Month: September 2022

EGG DOMINATED FATES. "Fate specification within the reduced gametophytes of flowering plants is also dependent on intercellular signaling. In embryo sacs, the egg, once specified via a hormone gradient, assumes a dominant role and generates signals that determine the fates of its neighbors." http://www.sciencedirect.com/science/article/pii/S1534580713000427 View in LinkedIn

SILENCING WORK. "Once cell fates are specified within the gametophytes, the current data suggest that “information flow” reverses with the companion cells of the pollen and embryo sac acting to silence transposable elements in the germ cells. Presumably, this would act to reinforce the default systems that repress transposable element activity in somatic cells, perhaps because of an increased requirement for genome integrity in the gametes caused by the gametic chromatin being differently packed from that of somatic cells." http://www.sciencedirect.com/science/article/pii/S1534580713000427 View in LinkedIn

PRESERVING GENOME FIDELITY. "Companion cell DNA does not contribute to the zygotic genome, and therefore reactivation of companion cell transposable elements does not risk the genome fidelity of the next generation. Together with its vital biological function to facilitate fertilization and promote postfertilization development with reduced dependence on water, the ability of the gametophyte to protect the integrity of the zygotic genome has probably contributed to the maintenance of this distinct “generation” during angiosperm evolution." http://www.sciencedirect.com/science/article/pii/S1534580713000427 View in LinkedIn

CONTROLLING TRANSPOSONS. "Exonization of transposable elements sequences supplies the genome with a source of genetic material for evolution. Uncontrolled activity of transposable elements, however, causes deleterious effects, as evidenced in both plants and animals." https://lnkd.in/dwPiXaA View in LinkedIn

CONTINUED THREAD. "Importantly, the supporting roles of the male and female companion cells do not end with gamete maturation. After pollen germination on the stigma surface, the male vegetative cell differentiates into the pollen tube that delivers the sperm to the ovule, whereas, after fertilization, the female central cell forms the basis of the triploid endosperm, which supports the developing next generation." http://www.sciencedirect.com/science/article/pii/S1534580713000427 View in LinkedIn

THE WHY. "You may ask why plants even bother with such an odd and complicated life cycle. First, going through a haploid-only stage allows for the weeding out or removal of bad genes. Second, going through a diploid stage allows for genetic variation. Both of these help improve the overall survival of the plant species." Thirdly, it allows the zygote to be dormant until favorable conditions occur. http://study.com/academy/lesson/alternation-of-generations-the-gametophyte-and-sporophyte.html View in LinkedIn

BIG IMPACT SYSTEM. "If you have an alien species or fantasy race and you want to give them a funky reproductive characteristic (that could easily have massive effects on the development of their society), alternation of generations could be one way to go." https://www.reddit.com/r/worldbuilding/comments/3iq3xw/worldbuilding_biology_lesson_alternation_of/ View in LinkedIn

SPOROPHYTE DOMINANCE POPULAR. “95% of all plants have a dominant sporophyte generation in their life cycle. Pollen, produced by the sporophyte, allowed seed plants to adapt to dry land.” https://lnkd.in/dGN5WNg View in LinkedIn

VASCULAR PLANTS. “Bryophytes have gametophyte-dominated life cycles; seedless vascular plants have sporophyte-dominated life cycles; seed plants have very protected gametophytes that obtain their nutrition from their parents, and are even more reduced than seedless vascular plants; whereas gametophytes from seedless vascular plants are free living and have to fend for themselves.” https://lnkd.in/dGN5WNg View in LinkedIn

SO ENDS this snippet into the complicated reproductive strategies of plants. Plants evolved from aquatic single celled algae, and transitioned onto dry land, where sperm needed protection against drying during dispersal, and thus pollen was born. Dry land was also a harsher environment, so a quiescent protected stage in the life cycle was born. And even within plants as a group, enormous reproductive variation is seen. View in LinkedIn