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American Journal of Botany Jan 2020Variation in pollen-ovule ratios is thought to reflect the degree of pollen transfer efficiency-the more efficient the process, the fewer pollen grains needed. Few...
PREMISE
Variation in pollen-ovule ratios is thought to reflect the degree of pollen transfer efficiency-the more efficient the process, the fewer pollen grains needed. Few studies have directly examined the relationship between pollen-ovule ratio and pollen transfer efficiency. For active pollination in the pollination brood mutualisms of yuccas and yucca moths, figs and fig wasps, senita and senita moths, and leafflowers and leafflower moths, pollinators purposefully collect pollen and place it directly on the stigmatic surface of conspecific flowers. The tight coupling of insect reproductive interests with pollination of the flowers in which larvae develop ensures that pollination is highly efficient.
METHODS
We used the multiple evolutionary transitions between passive pollination and more efficient active pollination to test if increased pollen transfer efficiency leads to reduced pollen-ovule ratios. We collected pollen and ovule data from a suite of plant species from each of the pollination brood mutualisms and used phylogenetically controlled tests and sister-group comparisons to examine whether the shift to active pollination resulted in reduced pollen-ovule ratios.
RESULTS
Across all transitions between passive and active pollination in plants, actively pollinated plants had significantly lower pollen-ovule ratios than closely related passively pollinated taxa. Phylogenetically corrected comparisons demonstrated that actively pollinated plant species had an average 76% reduction in the pollen-ovule ratio.
CONCLUSIONS
The results for active pollination systems support the general utility of pollen-ovule ratios as indicators of pollination efficiency and the central importance of pollen transfer efficiency in the evolution of pollen-ovule ratio.
Topics: Animals; Flowers; Ovule; Pollen; Pollination; Symbiosis
PubMed: 31889299
DOI: 10.1002/ajb2.1412 -
The New Phytologist Feb 2021Cotton fiber is the most important source of cellulose for the global textile industry. These hair-like single-celled trichomes develop from ovule epidermis. They are...
Cotton fiber is the most important source of cellulose for the global textile industry. These hair-like single-celled trichomes develop from ovule epidermis. They are classified into long spinnable lint and short fuzz. A key objective in the cotton industry is to breed elite cultivars with fuzzless seeds carrying high lint yield. Molecular basis underlying lint and fuzz initiation remains obscure. Recent studies indicate fiber initiation is under the control of MYB-bHLH-WDR (MBW) transcription factor complex. Based on molecular genetic studies and gene expression patterns linking fiber phenotypes, we propose that specific but different sets of MBW genes are required to precisely regulate the initiation of the lint and fuzz fibers. Emerging evidence further points to sugar signaling as a 'hair-tonic' to boost fiber initiation through interaction with MBW complex and auxin signaling. An integrative model is provided as a conceptual framework for future studies to dissect the molecular network responsible for cotton fiber initiation.
Topics: Cotton Fiber; Gene Expression Regulation, Plant; Gossypium; Ovule; Plant Breeding; Plant Proteins; Seeds
PubMed: 32858773
DOI: 10.1111/nph.16898 -
Reproduction in Domestic Animals =... Jan 2023Mares are seasonally polyoestrous breeders. Therefore, the first ovulation of the season, following winter anoestrus, is the only cycle in which mares ovulate without...
The post-ovulatory rise in progesterone is lower and the persistence of oestrous behaviour longer during the first compared with the second cycle of the breeding season in mares.
Mares are seasonally polyoestrous breeders. Therefore, the first ovulation of the season, following winter anoestrus, is the only cycle in which mares ovulate without the presence of an old CL from the previous cycle. The objective of this study was to compare the length of oestrous behaviour, and plasma progesterone concentrations during the early post-ovulatory period between mares after the first and second ovulation of the breeding season. Overall, 38 mares and 167 oestrous periods were used in the study. From those, 11 mares were used during the first and subsequent oestrous period to measure and compare the post-ovulatory rise in progesterone concentration, whereas all the mares were used to compare the length of the post-ovulatory oestrous behaviour between the first and subsequent cycles of the breeding season. The persistence of the post-ovulatory oestrus was longer (p < .001) following the first ovulation of the year (median of 52 h) compared with the subsequent ovulations (median of 36 h for second and later ovulations groups; n = 38 mares). The progesterone concentration at any of the four 8 h-intervals analysed (28, 36, 76 and 84 h post-ovulation) was lower (p < .01) following the first versus the second ovulation of the year. By 36 h post-ovulation the progesterone concentration of mares at the second ovulation of the year had passed the threshold of 2 ng/ml (2.1 ± 0.33 ng/ml), whereas in the first cycle it was 1.2 ± 0.13 ng/ml. In conclusion, mares had lower progesterone concentrations in their peripheral circulation and longer persistence of oestrous behaviour following the first ovulation of the year compared with the second and subsequent ovulatory periods of the breeding season.
