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Abstract Insights into changes in genome base composition underlying crop domestication can be gained by using comparative genomics. With this approach, previous studies have reported that crop genomes during domestication accumulate more nucleotides adenine (A) and thymine (T) (termed as AT‐increase) across polymorphic sites. However, the potential influence of the environment or its factors, for example, solar ultraviolet (UV) radiation and temperature, on the AT‐increase has not been well elucidated. Here, we investigated the AT‐increase in barley ( Hordeum vulgare L.) and rice ( Oryza sativa L.) and the association with natural environments, where accessions are distributed. With 12,798,376 and 2,861,535 single‐nucleotide polymorphisms from 368 barley and 1375 rice accessions, respectively, we discovered that AT increases from wild accessions to improved cultivars, and genomic regions with larger AT‐increase tend to have higher UV‐related motif frequencies, suggesting solar UV radiation as a potential factor in driving genome variation. To link AT change with the geographic distribution, we gathered georeferenced accessions and examined their local environments. Interestingly, negative correlations between AT and environmental factors were observed ( r = −0.39 ∼ −0.75) and modern accessions with higher AT values, as compared with wild relatives, are from the environments with lower solar UV radiation or lower temperature. With AT and environmental factors as phenotypes, genome‐wide association mapping identified three candidate genes that have the potential to contribute to AT variation under the effect of environmental conditions. Our findings provide genomic and environmental insights into evolutionary pattern of DNA base composition and underlying mechanisms.
Gou et al. (Tue,) studied this question.