Divergence of expression variability following gene and genome duplication in Arabidopsis thaliana

Genome analyses have revealed that gene duplication in plants is pervasive, providing a primary source for the emergence of new genes. The population genetic mechanisms governing the preservation of new gene, especially in the critical very initial phase, have remained largely unknown. New genes may arise through small-scale duplication, or large-scale duplication such as polyploidy. Patterns of divergence between duplicated genes may vary, leading to functional bias in gene retention among these modes. For example, genes arising from tandem duplications tend to be involved in environmental responses. Gene expression divergence may play an important role in the preservation of duplicated genes, which has recently been observed to differ markedly between large- and small-scale duplication events. But the exact causal relationship has not established. Here, to better understand the mechanisms of expression divergence and their role in promoting gene retention, we study a frequently overlooked aspect of gene expression - expression variability - as measured by within-line expression variation. We found that duplicates tend to exhibit higher expression variability than singletons. This is likely driven by induction of high expression variability immediately after small-scale duplication events and prolonged evolutionary processes following large-scale duplications.  These findings suggest a potential overarching mechanism facilitating gene expression divergence and, consequently, promoting gene retention.