Nov 5, 2018

How does genome size affect the evolution of pollen tube growth rate, a haploid performance trait?

BioRxiv : the Preprint Server for Biology
John Brandon Reese, Joseph Williams

Abstract

Male gametophytes of most seed plants deliver sperm to eggs via a pollen tube. Pollen tube growth rates (PTGRs) of angiosperms are exceptionally rapid, a pattern attributed to more effective haploid selection under stronger pollen competition. Paradoxically, whole genome duplication (WGD) has been common in angiosperms but rare in gymnosperms. Pollen tube polyploidy should initially accelerate PTGR because increased heterozygosity and gene dosage should increase metabolic rates, however polyploidy should also independently increase tube cell size, causing more work which should decelerate growth. We asked how genome size changes have affected the evolution of seed plant PTGRs. We assembled a phylogenetic tree of 451 species with known PTGRs. We then used comparative phylogenetic methods to detect effects of neo-polyploidy (within-genus origins), DNA content, and WGD history on PTGR, and correlated evolution of PTGR and DNA content. Gymnosperms had significantly higher DNA content and slower PTGR optima than angiosperms, and their PTGR and DNA content were negatively correlated. For angiosperms, 89% of model weight favored Ornstein-Uhlenbeck models with a faster PTGR optimum for neo-polyploids, but PTGR and DNA content were not ...Continue Reading

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Mentioned in this Paper

Study
Gametophytes
Size
Genome
Genes
Sperm Cell
Genome Assembly Sequence
Phylogenetic Analysis
Pollen Tube
Haploid Cell

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