Submission Type
Poster
Abstract
Mutations are the ultimate source of genetic variation, and it is commonly assumed that mutations are always harmful when they affect an organism's survival and reproduction. However, previous research in Arabidopsis thaliana has shown the opposite of this, and suggests that up to half of mutations may be beneficial. One hypothesis for this could be the role of somatic selection weeding out harmful mutations and elevating the presence of beneficial ones during growth before reproduction. We studied this effect by comparing early life fruits to late life fruits in second generation Arabidopsis thaliana. We observed these two stages because we expect late life fruits tend to go through more mitotic divisions in the meristem, and have a higher chance of experiencing selection compared to early life fruits. We are attempting to enhance our ability to see this outcome by using two homozygous SALK TDNA mutants: (1) increased mutation rate and (2) increased meristem size. Due to the rarity of mutations, increasing the mutation rate will give us greater power to detect this effect. Similarly, a larger meristem population size should increase the efficiency of natural selection. Though we hypothesized that late life progeny would have greater fitness (more fruits than early in life, we found no significant difference. This could be a result of other mechanisms counteracting the power of somatic selection, resulting in a lack of detectable differences in fitness. For example, Muller’s ratchet would predict an increasing number of mutations and decreased fitness with age. Similarly, variation across lifespan in resource allocation might also interfere with our ability to detect somatic selection.
Somatic Selection and Mutation in Arabidopsis thaliana
Mutations are the ultimate source of genetic variation, and it is commonly assumed that mutations are always harmful when they affect an organism's survival and reproduction. However, previous research in Arabidopsis thaliana has shown the opposite of this, and suggests that up to half of mutations may be beneficial. One hypothesis for this could be the role of somatic selection weeding out harmful mutations and elevating the presence of beneficial ones during growth before reproduction. We studied this effect by comparing early life fruits to late life fruits in second generation Arabidopsis thaliana. We observed these two stages because we expect late life fruits tend to go through more mitotic divisions in the meristem, and have a higher chance of experiencing selection compared to early life fruits. We are attempting to enhance our ability to see this outcome by using two homozygous SALK TDNA mutants: (1) increased mutation rate and (2) increased meristem size. Due to the rarity of mutations, increasing the mutation rate will give us greater power to detect this effect. Similarly, a larger meristem population size should increase the efficiency of natural selection. Though we hypothesized that late life progeny would have greater fitness (more fruits than early in life, we found no significant difference. This could be a result of other mechanisms counteracting the power of somatic selection, resulting in a lack of detectable differences in fitness. For example, Muller’s ratchet would predict an increasing number of mutations and decreased fitness with age. Similarly, variation across lifespan in resource allocation might also interfere with our ability to detect somatic selection.
Comments
Angie Roles, Oberlin College