Samičí gametofyt Gynaeceum Typy placentace, stavba vajíčka Megasporogeneze (vývoj megaspor) Megagametogeneze (vývoj zárodečného vaku) Základní typy gyneceí a placentace (Tachtadžan 1945) Gynaeceum Placentace I, II apokarpní pivoňka, pryskyřník magnolie povrchově boková nástěnná pl. parietalis laminaris povrchově středová pl. parietalis marginalis III synkarpní tulipán, lilie V lysikarpní hvozdík, primula komisurální úhlová pl. commisuralis axilaris nástěnná pl. parietalis středová pl.centralis IV parakarpní Příčný řez semeníkem 3 plodolisty axilární placentace Vývoj vajíčka Beschorneria Savčenko a Komar 1965 Základní typy vajíček Goebel 1933 ortotropní (atropní) anatropní přímé obrácené příčné hemitropní kampylotropní amfitropní Vztahy mezi typy vajíček Savčenko 1973 1 4 2 6 5 a b 3 c e d f hypertropní a orto-kampylotropní b ana-kampylotropní c orto-amfitropní d ana-amfitropní e orto-circinotropní f ana-circinotropní Vajíčka Johri 1984 Anatropní vajíčko - schéma Megasporogeneze = tvorba makrospor samičí archespor megasporocyt tetráda haploidních megaspor meióza Megagametogeneze = tvorba zárodečného vaku tetráda haploidních megaspor fungující megaspora (megaspory) mladý zárodečný vak zralý zárodečný vak = samičí gametofyt monosporický, bisporický, tetrasporický mitotická dělení diferenciace buněk Megasporocyt = mateřská buňka megaspor vnější integument vnitřní integument nucelus megasporocyt Meióza Přehled typů zárodečných vaků Erdelská 1981 (podle Maheshwari 1951) monosporické bisporické tetrasporické Polygonum 8 jaderný, bipolární Oenothera 4 jaderný monopolární Allium 8 jaderný, bipolární Podostemon 4 jaderný, monopolární Adoxa 8 jaderný, bipolární Fritillaria 8 jaderný, bipolární Plumbagella 4 jaderný, bipolární Drusa 16jaderný, bipolární Penea 16jaderný, polypolární Peperomia 16 jaderný, tetrapolární Plumbago 8 jaderný, tetrapolární Vývoj zárodečného vaku u Arabidopsis Grossnilaus a Schneitz 1998 Hejátko et al. 2003 vývojová stádia proximal distal anterior posterior MMC Regulace vývoje vajíčka Arabidopsis Megasporogeneze ve vajíčku lilie http://images.iasprr.org/lily/female.shtml Ranná profáze I v megasporocytu IASPR The parallel stripes in the cytoplasm are layers of endoplasmic reticulum. Initially, the nucleolus is prominent and centrally located. Mid prophase I in the megasporocyte. The nucleolus, tightly appressed to the nuclear envelope of the megasporocyte, forms a nucleolar cap. Chromosomes are paired at this stage (near pachytene) during crossing-over. IASPRR Telophase I in the megasporocyte. The nuclear envelopes frequently reform in monocots. The phragmoplast located between the dyad nuclei will disperse without forming a cell wall. IASPRR Dyad nuclei dividing: Metaphase II. The two dyad nuclei form a transverse spindle during the second half of meiosis. IASPRR Linear tetrad of megaspores At the conclusion of meiosis, there are four equal megaspore nuclei formed in lily. Since all four megaspore nuclei persist and contribute to the forming embryo sac, this is tetrasporic IASPRR Megagametogeneze u lilie Migration of megaspore nuclei Soon after their formation, three of the megaspore nuclei migrate to the chalazal end, while one remains in the micropylar end. As this occurs, a central vacuole enlarges IASPRR Preparation for the first mitotic division The micropylar and chalazal chromosomes condense prior to mitotic division. The micropylar end of the embryo sac will contain two 1N nuclei IASPRR The chalazal cluster becomes part of a common mitotic spindle and will reconstitute two 3N nuclei after the completion of mitosis Preparation for the first mitotic division IASPRR Anaphase during the first mitosis Ultimately, the mitotic assemble in the embryo sac form traditional spindles. The chromosomes in the chalazal end outnumber the micropylar ones by a 3:1 ratio IASPRR Metaphase during second mitosis. The micropylar nuclei develop spindles with perpendicular nuclei. The micropylar spindle is located transversely and will form the two synergids, while the more chalazal spindle of the two is at right angles and will form the egg and a polar nucleus IASPRR Among the chalazal products of mitosis, the spindles are also oriented perpendicular to one another. The chalazal of the two spindles is poorly formed, whereas the more central of the two spindles will form a polar nucleus and one antipodal Metaphase during second mitosis. IASPRR Maturing megagametophyte The four micropylar nuclei are all haploid (1N) nuclei that will form the egg, two synergids and one of the two polar nuclei IASPRR The large chalazal nucleus is the 3N polar nucleus. The adjacent cell is a 3N antipodal cell. Chalazal to this is another antipodal cell. Since the two chalazal nuclei never complete mitosis, only one cell (potentially 6N) is formed instead of two Maturing megagametophyte IASPRR Variabilita utváření antipod 1 42 3 5 6 1 Delphinium 2 Sedum 3 Butomopsis 4 Gentiana 5 Ligularia 6 Spargania 7 Trautweteria 8 Chrysocoma 9 Anthemis 10 Bidens 7 8 9 10 Synergidy a filiformní aparát Petunia Torenia Zea Gossypium Double fertilization The micropylar end of the embryo sac (to the right) contains a dense male nucleus and a less dense female nucleus, which will fuse to form the zygote IASPRR Chalazální konec zárodečného vaku The chalazal end of the embryo sac contains the fusing polar nuclei, which are less dense, with the darker male nucleus. This product of triple fusion forms a 5N endosperm (1N + 1N + 3N). IASPRR Triple fusion The nucleus to the left is the 3N (formerly chalazal) polar nucleus. In the center is the male (sperm) nucleus. On the right side is the 1N (formerly micropylar) polar nucleus IASPRR