Topics: Female; Horses; Animals; Progesterone; Seasons; Ovulation; Anestrus; Ovulation Induction
PubMed: 36177828
DOI: 10.1111/rda.14273 -
Cell Structure and Function 2010Sexual reproduction in flowering plants requires pollen-tube guidance, which is thought to be mediated by chemoattractants derived from target ovules. To date, however,... (Review)
Review
Sexual reproduction in flowering plants requires pollen-tube guidance, which is thought to be mediated by chemoattractants derived from target ovules. To date, however, no convincing evidence has been reported of a particular molecule being the true attractant. Emerging data indicate that two synergid cells, which are on either side of the egg cell, emit a diffusible, species-specific signal to attract the pollen tube at the last step of pollen-tube guidance. Recently, it was demonstrated that LUREs (LURE1 and LURE2), cysteine-rich polypeptides secreted from the synergid cell, are the key molecules in pollen-tube guidance. In this review, we summarize the mechanism of pollen-tube guidance, with special focus on gametophytic guidance and the attractants.
Topics: Ovule; Peptides; Plant Proteins; Pollen Tube; Recombinant Proteins; Scrophulariaceae; Signal Transduction
PubMed: 20562497
DOI: 10.1247/csf.10003 -
The Plant Cell Jun 2020
Topics: Arabidopsis Proteins; Endosperm; Ovule; Seeds
PubMed: 32303661
DOI: 10.1105/tpc.20.00295 -
Journal of Plant Research Mar 2022Paeonia ludlowii (Stern & Taylor) D.Y.Hong, an endangered species, is indigenous to Tibet, China and propagated only by seed under natural conditions. Its natural...
Paeonia ludlowii (Stern & Taylor) D.Y.Hong, an endangered species, is indigenous to Tibet, China and propagated only by seed under natural conditions. Its natural reproduction is constrained by low fecundity. Excess seed abortion is a key factor restricting its natural reproduction, cultivation, introduction, and protection. Understanding the specific origin and occurrence of aborted ovules is important for the protection of offspring. Using serial sectioning analysis, we studied the process of pollination and fertilization of P. ludlowii and examined the characteristics of aborted ovules, developmental differences after flowering of normal and aborted ovules, and their ratios at different positions in P. ludlowii ovaries. During pollination, fertilization, and seed development, ovule abortion was frequent, with a random abortion position. There were three types of abortion, namely, abnormal pistil, sterile ovules, and embryo and endosperm abortions. Of these, embryo and endosperm abortions could be divided into early abortion and middle abortion. The early aborted ovules stopped growing on day 12, the endoblast and endosperm in the embryo sac aborted gradually. Furthermore, the shape of the embryo sac cavity changed. The volume of aborted ovules was significantly different from that of fertile ovules. At ripening, the external morphology of different types of aborted seeds was significantly different. The possible reasons for the abortion of the ovules are also discussed.
Topics: Fertilization; Ovule; Paeonia; Pollination; Seeds
PubMed: 35059894
DOI: 10.1007/s10265-021-01366-5 -
PloS One 2022Pollen grains are male gametophytes, an ephemeral haploid generation of plants, that commonly engage in competition for a limited supply of ovules. Since variation in...
Pollen grains are male gametophytes, an ephemeral haploid generation of plants, that commonly engage in competition for a limited supply of ovules. Since variation in reproductive capabilities among male gametophytes may influence the direction and pace of evolution in populations, we must be able to quantify the relative fitness of gametophytes from different sires. To explore this, we estimated the relative fitness of groups of male gametophytes in a dioecious, wind-pollinated model system, Cannabis sativa, by characterizing the non-abortion rate (measured via chemical staining) and viability (measured via in vitro germination) of pollen from multiple sires. Pollen viability quickly declined within two weeks of anther dehiscence, and pollen stored under freezer conditions did not germinate regardless of storage time. In contrast, pollen non-abortion rates declined slowly and persisted longer than the lifetime of a sporophyte plant under both room temperature and freezer conditions. Pollen samples that underwent both viability and non-abortion rate analysis displayed no significant correlation, implying that researchers cannot predict pollen viability from non-abortion rates, nor infer male gametophytic fitness from a single measure. Our work demonstrates two independent, differential approaches to measure proxies of male fitness in C. sativa.
