While bryophytes in general are more interesting than important, in the usual sense, a conspicuous exception are mosses of the genus Sphagnum. Peat also contains other plants such as reeds, that grow amid the sphagnum. In dried form, peat moss is remarkably absorbent and, and has been used for diapers, for enriching poor garden soils, and as a field dressing for wounds.
Whereas cotton absorbs times its dry weight, dried sphagnum can absorb 20 times its own weight in fluids! Peat bogs are very important and interesting ecosystems.
Division Hepaticophyta - 9, sp. Liverworts have the simplest bodies of all the green plants. The gametophyte, the dominant stage, looks like a flat scaly leaf, with prominent lobes.
During the Middle Ages, this similarity caused physicians to prescribe liverwort for diseases of the liver. According to the Doctrine of Signatures the Creator had designed all of nature, including plants, with our welfare in mind. People believed that plants had been intentionally designed to resemble the organs of the body they were supposed to heal!
Hence liver-wort, wyrt being the Anglo-Saxon word for herb. The shape of the liverwort was the signature of the Creator in nature. Can you guess what walnuts were supposed to cure? Liverworts share the general properties of bryophytes, but are not very closely related to mosses or hornworts. Many botanists think they may have evolved independently, from a different group of green algae.
If you get the aquatic liverwort Porella in lab, take a sniff of the jar, but not too deep! It smells of rancid oils, oils that went a little funky while the plant was being shipped. Another characteristic unique to liverworts is their lack of stomata, which are found in all other plants, including mosses and hornworts. In many species of liverworts, such as Marchantia , the one you will most likely see in lab, the antheridia and archegonia are not on top of the plant, but hanging down from the underside of odd little structures that look like tiny umbrellas.
These umbrella-shaped structures are called the antheridiophore and archegoniophore. The bi-flagellated sperm swims to the egg, and fertilization takes place to form a diploid 2N zygote. The tiny diploid sporophytes, which remain attrached to the parent plant, have a very simple structure. Meiosis within the sporophyte produces a number of haploid spores. These spores are surrounded by curious long and twisted moist cells called elaters. When the capsule dries and bursts, the elaters twist and jerk around in a way that scatters the spores in all directions.
Liverworts can also reproduce asexually by means of special structures called gemmae cups. These little cups can be easily seen on the surface of the plant. Each gemma cup contains a number of tiny plantlets called gemmae, and a single drop of water will disperse them. The green gametophytes of the hornwort look very much like a liverwort. But their small sporophytes more closely resemble those of mosses. The sporophytes grow out of the gametophyte, and look like a little upright horn. Like mosses, hornworts have stomata, and so are probably more closely related to mosses and other plants than to the liverworts they mat resemble.
These plants are symbiotic with the cyanobacteria Nostoc. The cyanobacteria fixes nitrogen for the hornwort. Division Hepaticophyta - liverworts Marchantia, Conocephalum, Porella; fr.
Examine the living mosses on display. Notice the small capsules on top of the tiny sporophytes. Mosses generally grow in one of two growth types: cushiony moss and feathery moss. Examine slides of the antheridia and archegonia. The sausage shaped antheridia produce sperm, and the flask shaped archegonia produces eggs.
Examine slides of the protonema. What type of algae does it remind you of? This resemblance is additional evidence that green algae gave rise to all higher plants. Examine the terrestrial liverworts Marchantia and Conencephalum one or both should be on display. How does their growth habit differ from that of the mosses? Can you see any gemmae cups on the upper surface of these plants? Examine the aquatic liverworts like Porella and Riccia one or both should be on display.
Notice how they differ from the more terrestrial forms of liverwort. Look at the preserved liverworts , and observe their distinct reproductive structures they look like little green umbrellas. How does their life cycle differ from mosses? Hint: Be sure you understand the general life cycle of plants, and can tell which stages are haploid gametophytes 1N or diploid sporophytes 2N.
We'll learn several life cycles in lecture and in lab moss, fern, pine, flowering plant , but all of them are variations on the same basic theme. Just as the evolution of spores was the key to the invasion of the land surface by bryophytes, the invention of complex vascular tissues let tracheophytes complete the conquest of dry land.
There are about , species of vascular plants, grouped in nine divisions. Tracheophytes all have a well developed root-shoot system, with highly specialized roots, stems, and leaves, and specialized vascular tissue xylem and phloem that function like miniature tubes to conduct food, water, and nutrients throughout the plant.
