However, the possibility of presence of carpel initials in primordial stages of flower development cannot be completely ruled out.
Our previous study provided direct functional evidence that the initial recruitment of primordial follicles is tightly regulated by PI3K signaling in oocytes, as oocyte-specific deletion of Pten at the primordial follicle stage leads to global activation of all primordial follicles [6].
The size of this initial pool of primordial follicles in part determines the reproductive lifespan of the female.
A main component of this bottleneck occurs during formation and initial divisions of primordial germ cells when mtDNA copy numbers are reduced to <200 per cell.
The recruitment (or the initial growth) of primordial follicles is defined by a dramatic enlargement of the oocyte itself, accompanied by proliferation and differentiation of the surrounding granulosa cells (11 14).
Think of all those initial molecules in the primordial soup after the earth's creation and then imagine all the potential new combinations that they could form spontaneously, simply by colliding with each other (or perhaps supported by some extra energy of a lightning strike).
Oparin's initial model implied that primordial atmosphere was reducing, dominated by methane and hydrogen gas [ 11, 12].
Precise synchronised signals are thought to mediate the initial stages of mammary primordial development, since early stages of mammary morphogenesis progress in a highly stereotypical manner [ 14].
