Gender-specific selection on codon usage in plant genomes.

Background: Currently, there is little data available regarding the role of gender-specific gene expression on synonymous codon usage (translational selection) in most organisms, and particularly plants. Using gender-specific EST libraries (with > 4000 ESTs) from Zea mays and Triticum aestivum, we assessed whether gender-specific gene expression per se and gender-specific gene expression level are associated with selection on codon usage.

Results: We found clear evidence of a greater bias in codon usage for genes expressed in female than in male organs and gametes, based on the variation in GC content at third codon positions and the frequency of species-preferred codons.

Male-biased transmission of deleterious mutations to the progeny in Arabidopsis thaliana.

The extent and cause of male-biased mutation rates, the higher number of mutations in sperm than in eggs, is currently an active and controversial subject. Recent evidence indicates that this male (sperm) bias not only occurs in animals but also in plants. The higher mutation rate in plant sperm was inferred from rates of evolution of neutral DNA regions, and the results were confined to the mitochondria and chloroplasts of gymnosperms.

Broad-scale analysis contradicts the theory that generation time affects molecular evolutionary rates in plants.

Several studies of plant taxa have concluded that generation time, including annual/perennial life history, may explain molecular evolutionary rate variation in selectively neutral DNA. Unlike in animals, there is little theoretical basis for why generation-time effects would exist in plants. Furthermore, previous reports fail to establish the generality of a generation-time effect in plants because of the small size of the datasets, a large proportion of which compared very widely divergent taxa differing in many characteristics other than generation time.

Male-driven evolution of mitochondrial and chloroplastidial DNA sequences in plants.

Although there is substantial evidence that, in animals, male-inherited neutral DNA evolves at a higher rate than female-inherited DNA, the relative evolutionary rate of male- versus female-inherited DNA has not been investigated in plants. We compared the substitution rates at neutral sites of maternally and paternally inherited organellar DNA in gymnosperms. The analysis provided substantial support for the presence of a higher evolutionary rate in both the mitochondrial and chloroplastidial DNA when the organelle was inherited paternally than when inherited maternally.