34. Vaisinė muselė (Drosophila melanogaster) – vienas populiariausių
genetinių tyrimų objektų
Muselė turi mažiau genų (apie 14000) nei nematodas (kirmėlė) – 19000.
Tačiau vienam genui muselėje tenka 2 kartus daugiau nekoduojančios
DNR (10000 nt), nei nematode (5 000 nt)
35. Pirminio kūno plano susidarymo
genetinė kontrolė
• Priekinės-užpakalinės kūno ašies
susidarymas;
• Nugarinės-pilvinės (dorsoventralinės)
ašies susidarymas;
37. Branduolio (-ių) skilimas Drosophila embrione
Nuotraukos, gautos kofokaliniu mikroskopu. Pirmieji branduolio dalimaisi
vyksta zigotos centre. Skaičiai nurodo ląstelės ciklą. Po 13-o ciklo įvyksta
celiuliarizacija, susidaro blastoderma.
40. Musės kūnas padalintas į segmentus ir parasegmentus. Segmentacijos
proceso genetika intensyviai tiriama
Embrioną sudaro priekinė dalis (G +K), užpakalinė dalis (P) ir kūno galai
41. Bicoid mRNR ir baltymo gradientai D.
melanogaster embrione
48. Homeoseką turintys Drosophila genai
Homeziniai mutantai
Normali musė
Papildomi sparnai!
Ultrabithorax fenotipas, gautas
sukryžminus bitxorax ir postbithorax
mutantus
Antenos virtę kojomis!
Antp (Antennapedia) geno mutantas
Carroll S.B. et al. From DNA to Diversity (2001) Blackwell Science
49. Aštuoni homeoziniai (Hox) genai apsprendžia
įvairių muselės embriono ir suaugėlio segmentų
tapatumą
Suaugėlis
Embrionas
Carroll S.B. et al. From DNA to Diversity (2001) Blackwell Science
50.
51. Hox genai yra paralogai, turintys labai konservatyvią homeodomeno sritį
Kartotinis homeodomeno srities palyginimas:
Hox genai yra transkripcijos reguliatoriai, o homeosekos koduojamas
homeodomenas yra su DNR sąveikaujantis domenas.
Homeoseka (homeobox) koduoja apie 60 aminorūgščių
Carroll S.B. et al. From DNA to Diversity (2001) Blackwell Science
56. HOXB komplekso genų raiška pelės embrione
Hox genai (Hoxb-2 ir Hoxb-4) sujungti su reporteriniu lacZ genu. Pastarojo raišką
galima stebėti pagal spalvinę reakciją
57. Segmentacija ir HoxB genų raiška viščiuko užpakalinėse smegenyse
Spalvinis genų žymėjimas atitinka dešiniajame paveiksle pateiktą žymėjimą.
58. Daugialąsčių (Metazoa) Hox genų filogenija
Carroll S.B. et al. From DNA to Diversity (2001) Blackwell Science
62. Trachėjinio medžio formavimasis
Branchless geno raiškos
sritys nuspalvintos žalia
spalva (A)
EMBO reports 3, 6, 563–568
(2002)
doi:10.1093/embo-reports/kvf115
Published online: June 2002
113. Šviesoje fitochromo I (phyA) kiekis smarkiai sumažėja dėl
PHYA geno raiškos slopinimo ir/arba dėl phyA proteolizės
Fitochromas II (phyB-phyE) Pfr forma yra stabilesnė šviesoje nei fitochromo I
Editor's Notes
The key to understanding the initiation of sporulation is understanding the mechanism of Spo0A phosphorylation. We have shown that the pathway to Spo0A activation is a sequential series of phosphorylation reactions termed a multicomponent phosphorelay (Fig.2). The initial event in the phosphorelay is the activation of multiple kinases that phosphorylate the sporulation-specific response regulator Spo0F in response to environmental and metabolic signals. Spo0F acts as a secondary messenger, accumulating phosphate groups from developmentally activated kinases. Phosphorylated Spo0F (Spo0F~P) is the substrate for the Spo0B protein phosphotransferase that phosphorylates Spo0A. In this pathway, the signal-transduction event is the activation of the kinases to autophosphorylate. This is followed by three sequential phosphotransferase reactions that produce Spo0A~P, the crucial transcription regulator for sporulation
Tracheal network formation. ( A ) Scheme of tracheal development during stage 12. Tracheal cells (red) and Branchless-expressing cells (green) are indicated. ( B ) Whole-mount in situ double hybridization of 1-eve-1 embryos at stage 12 using lacZ (red) and hb (blue) antisense RNA probes. 1-eve-1 embryos reveal lacZ marker gene expression in the tracheal cells (red). The bridge-cell (arrows; revealed by hb expression) serves as a guidance post for the dorsal trunk branches. EMBO reports 3 , 6, 563–568 (2002) doi:10.1093/embo-reports/kvf115 Published online: June 2002
Constitutive activation of the Branchless (Bnl) signalling pathway can partially rescue the hb and hth dorsal trunk (DT) phenotype. Bnl signalling was induced with the arm-Gal4 and UAS-bnl transgenes ( B , E , H , K ), or with the recombinant Btl-Gal4 / UAS–actin–GFP (green fluorescent protein) and UAS-Btltor transgenes ( C , F , I , L ). Embryos are stained with anti-2A12 (green) and anti-Blistered/DSRF (red; A , B , D , E , G , H , J , K ), or with 2A12 (green) and anti-GFP ( C , F , I , L ). Embryos were triple stained with anti- -galactosidase to identify homozygous mutants by the absence of the blue balancer. ( A – C ) Wild-type (WT) embryos. ( D – F ) Homozygous bnlP1 mutant embryos. ( G – I ) Homozygous hbFB mutant embryos. ( J – L ) Homozygous hthP2 mutant embryos. ( M – O ) Graphical representation of the number of DT metameres observed (abscissa) per embryo (as a percentage; Y -axis), either in the mutant (red curves) or in the rescue (green and blue curves) context. In each situation, the total number ( n ) of embryos scored with the corresponding genotype is indicated. ( M ) Statistical representation of the bnlP1 DT phenotype compared with the two rescue situations. ( N ) Statistical representation of the hbFB DT phenotype compared with the two rescue situations. ( O ) Statistical representation of the hthP2 DT phenotype compared with the two rescue situations. A supplementary curve (in black) illustrates the
