Functional Characterization of Duplication-Resistant Genes

Massive gene loss after whole genome duplication is considered to be largely random, making non-random gene loss an interesting evolutionary question. While genes preferentially retained in duplicate are well studied, ‘Duplication Resistant’ (DR) genes, which are restored to single copies in a variety of plant genomes after multiple shared or independent whole genome duplication events are underexplored. Bioinformatic studies show that they are structurally and functionally distinctive, but are not sufficient to explain the basis of their copy number regulation. Here, we summarize large scale functional characterization of DR gene mutants of Arabidopsis thaliana. T-DNA Knockout lines for more than 160 Arabidopsis candidate DR genes have been screened under standard lab conditions as well as about ten stressed conditions, resulting in discovery of new phenotypes for about 25 genes. Mutants overexpressing DR genes, though with limited penetrance, show a relatively high percentage of reduced fertility phenotype for soil grown plants. In all, the high percentage of knockout phenotypes as well as fitness-defective overexpression phenotypes provides new insight into why plant cannot afford either to lose the only copy, or to keep many copies, of DR genes. Genes with obvious phenotypes for their knockout mutants usually do not have phenotypes for their overexpression mutants, or vise versa , perhaps indicating that dosage balance insensitivity might not be a major reason for loss of duplicated copies of these genes.