Saturday, 26 May 2012

Plants Cloned as Seeds: A Step Towards Artificial Apomixis


Once upon a time, plant breeders have envisioned the potential of apomixis but it still seemed to be so far away. Recent findings in agricultural science, however, showed that it is starting to come within our reach. As said by Simon Chan, assistant professor of plant biology at UC Davis, “plants have for the first time been cloned as seeds... a major step towards making hybrid crop plants that can retain favorable traits from generation to generation”.

Plants such as dandelions and hawkeed can produce seeds that are exact genetic replicas of their parent without having to go through recombination that occurs during sexual reproduction- an asexual type of reproduction that is more commonly referred to as apomixis. Magically as it seems, not many plants have this trait.

“The new discovery gets to the same result as apomixis, although by a different route,” said Chan.

In their study in 2010, he and his colleagues demonstrated that they could produce Arabidopsis thaliana that contained only sets of genes from one parent. The whole process was done by crossing a plant with engineered strain that carried a modified version of CENH3- a gene in the centromere that is responsible for correct chromosome segregation- with the mutant MiMe that produces diploid clonal gametes.

After fertilisation, in up to third of the progeny (34%) produced, the chromosomes carrying the modified CENH3 were eliminated, yielding diploid seeds that were genetically identical (i.e. clones) to one of the parents. At last, we are now able to suppress the natural recombination of genomes that occurs during sexual reproduction.

Sadly, this technique does not fully recapitulate apomixis as it still involves fertilisation between two plants. But a possible way to deal this requirement is to generate plants that produce either mutant MiMe or dyad proteins and the genetically engineered CENH3 gene in their reproductive tissues.

If we could apply this technique in major food crops such as lettuce and tomato, we would be able to suppress the natural recombination of their genomes that occurs during sexual reproduction. Thus, beneficial traits such herbicides and frost resistance, insect infestation tolerance as well as better nutritive content could be maintained with no loss of hybrid vigour through successive generations. The cost of crop production would also be greatly minimised when using this technique.

Cloning plants through seeds is indeed a potent tool to propagate cultivars that can retain their original genetics through generations. In a decade or two, if not in a few years, this technique could profoundly change the way essential food crops are produced today, and this could as well be the future of agriculture.

References
1.      University of California- Davis 2011, Plants cloned as seeds: Hybrids that breed true would be a major advance for crop plants, ScienceDaily, viewed 13 February 2012, <http://www.sciencedaily.com/releases/2011/02/110217141315.htm>.
2.      Reece, JB, Meyers, N, Urry, LA, Cain, ML, Wasserman, SA, Minorsky, PV, Jackson, RB & Cooke, BN 2012, ‘Exploring Fruit and Seed Dispersal’, Campbell Biology, 9th ed., Pearson Australia Group, pp. 832-838.
3.      Marimuthu, MPA, Jolivet, S, Ravi, M, Pereira, L, Davda, JN, Cromer, L, Wang, L, Nodue, F, Chan, SWL, Siddiqi, I & Mercier, R 2011, ‘Synthetic Clonal Reproduction Through Seeds’, Science, viewed 13 March 2012, <http://www.sciencemag.org/content/331/6019/876>.
4.      Ravi, M & Chan, SWL 2010, ‘Hapoloid plants produced by centromere-mediated genome elimintation’, Nature, 484, viewed 17 March 2012, <http://www.nature.com/nature/journal/v464/n7288/full/nature08842.html>.
5.      Ledford, H 2011, Genetic engineering brings cloned crops closer, Nature Publishing Group, viewed  13 March 2012, <http://www.nature.com/news/2011/110217/full/news.2011.102.html>.
6.      Bicknell, RA & Koltunow 2004, ‘Understanding Apomixis: Recent Advances and Remaining Conundrums’, The Plant Cell, viewed 17 March 2012, <http://www.plantcell.org/content/16/suppl_1/S228>.
7.      Jolivet, S, d’Erfurth, I, Froger, N, Catrice, O, Novatchkova, M & Mercier, R 2009, ‘Turning Meiosis into Mitosis’, PLoS Biol, viewd 17 March 2012, <http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1000124>.
8.      Mosquin, D 2010, Arabidopsis thaliana, viewed 18 March 2012, <http://www.botanicalgarden.ubc.ca/potd/2010/03/arabidopsis_thaliana_4.php>
9.      Chan, SWL 2011, Chan Lab, viewed 18 March 2012, <http://chan.openwetware.org/Research.html>

1 comment:

  1. This blog tells us about some thing new regarding artificial apomixis .Really great post with important information.I really like this effort.Thanks for sharing this!!!

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