4. Asymmetric cell division and their regularity Flashcards
What can induce or change cell polarity and asymmetric cell division?
Internal and external stimuli, daughter cells can adopt different cell fates (in some cases)
Example for the stimuli: proteins, light and gravity
Name one example for asymmetric cell division!
Zygotes of brown algea order Fucales like Fucales spec. and Pelvetia spec. perform asymmetric cell division after fertilization into an apical embryonic cell and a basal rhizoid cell, there is action accumulation at sperm entry, cell can react to light, 2 cells have to fates, localization of centriols give polarity achsis, orientation of the achsis depending on the stimulus
The algea blong to Heterokonta (eucaryotes with flagellum) which means that they’ve got centrosomes and centrioles
Which component has influence of of axis formation, cell division symmetry and the distribution of rhizoid cell fate in Fuctus zygotes?
The ARF-GEF and vesicle transport inhibitor brefilin A (BFA). This can mess up the cell fate.
How does a gnom mutant behave?
The asymmetric devision if Arabidopsis thaliana zygote is disturbed in gnom mutants. Zygote itself is not symmetric. The GNOM encodes a brefelinA sensitive ARF-GEF that is a direct target protein for BFA.
Give some examples for the asymmetric cell division in Arabidopsis embryos.
Not just an At but also in Fucus spec.: division in apical-basal asymmetry of zygote division
Formation of the protoderm by asymmetric periclinal (parallel to tissue or organ surface)
Formation of the lens-shaped cell and the daughter cell of the hypothesis by asymmetric hypophysal cell division
What does YODA it regulates and what is it?
It is a MAP kinase kinase kinase, regulation the zygote asymmetry, elongation and asymmetric cell division as well as the cell fate of the basal daughter cell, the suspensor.
From zygote to one-cell embryo: YODA determes which WOX in which cell (2 in apical, 8 in basal)
What contributed to the identification of many asymmetric cell division?
The measurements of cell volumes in the Arabidopsis embryo.
What does MONOPTEROS (MP)(=Auxin response factor 5) induces?
Induces TARGET of (MP) 7 (TMO7)), a basic-loop-helix transcription factor that moves from the precascular cells into the hypophysis where it is required for the asymmetric division into apical lens-shaped and basal hyphophyseal cell. It remains open whether similar factor contributes early lateral root formation.
What is special about the (Befruchtung) of At?
2 Befruchtungsevents: 1 sperm makes zygote and pollen tube, the other give rise to the endosperm (triploid endosperm)
Give some examples for asymmetric cell division in At!
Formation of Cotyledon, microspore division, root formation (Lateral root and main root), stoma formation
How does the microspore divide?
Divides into a small generative and a large vegetative cell, the former undergoes another division. (Before first division: nucleus goes a bit more to one side)
How is lateral root primorida initiated?
By asymmetric cell division of the pericycle