Because ferns and fern allies posses true vascular tissues, they can grow to be much larger and thicker than the bryophytes. The ferns and fern allies non-seed tracheophytes mark two major evolutionary strides. In these and in all more advanced plants, the leafy green diploid sporophyte now becomes the dominant stage. The tiny gametophyte may be either autotropophic like the fern prothallus or heterotrophic like the gametophytes of some lycopsids , and is generally free living and independent of the parental sporophyte.
Unlike the vascular sporophytes, the gametophytes have no vascular tissue at all. These gametophytes are therefore very small, and develop best in moist areas, where they can absorb water directly from their surroundings. Like the bryophytes, ferns and fern allies are still restricted to moist habitats. Their flagellated sperm need a thin film of water to swim between the antheridium and the archegonium.
And when the baby sporophyte grows up from the gametophyte, it is exposed to desiccation drying up. This basic strategy of a free-swimming sperm and a non-motile egg is shared by plants, animals, and algae. It makes sense, because it means only one set of gametes has to make the perilous journey outside of the organism.
The ferns and fern allies germinate from spores. These plants are mostly homosporous - their spores are identical and you can't differentiate which will grow into male or female plants. They are also monoecious - both the archegonia and antheridia male and female reproductive structures are borne on the same plant. Contrast these primitive vascular plants with the more advanced seed plants, the gymnosperms and angiosperms, which germinate from seeds rather than from spores.
Seed plants are all heterosporous. It is easy to differentiate the larger female megaspore from the smaller male microspore. The sperm of seed plants have no flagella. Examples are the integral component of the axoneme, such as Pacrg and hydin, both of which were originally identified as being related to Parkinson disease and hydrocephalus, respectively.
The Parkin-co-regulated gene product, Pacrg, is an evolutionarily conserved axonemal protein that functions in the formation of outer doublet microtubules Lorenzetti et al. Knockout of other axonemal or periaxonemal components, including Dnahc7 Neesen et al. Knockout mice lacking Jund1 , a gene for Jun-D transcription factor, show disorganization of microtubules and lack of structures such as RSs and dynein arms Thepot et al.
It is particularly intriguing that disruption of non-cytoskeletal components, such as Neur1 , VDAC3 or Sepp1 , results in defects or extrusion of specific outer doublets, implying that these genes are involved in the functional arrangement of the 9-fold outer doublet structure Sampson et al.
A list of human ciliopathy and mouse knock out affecting specific axonemal structure and sperm motility. Axonemal tubulins undergo several types of post-translational modifications, including acetylation, detyrosination, phosphorylation, palmitoylation, glutamylation and glycylation Huitorel et al. Recent research of the tubulin tyrosine ligase like TTLL family of proteins has revealed their significant role in the construction and regulation of axonemes.
A recent study has suggested that this abnormality is caused by the hyper-polyglutamylation of tubulin Rogowski et al. Although the mechanism of axoneme formation has yet to be understood in detail, accumulating knowledge demonstrates several key processes for ciliary and flagellar formation.
First, the forkhead box J1 and regulatory factor X family of transcription factors are important players in the control of ciliary gene expression for review, see Thomas et al. Second, IFT is a bidirectional movement driven by kinesin-II anterograde and cytoplasmic dynein retrograde to transport axonemal and membrane components for construction of cilia and flagella for review, see Cole, Furthermore, Lis1 is a WD-repeat protein that interacts with cytoplasmic dynein.
Knockout of Lis1 causes defects in flagella formation Pedersen et al. In mammals, IFT particle proteins are expressed in the testis and may be involved in the assembly of motile sperm flagella Baker et al. A mutation of IFT88 could lead to sperm with short or disorganized tails Pazour et al. Drosophila mutants lacking a homolog of IFT88 produce normal sperm, however, although they have defective sensory cilia Han et al.
The sperm phenotype of the IFT88 knockout mouse Tg has not been reported; therefore, it is unknown whether the IFT seen in other ciliogenesis is needed for the formation of sperm flagella.
Another mechanism necessary for ciliogenesis is cytoplasmic assembly of axonemal components and vesicular trafficking of membrane proteins from the Golgi to the ciliary membrane. The sliding of outer doublet microtubules by axonemal dyneins through a mechanochemical cycle of ATP hydrolysis is undoubtedly the driving force for the flagellar motility of sperm Satir, ; Summers and Gibbons, ; Brokaw, ; Shingyoji et al. Microtubule sliding is converted into the bending of axonemes if resistance to the sliding is present Shingyoji et al.