Topics: Cannabis; Germ Cells, Plant; Ovule; Plants; Pollen
PubMed: 35797371
DOI: 10.1371/journal.pone.0270799 -
Current Biology : CB Feb 2021The plant hormone auxin is a fundamental regulator of organ patterning and development that regulates gene expression via the canonical AUXIN RESPONSE FACTOR (ARF) and...
The plant hormone auxin is a fundamental regulator of organ patterning and development that regulates gene expression via the canonical AUXIN RESPONSE FACTOR (ARF) and AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) combinatorial system. ARF and Aux/IAA factors interact, but at high auxin concentrations, the Aux/IAA transcriptional repressor is degraded, allowing ARF-containing complexes to activate gene expression. ARF5/MONOPTEROS (MP) is an important integrator of auxin signaling in Arabidopsis development and activates gene transcription in cells with elevated auxin levels. Here, we show that in ovules, MP is expressed in cells with low levels of auxin and can activate the expression of direct target genes. We identified and characterized a splice variant of MP that encodes a biologically functional isoform that lacks the Aux/IAA interaction domain. This MP11ir isoform was able to complement inflorescence, floral, and ovule developmental defects in mp mutants, suggesting that it was fully functional. Our findings describe a novel scenario in which ARF post-transcriptional regulation controls the formation of an isoform that can function as a transcriptional activator in regions of subthreshold auxin concentration.
Topics: Alternative Splicing; Arabidopsis; Arabidopsis Proteins; DNA-Binding Proteins; Gene Expression Regulation, Plant; Indoleacetic Acids; Ovule; Protein Isoforms; Transcription Factors
PubMed: 33275890
DOI: 10.1016/j.cub.2020.11.026 -
Journal of Experimental Botany Feb 2021Eukaryotic cells rely on the accuracy and efficiency of vesicular traffic. In plants, disturbances in vesicular trafficking are well studied in quickly dividing root...
Eukaryotic cells rely on the accuracy and efficiency of vesicular traffic. In plants, disturbances in vesicular trafficking are well studied in quickly dividing root meristem cells or polar growing root hairs and pollen tubes. The development of the female gametophyte, a unique haploid reproductive structure located in the ovule, has received far less attention in studies of vesicular transport. Key molecules providing the specificity of vesicle formation and its subsequent recognition and fusion with the acceptor membrane are Rab proteins. Rabs are anchored to membranes by covalently linked geranylgeranyl group(s) that are added by the Rab geranylgeranyl transferase (RGT) enzyme. Here we show that Arabidopsis plants carrying mutations in the gene encoding the β-subunit of RGT (rgtb1) exhibit severely disrupted female gametogenesis and this effect is of sporophytic origin. Mutations in rgtb1 lead to internalization of the PIN1 and PIN3 proteins from the basal membranes to vesicles in provascular cells of the funiculus. Decreased transport of auxin out of the ovule is accompanied by auxin accumulation in tissue surrounding the growing gametophyte. In addition, female gametophyte development arrests at the uni- or binuclear stage in a significant portion of the rgtb1 ovules. These observations suggest that communication between the sporophyte and the developing female gametophyte relies on Rab-dependent vesicular traffic of the PIN1 and PIN3 transporters and auxin efflux out of the ovule.
Topics: Arabidopsis; Arabidopsis Proteins; Indoleacetic Acids; Ovule; Pollen Tube
PubMed: 32939545
DOI: 10.1093/jxb/eraa430 -
Plant Reproduction Sep 2018Flowering plants display a large spectrum of seed architectures. The volume ratio of maternal versus zygotic seed tissues changes considerably among species and... (Review)
Review
Flowering plants display a large spectrum of seed architectures. The volume ratio of maternal versus zygotic seed tissues changes considerably among species and underlies different nutrient-storing strategies. Such diversity arose through the evolution of cell elimination programs that regulate the relative growth of one tissue over another to become the major storage compartment. The elimination of the nucellus maternal tissue is regulated by developmental programs that marked the origin of angiosperms and outlined the most ancient seed architectures. This review focuses on such a defining mechanism for seed evolution and discusses the role of nucellus development in seed tissues and nutrient partitioning at the light of novel discoveries on its molecular regulation.
Topics: Endosperm; Ovule; Seeds
PubMed: 29869727
DOI: 10.1007/s00497-018-0338-1