A high-quality walnut genome assembly reveals extensive gene expression divergences after whole-genome duplication.

The common walnut Juglans regia and its related species in the genus Juglans are important economic trees, which have been widely grown for nut and wood productions in many counties. In the Juglans genus, there are ~21 diploid species all with 2n=32 chromosomes, which can be divided into four major sections based on phylogenetic analyses and fruit morphology - Cardiocaryon (e.g., J. cathayensis and J. mandshurica), Juglans (e.g., J. sigillata and the most popular one J. regia), Trachycaryon (e.g. J. cinerea) and Rhysocaryon (e.g., J. hindsii, J. nigra, and J. microcarpa) (Aradhya et al., 2017). For walnuts, the draft genome sequences of several Juglans species had been generated from second-generation sequencing platform (J. regia Chandler N50: 465Kb, Martınez-Garcıa et al., 2016; J. regia Chandler N50: 640Kb, Stevens et al., 2018).