Stages of germ cell migration in mice. The time of onset of each step is indicated at the top right of each panel. E stands for embryonic day. The genes required for each step are shown in the bottom right of each panel. ( a ) Germ cells ( yellow ) are specified in the primitive streak. At E7.5, they initiate their migration to the endoderm ( orange ). An enlargement of the boxed area is shown on the right. In b – d a transverse section ( straight black line ) is shown at the right of each panel. ( b ) At E8, germ cells start migrating within the endoderm (which now becomes hindgut). ( c ) At E9.5, germ cells can be seen migrating from the hindgut toward the dorsal body wall. ( d ) By E10.5, germ cells reach the genital ridges ( green ) from the body wall to form the gonad; germ cells at the base of the mesentery will be lost. Consult text and Table 2 for detailed descriptions of each step and the functions of the genes named. This figure is adapted from Santos & Lehmann 2004a and Starz-Gaiano & Lehmann 2001.
At the midblastula stage, higher -Catenin levels on the dorsal side of the embryo, together with the vegetally located transcription factor VegT and the maternal TGF- -family growth factor Vg1, generate a gradient of Nodal-related molecules expressed in the endoderm. In turn, this gradient induces the formation of overlying mesoderm: low doses of Nodal-related molecules (Xnrs) lead to the formation of ventral mesoderm, whereas high doses lead to the establishment of Spemann's organizer. Nieuwkoop's centre is the region of dorsal endoderm that induces organizer tissue. At the gastrula stage, the organizer secretes a cocktail of factors that refine the initial patterning. Note that -Catenin is widely distributed on the dorsal side, including in derivatives of the three germ layers. (CNS, central nervous system.)
Cells on the ventral side of the blastula secrete a variety of proteins such as b one m orphogenetic p rotein-4 ( BMP-4 ) These induce the ectoderm above to become epidermis . If their action is blocked, the ectodermal cells are allowed to follow their default pathway , which is to become nerve tissue of the brain and spinal cord. The Spemann organizer blocks the action of BMP-4 by secreting molecules of the proteins chordin and noggin Both of these physically bind to BMP-4 molecules in the extracellular space and thus prevent BMP-4 from binding to receptors on the surface of the overlying ectoderm cells. This allows the ectodermal cells to follow their intrinsic path to forming neural folds and, eventually, the brain and spinal cord
Cells on the ventral side of the blastula secrete a variety of proteins such as b one m orphogenetic p rotein-4 ( BMP-4 ) These induce the ectoderm above to become epidermis . If their action is blocked, the ectodermal cells are allowed to follow their default pathway , which is to become nerve tissue of the brain and spinal cord. The Spemann organizer blocks the action of BMP-4 by secreting molecules of the proteins chordin and noggin Both of these physically bind to BMP-4 molecules in the extracellular space and thus prevent BMP-4 from binding to receptors on the surface of the overlying ectoderm cells. This allows the ectodermal cells to follow their intrinsic path to forming neural folds and, eventually, the brain and spinal cord
Figure 1 : Parallel vs. serial/sequential segmentation. The two species of insects shown here show two extreme cases of parallel (fruit fly, Drosophila ) and serial (locust, Schistocerca gregaria ) segmentation. Most insects show a combination of these two mechanisms. In Drosophila , an initial morphogen gradient is translated into 14 stripes through intermediate striped steps. The colored patterns show typical expression patterns of different classes of segmentation genes (brown: gap genes, green: pair-rule genes, gray: segment-polarity genes). Note that the embryo is a syncytium at all stages except the last one shown and no tissue growth is involved in the segmentation process (after Ingham, 1988 ). In Schistocerca , the embryo starts unsegmented. The first three morphological segments to appear are thoracic segments. Abdominal segments are then added in a sequential manner. The gray stripes represent the expression domain of the segment-polarity gene engrailed (after Sander, 1976 ; Patel, 1994 ).