This resistance is present at the base of flagellum and between each bend. The bend is propagated from the base to the tip of the flagellum. The mechanism of dynein regulation and the propagation of microtubule sliding and its conversion into bending have been among the foremost research topics in this field.
Several theoretical models have tried to explain the mechanism of bend formation and propagation for review, see Lindemann, ; Ishijima, ; Brokaw, ; Woolley, Dyneins are minus-ended motors that move adjacent microtubules to the tip of the flagellum the plus end of the microtubules.
Flagellar bending is caused by the sliding of doublet microtubules, and the extent of bending correlates with the velocity of microtubule sliding Brokaw, , The flagellar waveform is composed of a bend with a larger angle principal bend and a bend with a smaller angle reverse bend; Brokaw, To achieve oscillation of flagellar bending, the sliding of specific microtubules and its displacement during the reverse direction of sliding are considered necessary.
In another words, dyneins on one side must be active while those on the other side are inactive to bend the axoneme Fig. Although the mechanism that switches dynein activity is incompletely understood, previous studies have suggested that the mechanical feedback from flagellar bending is important for the oscillatory movement.
Flagellar bending imposed by a microneedle increases microtubule-sliding velocity and switching of dynein activity, supporting the hypothesis that bending is involved in the force feedback and self-regulatory mechanisms underlying flagellar oscillation Morita and Shingyoji, A possible model for the oscillatory mechanism of flagellar bending. The axonemes are fixed at the basal body near the sperm head. The base or tip of the flagellum points toward the minus or plus end of doublet microtubules, respectively.
Dyneins are minus-ended motors red and pink arrows , sliding adjacent microtubules to the plus end black and gray arrows. The bending provides feedback and switches active dyneins, resulting in the sliding of opposite microtubules across the bend. Axonemes have two dynein motors with different properties: outer arm and inner arm.
Several studies, including those of Chlamydomonas mutants and the outer-arm extracted sea urchin sperm, indicate that outer or inner arm dyneins are involved in the elevation of microtubule sliding velocity increasing beat frequency and formation and propagation of flagellar bending, respectively Gibbons and Gibbons, ; Brokaw and Kamiya, Several dynein subspecies, especially inner arm dyneins, have different microtubule sliding properties Kagami and Kamiya, The central apparatus plays an important role in flagellar motility as evidenced by the paralysis of Chlamydomonas mutants with defective central apparatus structure.
Flagellar bending of these mutants has been experimentally induced Frey et al. Antibodies against RSs caused a loss of planar bend movement and the development of helical movement Gingras et al.
These observations suggest that the central apparatus is involved in determining the bending plane. Studies on Chlamydomonas flagella have shown that signals from the central apparatus activate specific dyneins for local bending Smith and Sale, ; Smith and Yang, The activation of sperm motility is observed at fertilization in most animals.
Several proteins have been described in this signaling pathway, and recent proteomic research indicates that multiple proteins are involved in the signaling and activation of axonemes Ficarro et al. The mechanism of dynein activation has not been fully elucidated, but the phosphorylation of the Tctexrelated LC of outer arm dynein and the dephosphorylation of an IC of inner arm dynein appears to be a prerequisite for the activation of outer or inner arm dynein, respectively Inaba et al.
Furthermore, proteins in other axonemal structures, such as a radia spoke protein LRR37, may be modified upon activation of sperm motility Hozumi et al.
One study has proposed that flagellar asymmetry is produced by the inhibition of reverse bend Brokaw, Google Scholar. Google Preview. Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide. Sign In or Create an Account. Sign In. Advanced Search.
Search Menu. Article Navigation. Close mobile search navigation Article Navigation. Volume Article Contents Abstract. Flagellar axoneme is a supramolecular protein complex with motors and regulatory structures. Unicellular algae Chlamydomonas : a model organism for studying the structure and function of eukaryotic cilia and flagella.
Marine invertebrate sperm: a model system for studying flagellar proteins and mechanisms of flagellar motility in metazoa. Sperm axonemes are surrounded by several accessory structures in mammals. Antibodies against sperm: a strategy to identify axonemal components. Human ciliopathy and knockout mice: insights into the mechanism of axonemal formation. Established and proposed mechanism for flagellar motility.
Regulatory mechanism of axonemal motility is important for fertilization. Editor's Choice. Sperm flagella: comparative and phylogenetic perspectives of protein components.
