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Abstract Detail



Molecular Ecology and Evolution

Cruzan, Mitchell B [1].

Why plants evolve faster (than animals).

Mutation accumulation in plants differs from organisms with separate germlines in a number of ways.  First, the potential for accumulation of genetic mutations and epigenetic modifications is much greater in plants because of extensive somatic growth intervening between zygotes and the formation of gametes.  The large number of mitotic divisions occurring during vegetative growth generates a large mutational load that may depress the fitness of inbred offspring.  Inbreeding Depression can be particularly severe after autogamous pollinations because of mutations that accumulated during the growth of each stem.  Second, somatic mutational load may be alleviated, and beneficial mutations retained, by cell lineage selection.  The effects of selection in populations of cell lineages contributing to vegetative growth may be responsible for the observation of relatively high frequencies of beneficial mutations in plants and diploid unicellular organisms.  Competition among mitotically dividing lineages of cells constitutes an intra-generation level of selection that could reduce genetic load and accelerate adaptive responses to challenging environmental conditions.  Third, the exposure of mutations to selection during pollen growth has the potential to provide an additional episode of intra-generation selection.  The effects of Gametophytic Selection have much more potential to purge deleterious variation because mutations are expressed in the haploid state so they are not masked by dominant alleles.  Expressed lethal mutations will probably be eliminated during pollen development (i.e., affecting pollen viability as described above for aspens), pollen germination, and pollen tube growth, and the much of the deleterious mutational load is likely to be filtered out by competition among pollen prior to fertilization.  The effects of extensive somatic growth and intra-generation selection have the potential to alter the process of mutation accumulation in plants by removing deleterious mutation and favoring the retention of beneficial changes. Lack of a separate germline and inclusion of post-meitotic transcription in the gametophyte may increase the incidence and filtering of mutations.  The separation of germlines in metazoans provides for reliable transmission of genetic information that is unadulterated by the vagaries of genetic and epigenetic alterations that accrue during somatic growth.  The reason for the contrast in germline transmission between plants and animals remains unresolved, but may be due to much greater sensitivities to gene dosage imbalances during animal development.  Plants, on the other hand, may benefit from the combination of somatic mutation accumulation and intra-generation selection as a consequence of their extensive vegetative growth and sedentary life style.


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1 - Portland State University, Department Of Biology, PO BOX 751, PORTLAND, OR, 97207, USA

Keywords:
Weismann Barrie
gametic selection
Cell Lineage Selection
Mutation Accumulation
Germline.

Presentation Type: Oral Paper:Papers for Topics
Session: 11
Location: Firs North/Boise Centre
Date: Monday, July 28th, 2014
Time: 1:30 PM
Number: 11001
Abstract ID:830
Candidate for Awards:None


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