Month: September 2022

SPERM COMPETITION. “In vertebrate and invertebrate species millions of sperm cells compete for fertilization with the ova or egg cell. Usually the largest, longest, fastest and physiologically most active sperm cells win the race and defective sperm cells are sorted out. Sperm competition thus represents a powerful selective force to guarantee fertilization and reproductive success.” https://lnkd.in/dhgWbCC View in LinkedIn

DIFFERENT SPERM COMPETITION. “Sperm competition does not occur in flowering plants as typically only a single pair of sperm cells is delivered for double fertilization. Two recent reports show that plants are capable of avoiding reproductive failure when defective sperm cells are released.” http://www.sciencedirect.com/science/article/pii/S096098221200468X View in LinkedIn

RACING POLLEN TUBES. “The reproductive strategy of flowering plants is different and involves competition among growing pollen tubes to enter one ovule and to deliver their sperm cell cargo. The first pollen tube that enters an ovule usually releases its cargo and one sperm cell fuses with the egg cell forming the embryo while the second sperm cell fertilizes the central cell to generate the endosperm. Later-arriving pollen tubes do not enter already targeted ovules.” http://www.sciencedirect.com/science/article/pii/S096098221200468X View in LinkedIn

NUTS AND BOLTS. “In flowering plants, the egg is intimately associated with typically six to eight other haploid cells forming the female gametophyte. These include the central cell representing the second female gamete and two synergid cells that produce the signals, which guide the male gametophyte, or pollen tube, towards the ovule. The pollen tube delivers two non-motile sperm cells whose release occurs by bursting, which in turn is triggered when the tube interacts with the synergid cells.” https://lnkd.in/dXVTT6X View in LinkedIn

TWO PRODUCTS. “The receptive synergid cell degenerates following this interaction, whereas the other synergid cell persists. After their ejection from the pollen tube, the two sperm cells stay immobile between the two female gametes for several minutes and subsequently fuse with the egg and central cells, respectively. These two fusion events give rise to the embryo and to the endosperm, respectively, and the process is therefore termed double fertilization.” http://www.nature.com/articles/ncomms5722?WT.ec_id=NCOMMS-20140829 View in LinkedIn

CONSTANT CROSS-TALK. “During its journey, the angiosperm pollen tube communicates with its environment, allowing the maternal reproductive tissues to recognize and support compatible pollen in order to avoid fertilization failure. The acceptance of compatible pollen and the subsequent steps leading to successful fertilization comprise complex and cooperative processes between the pollen and the receptive pistil.” http://www.sciencedirect.com/science/article/pii/S1674205214608996 View in LinkedIn

DISCRIMINATION. “During the various phases of pollination...angiosperms distinguish self from non-self-pollen and direct and control pollen tube growth through the maternal tissues towards the egg apparatus.” http://www.sciencedirect.com/science/article/pii/S1674205214608996 View in LinkedIn

RUNNING THE GAUNTLET. “During this journey, the pollen tube of Arabidopsis, for example, interacts with at least seven different pistil cell types prior to arrival at its final destination inside the ovule. To add complexity, further layers of recognition exist. These include self-recognition and specialized processes to prevent self-fertilization and consequent inbreeding, as well as interspecific barriers, which are poorly understood at the molecular/cellular level.” http://www.sciencedirect.com/science/article/pii/S1674205214608996 View in LinkedIn

SO ENDS this first weekend on double fertilization in flowering plants. After millennia of random experimentation and brutal winnowing, the reproductive pieces that survived in this group look more like a functional train crash rather than an elegant and streamlined process of passing on genes and generating diversity by outbreeding. This is a poster child of evolution as a blind band-aid process where incompatible systems are bolted together after lineage fusions in a make-do manner. And still, they somehow work against all odds. View in LinkedIn

PROVOCATIVE QUESTION. “We came to wonder if there can be some kind of convergence between human viruses and computer viruses...It may sound like a scenario for a bad Hollywood movie, but it is not such a stupid question." https://lnkd.in/ddTvp9R View in LinkedIn