Shimoda Marine Research Center. Oxford Academic. Revision received:. Select Format Select format. Permissions Icon Permissions. Abstract Sperm motility is necessary for the transport of male DNA to eggs in species with both external and internal fertilization.
Figure 1. Open in new tab Download slide. Figure 2. Figure 3. Table I A list of human ciliopathy and mouse knock out affecting specific axonemal structure and sperm motility. Human or mouse gene. Protein product. Chlamydomonas protein. Protein localization. Defect in the axonemal structure. Pennarun et al. Outer dynein arm Outer dynein arm Duriez et al. Axoneme and tip of flagellum Several substructures Hunter et al.
Dynein regulatory complex Central pair, inner dynein arm Becker-Heck et al. Inner dynein arm Inner dynein arm, outer dense fiber Neesen et al.
Outer dense fiber Doublet microtubules Tarnasky et al. Doublet microtubules No. Mitochondrial membrane Doublet microtubules No. Flagellar extracellular protein Microtubule extrusion Olson et al. Axoneme assembly no flagellum Fernandez-Gonzales et al. Axoneme assembly no flagellum Thepot et al. Open in new tab. Figure 4. Electron microscopy of the sperm tail; results obtained with a new fixative.
Google Scholar Crossref. Search ADS. IFT20 links kinesin II with a mammalian intraflagellar transport complex that is conserved in motile flagella and sensory cilia. Calcium regulation of microtubule sliding in reactivated sea urchin sperm flagella. Google Scholar PubMed. Mutations in the DNAH11 axonemal heavy chain dynein type 11 gene cause one form of situs inversus totalis and most likely primary ciliary dyskinesia. The coiled-coil domain containing protein CCDC40 is essential for motile cilia function and left-right axis formation.
Association of kinesin light chain with outer dense fibers in a microtubule-independent fashion. IC defines a subdomain at the base of the I1 dynein that regulates microtubule sliding and flagellar motility. Axonemal tubulin polyglycylation probed with two monoclonal antibodies: widespread evolutionary distribution, appearance during spermatozoan maturation and possible function in motility.
Calcium-induced asymmetrical beating of triton-demembranated sea urchin sperm flagella. Microtubule sliding in swimming sperm flagella: direct and indirect measurements on sea urchin and tunicate spermatozoa.
Bending patterns of Chlamydomonas flagella. Mutants with defects in inner and outer dynein arms indicate differences in dynein arm function. Mutation of a novel gene results in abnormal development of spermatid flagella, loss of intermale aggression and reduced body fat in mice.
Proteomic profiling of accessory structures from the mouse sperm flagellum. Rethinking the relationship between hyperactivation and chemotaxis in mammalian sperm. The intraflagellar transport machinery of Chlamydomonas reinhardtii. Sperm-activating peptides in the regulation of ion fluxes, signal transduction and motility.
A knockin mouse model of the Bardet-Biedl syndrome 1 MR mutation has cilia defects, ventriculomegaly, retinopathy, and obesity. The Parkin co-regulated gene product, PACRG, is an evolutionarily conserved axonemal protein that functions in outer-doublet microtubule morphogenesis.
Differential light chain assembly influences outer arm dynein motor function. Expression of the human antigen SPAG2 in the testis and localization to the outer dense fibers in spermatozoa.
A common variant in combination with a nonsense mutation in a member of the thioredoxin family causes primary ciliary dyskinesia. A kinesin-like calmodulin-binding protein in Chlamydomonas : evidence for a role in cell division and flagellar functions. Egydio de Carvalho. Purkinje cell degeneration pcd phenotypes caused by mutations in the axotomy-induced gene, Nna1.
Phosphoproteome analysis of capacitated human sperm. Reactivation at low ATP distinguishes among classes of paralyzed flagella mutants. The probasal bodies and microtubules within the blepharoplast cavities are labeled with antibodies specific to acetylated tubulin. Positive but weak reactions of the blepharoplast core occur with the centrosomereactive antibodies MPM-2 and C Reactions to centrin antibodies are negative at this developmental stage.
From this pre-motility apparatus structure, an assemblage of about 1, flagella and associated structures arises as the precursor to the motility apparatus for the sperm. The flagellar apparatus consists of a three-layered multilayered structure that subtends a layer of spline microtubules, a zone of amorphous material similar to that in the blepharoplast, and the flagellar band. Centrin antibodies react strongly with the multilayered structure, the transition zone of the flagella, and fibrillar material near the flagellar base at the surface of the amorphous material.
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