2013-05-05 12:25:06
These studies reveal the importance of keeping teams of genes together
One day in the 1930s, a ship from South America docked in the port of Mobile, Alabama, USA. In addition to the crew, the ship was carrying stowaways: a colony of red ants of the species Solenopsis invicta, which, of course, were also happy to touch land. Since that day, this species of ant has become a pest in the southern United States. Other similar trips have taken her to Australia, China, Thailand, Taiwan and the Philippines. Very aggressive, S. Invicta competes successfully with other ant species, and its anthills are very damaging to some crops.
However, if it were not for this landing, today we would know less about science. The study of these very interesting insects is proving to be most fruitful for understanding many mysteries of evolution, including the evolution of social interaction and the evolution of sex chromosomes. Let’s see why.
MONARCHY OR OLIGARCHY
Interestingly, the ant S. invicta adopts two forms of social colonies: the first with only one queen (called monogynes), and the second with multiple queens (called polygynes). A few years ago it was discovered that this different behavior was associated with genetic variation at a single site, or locus, on one of its chromosomes. This locus contained a gene, called Gp-9, that produces an olfactory receptor. Apparently, the quality of the smell that the workers detect prevents them from tolerating more than one queen – they kill the others – in one case, but allows them to tolerate several in the other. For these ants, monarchy or oligarchy is just a matter of smell although, in both cases, the true power is held by the workers.
But, as always in science, there is usually much more behind what we smell. Other studies demonstrated that the monogyny or polygyny of S. invicta colonies depends on the presence or absence in its genome of two identical copies of the Gp-9 gene in its pairs of chromosomes. There are two variants of this gene, called B and b. Ants that have two chromosomes with the same B variant (which we will call BB) form colonies with a queen. On the contrary, ants that have a variant B and another b (which we will call Bb) form colonies with several queens. However, and this is to take the breath away from curiosity, these latter ant colonies only accept multiple queens if they are of the same type, that is, type Bb. If by chance a queen of type BB tried to usurp the power of that colony, she would not be able to, since the workers would detect her by her smell and kill her with her terrible stingers.
But. What happens to type bb ants? Well, these ants are nonviable, that is, they die at some point during their development, so there are no bb queens or bb workers.
SEX AND SOCIETY
Researchers were, however, reluctant to grant so much power to a single gene. Recent studies, published in the journal Nature, reveal, in fact, that these differences in social behavior, although they are inherited as if they resided in a single gene, in fact reside in a large chromosomal region that contains hundreds of genes, and that, by mechanisms Complex genetic mechanisms that prevent the mixing – the recombination – of similar DNA regions between the chromosomes of the same pair, are inherited as if it were a single gene.
These genetic characteristics give this chromosomal region of the ant genome some interesting properties. First, they convert region B into a genetic region that promotes cooperation between queens that possess only one copy of this variant, but not both. The BB workers kill all but one of the BB queens, and the Bb ants also kill the BB queens, so cooperation between BB queens is not possible. It is only between Bb queens.
Secondly, it is interesting to see that this chromosomal region of S. invicta functions in a similar way to sex chromosomes. In general, female animals have two copies of the X chromosome (XX, similar to BB colonies), but males have one X and one Y chromosome (XY, similar to Bb colonies). Bb colonies are not viable, nor are YY individuals.
This similarity, together with the different behavior and reproductive function of males and females, and the different social and cooperative behavior of both types of ant colonies, reveals the importance of the genetic mechanisms by which species can maintain together, in a same chromosome or in a region of one of them, to many genes that participate together in the generation of sex, in our case, or in a different social behavior, in the case of ants, and perhaps also participate in other biological phenomena yet to be determined. In any case, it remains to be revealed why it is so important for S. invicta to have this genetic mechanism for controlling social behavior, as it is also necessary to reveal how sexual differentiation began its steps during evolution to provide us with as many delights and disappointments as we can. provides sex today.
WORKS BY JORGE LABORDA.
One Moon, one civilization. Why the Moon tells us that we are alone in the Universe
One Moon one civilization why the Moon tells us we are alone in the universe
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#Cienciaes.com #red #queens #talk #sex