Abstract
The recently proposed omnigenic model makes use of network theory to distinguish central (or core) from peripheral genes underlying phenotypes. Core genes are typically few, they marginally contribute highly but altogether explain only a small part of trait heritability, while peripheral genes, each of small influence, are so numerous that they finally lead risk. In order to test this model, we collected and sequenced RNA from 459 European black poplars. We built the coexpression networks to define core and peripheral genes as the most and least connected ones. We computed the role of each of these gene sets in the prediction of phenotypes, with a linear additive model and an interactive neural network model. These analyses showed that core genes act directly and contribute additively to phenotypes, consistent with a downstream position in a biological cascade. Oppositely, peripheral genes interact to influence phenotypes, consistent with an upstream position. Overall, our work is the first empirical proof that omnigenic holds in trees, providing one step further towards the universalization of this model.