Download File

Ryan Bird
Biology Lab 1615
Turning Meiosis into Mitosis Article Summary
The article “Turning Meiosis into Mitosis” was published June 9, 2009, this article was
written based on the experimentation of Isadee d'Erfurth, Sylvie Jolivet, Nicole Froger, Olivier
Catrice, Maria Novatchkova, and Raphael Mericer. These scientists did research on the processes
of meiosis and how mutations of genes can alter the meiotic process. They used the sexual plant
Arabidopsis thaliana to do their research. The scientists wanted to study how altering the process
of apomixis (asexual clonal reproduction through seeds) can result in apomeiosis (a deregulation
of meiosis that results in a mitotic-like division). By doing this they hoped that the process of
meiosis would be totally replaced by mitosis.
Through apomeiosis all the parent's genetic information is retained in the gamete. During
the study the scientists identified a gene that controls one of the three features of meiosis. The
scientists stated that by combining a mutation in this gene with two other mutations, one would
eliminate recombination and pairing, and another would modify chromatid segregation. Because
this gene was identified they created a genotype which meiosis is totally replaced by mitosis
without affecting subsequent sexual processes.
The scientists used a gene At3g57860 which the renamed OSD1, for omission of second
division. They investigated the role of the OSD1 gene by isolating and characterizing two
mutants, osd1-1 and osd1-2. The testing of these two mutations showed that they were allelic,
but both independent mutants produced dyads in meiosis. As stated in the article the osd1
mutants did not show any somatic development defects, male and female gametophyte lethality,
or reduced fertility thus far. Their experiments with these osd1 mutants demonstrated that they
produce high levels of male (100%) and female (85%) diploid spores, resulting in functional
gametes. The scientists believed that the dyad production was due to the absence of the second
meiotic division. They tested this by taking advantage of the two different genetic backgrounds
of osd1-1 and osd1-2 mutants. All the diploid gametes tested had the predicted genetic
characteristics. These results confirmed that the absence of a second meiotic division was the
cause of the 2n gametes production in osd1. The scientists called the new genotype MiMe for
mitosis instead of meiosis. Other tests showed that the MiMe plants were systematically
tetraploid (n=24), this confirms that the mitotic-like division gives rise to functional diploid
gametes.
The scientists were able through the osd1 mutant gene to create a MiMe plant which can
produce viable diploid male and female gametophytes. In successive generation the ploidy is
expected to double, this is due to the replacement of meiosis with mitosis. Through further
experimentation the scientists obtained tetraploid and octoploid. However, with the increase in
ploidy level there is a decrease in fertility; further research will need to be done to find the cause
of this.
The article explains in detail the process of apomixis, which is separated into three
developmental components. An absence or alteration of meiosis which prevents reduction
(apomeiosis), the fertilization-indpendent development of the embryo from the egg cell
(parthenogenesis), and the initiation of endosperm development with or without fertilization.
This information shows that penetrant apomeiosis can be induced in a sexual plant, when a
mitotic-like division replaces meiosis in the MiMe genotype. Due to the high level of viability of
MiMe plants, in contrast to apomixis engineering alone, the scientists hope to find other sexual
plant species to research. They believe that the results of this experiment suggest that it should be
possible to introduce apomixis into sexual plant species as was done in Arabidopis plants in this
experiment.