Plant & zo
The science of plants and more
Arrested development
Plants procreate through a double fertilization. They don’t get twins, only one of the two sperm cells fertilizes an egg cell. The second sperm cell is needed for the fertilization of the central cell. To form the endosperm, tissue that supports the developing embryo in its growth and germination. Giving the endosperm an important task. But sometimes it fails to execute that task. Like for example when it is formed from two species with a different genome number. Then embryo development arrests. Researchers from Sweden and Germany found out why.
After fertilization endosperm develops through first undergoing lots of nuclear divisions without the following cell division. Only after getting the desired number of nuclei, the cellularization will start. But not if the parents of the endosperm do not have the same number of genomes. With as result that also embryo development stops.
With a little ABA researchers can help the endosperm
To study what precisely causes the endosperm not to cellularize, the researchers analysed which genes were expressed in the endosperm. They discovered that especially genes for making, processing, and reaction to the drought stress manager behaved differently. With as result; there was more ABA present in the endosperm when its parents did not have an equal number of genomes.
Now the big question was why there was more ABA. Was it the cause that the cellularization did not start, or was the endosperm trying to safe embryo development? When the researchers inhibited the breakdown of ABA, then they saw more seeds with parents that do not have an equal number of genomes survive. But when they switched off the synthesis of ABA, then less seeds with parents that do not have an equal number of genomes survived. The confirmation that ABA was needed to survive came when the researchers grew the seeds parents that do not have an equal number of genomes on growth medium. With extra ABA in the medium more seeds survived.
Endosperm is doing all it can to safe embryo development. With a little extra ABA researchers can help seeds with parents that do not have an equal number of genomes to develop correctly. Now this is known it means in practice; that we can support the seeds out crosses from plants that do not have an equal number of genomes, and hopefully develop new plants.
Literature
Wenjia Xu, Hikaru Sato, Heinrich Bente, Juan Santos-González, Claudia Köhler (2022) Endosperm cellularization failure induces a dehydration stress response leading to embryo arrest. The Plant Cell, koac337, https://doi.org/10.1093/plcell/koac337
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