Protists — The phylum of the leading flagellar
Choanoflagellate is a protist that is a single cell or population. A group with a flagella that resembles a freshwater sponge, and the surface of the tyrosine kinase receptor also resembles a sponge, and is thought to be a sister group of animals.
<h1 class="pgc-h-arrow-right" data-track="4" > etymology</h1>
The scientific name Choanoflagellate is derived from the Greek Khoanē (pronounced "funnel" or "collar") and the Latin flagellum (meaning flagella).
<h1 class="pgc-h-arrow-right" data-track="6" >2</h1>
Each collared flagellar has a flagella, surrounded by a ring of actin-filled protrusions called microvilli, forming a cylindrical or vertebral "collar" outside the flagella, in name with it. The movement of the flagella can be pumped through the "collar", and bacteria and debris will be caught by the microvilliers, which will then be eaten by the collared flagellar. The water generated by the flagella also pushes the cells so that they can swim freely, like animal sperm. Relatively speaking, other flagellars tend to "pull" the flagellar to move through the movement of their flagella.
<h1 class="pgc-h-arrow-right" data-track="8" >3. Structure and evolution</h1>
At present, the entire gene of two species and the gene of the transcriptome of two species have been completely sequenced and published, facilitating the study of the collared flagella and biological evolution.
<h1 class="pgc-h-arrow-right" data-track="10">（1）Monosiga brevicollis</h1>
Monosiga brevicollis is a single-celled aquatic animal with a special structure: its tentacles are collar-like around the flagella, the same basic structure of the collar cells that form sponges (the most primitive multicellular organisms). Its genes are 41.6 Mbp, which is similar to the number of genes of filamentous fungi and other free-living single-celled organisms, but far less than that of ordinary animals.
The Sark Institute of Biology found that the Tyrosine Kinases gene of the flagellar is as high as 128, 38 more than those found in humans, and the tyrosine kinase regulatory network has a significant role in the evolution of later animals. It is generally believed that tyrosine kinase regulation is carried out only in multicellular animals, and the increasingly complex evolution of tyrosine kinase regulatory networks has led to the complex evolution of multicellular animals themselves. But the collared flagellar, which is a single-celled animal, is the only exception found so far.
An evolutionary genomics study found that multiple genes from blue-green algae were found in the genome of the collared flagellate. The scholars in charge of the study believe that it is possible that in the evolutionary history of the early basis, when the leading flagellar preyed on the blue-green algae for food through phagocytosis, the genes of the blue-green algae remained and fused in the collared flagellar.
Another study found that the gene of the laureate has a gene called GKPID (GK Protein-interaction domain) that controls the direction of its flagella as cells divide. This gene is thought to mark the evolutionary history of single-celled organisms transitioning to multicellular organisms.
<h1 class="pgc-h-arrow-right" data-track="15">（2）Salpingoeca rosetta</h1>
Salpingoeca rosetta has a gene size of 55 Mbp. Homologs of genes for cell adhesion, neuropeptides and sphingolipid metabolism are present in the genome.
<h1 class="pgc-h-arrow-right" data-track="17" > (3) Monosiga ovata's transcriptome</h1>
An EST dataset from Oval nematode was published in 2006, and the main finding of this transcriptome was the Hoglet domain of the weekly flagellar and elucidated the role of domain shuffle in the evolution of the Hedgehog signaling pathway.
<h1 class="pgc-h-arrow-right" data-track="19" >(4)Stephanoeca diplocostata transcriptome</h1>
The transcriptome of this species is the first discovery of a silicon transmission gene in the genus Lavender with sand shells that causes lavender. Subsequently, a similar gene was found in another sand-shelled species, Diaphanoeca grandis. By analyzing these genes, the CITRACH are homologous to the diatom SIT-type silicon transporter and evolve through horizontal gene transfer.
<h1 class="pgc-h-arrow-right" data-track="21" >4</h1>
Flagella are the organelles of many single-celled organisms and some multicellular organisms with a surface like a whip, which are used for movement and some other functions. In the three domains, the structure of the flagella varies. The flagella of bacteria is a spiral-like fiber that rotates like a screw and belongs to the rotational motion in living systems. The flagellar of archaea is superficially similar to that of bacteria, but many details are different, and the flagella of bacteria may not be homologous. The flagella of eukaryotes, such as animal, plant, and protists, are protrusions with complex structures on the surface of cells, whipping back and forth like whips.
< h1 class="pgc-h-arrow-right" data-track="23" >(1) type</h1>
Three types of flagella have been distinguished: bacterial, archaea, and eukaryotes.
The main differences between these three types are summarized below:
The bacterial flagella are spiral filaments, each with a rotating motor at its base that can be rotated clockwise or counterclockwise. They provide two movements in several types of bacterial motility.
Archaella is superficially similar to bacterial flagella, but differs in many details and is considered non-homologous.
Eukaryotes' flagellations: Complex cellular protrusions of plant, animal and protists' cells whipp back and forth like whips.
<h1 class="pgc-h-arrow-right" data-track="29" >(2) Bacterial flagellar</h1>
Different species of bacteria have different numbers of flagella. Monotrichous bacteria have a single flagella (such as Vibrio cholerae). Lophotrichous bacteria have multiple kinds of flagella that sit on the same surface as the bacteria, and act in concert to move the bacteria in a single direction.
Some bacteria, such as selenomonas, have extracellular tissues in the flagella.
<h1 class="pgc-h-arrow-right" data-track="32" >(3) archaeal flagella</h1>
The flagellar of archaea appears on the surface to resemble the flagella of bacteria. But in the 1990s, researchers discovered specific differences between archaea and bacterial flagella, including:
Bacterial flagella are driven by flowing protons, while paleoflage is almost certainly driven by adenosine triphosphate.
Bacterial cells tend to have many filaments of flagellar, and archaeal flagella are made up of many filaments in a bundle.
<h1 class="pgc-h-arrow-right" data-track="36" >(4) eukaryote flagella</h1>
The flagella of eukaryotes is made up of 9+2 microtubules that wiggle with ATP pulling the microtubules using dynamoproteins. Flagella is antigenic and induces the host to produce antibodies.
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