Pan-phylum Investigation Of Meiotic Gene Conversions

Meiotic gene conversion disturbs linkage disequilibrium,potentially affecting the ability to detect causative variants,while a GC-favouring conversion bias enables fixation of deleterious alleles,disturbs tests of natural selection,and potentially explains commonly reported correlations between G+C content and recombination rate.However,the importance of these effects depends on the rates of gene conversion and the magnitude of biases,both of which are currently poorly resolved as direct analyses are technically challenging.To estimate diversity in rates and biases here we report results of whole-genome sequencing of all tetrad products in Saccharomyces,Neurospora,Chlamydomonas and Arabidopsis.The proportion of polymorphic markers converted varies over three orders of magnitude between species,with 2%of markers converted in yeast but only?0.005%in the two plant species.While,as expected,some of this variation is owing to differences in recombination rates,partially owing to chromosome number differences,we also observe an order of magnitude variation in median tract length.The latter is variable both between species and between crossover(CO)and non-crossover(NCO)conversion events.Indeed the two plant species have approximately the same net conversion rates but for different reasons.Despite three of the species showing a positive GC-recombination correlation,there is no significant net AT>GC conversion bias in any,despite high resolution in the two taxa(Saccharomyces and Neurospora)with relatively common gene conversion.We conclude that,for reasons other than variation in recombination rates,the impact of gene conversion varies markedly between species and there should be no presumption hat gene conversion is GC biased.In Neurospora exclusively we also detect sequence motifs associated with recombination events.