Genome-wide identification and expression analysis of U-box gene family in Juglans regia L.

The knowledge of transcription factor (TF) families is an important aspect in the post-genomic era. The U-box TF play pivotal role in plant development and growth. Although, the U-box gene family has been extensively investigated in many plants, it has not been systematically explored in Juglans regia. This study aims to identify U-box TF in J. regia genome and explore their gene expression and evolutionary relationship. A sum of 88 candidate JrU-box genes were identified in the Juglans database and classified into 10 groups. These JrU-box genes were unevenly distributed on J. regia's 16 chromosomes, with three chromosomes duplicated as tandem repeats, indicating an expansion of the similar to Arabidopsis thaliana. Motif composition and conserved domain analysis showed that the JrU-box genes contain two conserved motifs (1 and 2) and three conserved protein domains (U-box, RING U-box, and Zf-RING U-box), respectively. In addition, the structural analysis showed that most JrU-box genes have one exon and 12 introns. The determined JrU-box gene expression profiles indicated their potential involvement in various developmental and physiological processes. Specifically, 33 JrU-box genes were highly expressed in reproductive tissues (female flower, male flowers, and fruit) of J. regia, whereas, other identified genes were highly expressed in vegetative tissues, suggesting that the JrU-box gene family plays a role in flower development. Hence, we can expect that JrU-box gene family may play a major role in J. regia overall development.