Figure 2 : Vertebrate somitogenesis: (A) Schematic representation of somite formation in chicken. Cells become incorporated into the pre-somitic mesoderm (PSA) as Hensen's node (represented by a triangle) moves posteriorly through the embryo. Somites (S1, ... , S12) form each 90 mins along the developing spinal cord (dark gray) at a fixed distance from Hensen's node. The black spot represents a cell at its fixed position in the PSM, developing into a somite cell 18 hrs after being incorporated into the PSM (redrawn, with permission, from Palmeirim et al., 1997 ). (B) Schematic representation of oscillatory gene expression patterns observed during the formation of one somite. The expression starts in a broad posterior domain and narrows down as it advances anteriorly until it becomes fixed into one half of the newly formed somite. A anterior, P posterior, S somites (redrawn, with permission from Palmeirim et al., 1997 ).
Asymmetric Organization of Visceral Organs in Humans The normal arrangement (see text for description) of organs is called situs solitus. In right isomerism, also called asplenia syndrome, the heart, lung and liver are double-right, and the spleen in absent. Isomerism can also be used to describe LR defects of individual organs. Situs inversus totalis is the complete mirror image reversal of all organ asymmetry. This figure represents only a portion of the whole range of possible LR defects
Situs formation in mammals. (A) Proposed pathway for left-right axis formation in the mouse. The leftward movement of cilia in the node activates some as yet unidentified factor (possibly the product of the inv gene). This product activates the nodal and lefty2 genes. The diffusion of Nodal and Lefty2 proteins to the right-hand side is restricted by the product of the Lefty1 gene which coats the bottom of the neural tube on the left side. Nodal activates Pitx2, the gene whose product activates left-sided properties in the various organs containing it. Either Nodal or Lefty2 (perhaps both) repress the Snail gene whose product is needed to instruct right-sidedness. (B) Ciliated cells of the mammalian node. This photograph is a close-up of the node seen in Figure 11.29A . (Photograph courtesy of K. Sulik and G. C. Schoenwolf.)
Figure 1. Pathways regulating flowering time in Arabidopsis. The autonomous pathway regulators and vernalization repress FLC expression. FRI and FRL1 upregulate FLC expression, and the H3-K4 trimethylation mediated by the PAF1 complex (ELF7, ELF8 and VIP4) activates FLC expression. FLC represses expression of the ‘flowering-time integrators’ SOC1 and FT, whereas the photoperiod pathway promotes expression of these integrators. SOC1 and FT expression leads to the induction of floral-meristem-identity genes such as LEAFY and AP1, and thus of flowering. Lines with arrows indicate upregulation (activation) of gene expression and lines with bars for gene repression. Abbreviations: AP1, APETALA 1; CO, CONSTANS; EFS, EARLY FLOWERING IN SHORT DAYS; ELF7, EARLY FLOWERING 7; ELF8, EARLY FLOWERING 8; FLC, FLOWERING LOCUS C; FLD, FLOWERING LOCUS D; FLK, FLOWERING LOCUS K; LD, LUMINIDEPENDENS; PIE1, PHOTOPERIOD INDEPENDENT EARLY FLOWERING 1; SOC1, SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1; VIN3, VERNALIZATION INSENSITIVE 3; VIP3, VERNALIZATION INDEPENDENCE 3; VIP4, VERNALIZATION INDEPENDENCE 4; VRN1, VERNALIZATION 1; VRN2, VERNALIZATION 2.
FIGURE 24.6 The ABC model for the acquisition of floral organ identity is based on the interactions of three different types of activities of floral homeotic genes: A, B, and C. In the first whorl, expression of type A (AP2) alone results in the formation of sepals. In the second whorl, expression of both type A (AP2) and type B (AP3/PI) results in the formation of petals. In the third whorl, the expression of B (AP3/PI) and C (AG) causes the formation of stamens. In the fourth whorl, activity C (AG) alone specifies carpels. In addition, activity A (AP2) represses activity C (AG) in whorls 1 and 2, while C represses A in whorls 3 and 4.
FIGURE 17.4 Structure of the Pr and Pfr forms of the chromophore (phytochromobilin) and the peptide region bound to the chromophore through a thioether linkage. The chromophore undergoes a cis–trans isomerization at carbon 15 in response to red and far-red light. (After Andel
FIGURE 17.6 Phytochrome is most heavily concentrated in the regions where dramatic developmental changes are occurring: the apical meristems of the epicotyl and root. Shown here is the distribution of phytochrome in an etiolated pea seedling, as measured spectrophotometrically. (From Kendrick and Frankland 1983
