concepts: Pollen is generated in stamens, the male reproductive organs of flowers. Pollen arises from sporogenous cells within the anthers. Sporogenous cells are surrounded by the tapetum, a nutritive layer of support cells. Stamen identity is conferred by the action of MADS transcription factors controlling B, C and SEPALLATA function. The transcription factor SPOROCYTELESS is required for generation of the sporogenous cells. Other transcription factors and signalling kinases are required for the entire developmental cascade and are now being identified. Mature pollen is released by dehiscence of the anther wall through slits called stomia. The structure of stamens in a species is closely adapted to the specific pollinators involved for that species. Pollen is also generated in nonflowering seed plants (gymnosperms and various extinct lineages), but it arises in leaf‐like organs (microsporophylls) rather than stamens.

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The tapetum: Its form, function, and possible phylogeny inEmbryophyta

Cited by 345 publications

References 107 publications

The Gibberellin perception system evolved to regulate a pre-existing GAMYB-mediated system during land plant evolution

The Gibberellin perception system evolved to regulate a pre-existing GAMYB-mediated system during land plant evolution

Cytochemical and ultrastructural observations of anthers and pollen grains in Lathyrus undulatus Boiss

Stamens

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