Deleterious Mutation Accumulation in Arabidopsis thaliana Pollen Genes: A Role for a Recent Relaxation of Selection.

In many studies, sex-related genes have been found to evolve rapidly. We therefore expect plant pollen genes to evolve faster than sporophytic genes. In addition, pollen genes are expressed as haploids which can itself facilitate rapid evolution because recessive advantageous and deleterious alleles are not masked by dominant alleles.

The 5'-untranslated region of the ntp303 gene strongly enhances translation during pollen tube growth, but not during pollen maturation.

Transcripts of the ntp303 gene accumulate abundantly throughout pollen development, whereas the protein only accumulates to detectable levels after pollen germination. In an attempt to explain the divergence in the accumulation profiles of the mRNA and the protein, we investigated the role of the untranslated regions (UTRs) in enhancing ntp303 translation during the transition from developing to germinating pollen. Luciferase reporter gene fusion constructs containing the ntp303 5'-UTR gave rise to luciferase activity that was up to 60-fold higher during pollen tube growth than that of constructs containing different 5'-UTRs.