Genome-Wide Identification and Analysis of the BBX Gene Family and Its Role in Carotenoid Biosynthesis in Wolfberry (Lycium barbarum L.)

Abstract

The B-box proteins (BBXs) are a family of zinc-finger transcription factors with one/two B-Box domain(s) and play important roles in plant growth and development as well as stress responses. Wolfberry (<i>Lycium barbarum</i> L.) is an important traditional medicinal and food supplement in China, and its genome has recently been released. However, comprehensive studies of <i>BBX</i> genes in <i>Lycium</i> species are lacking. In this study, 28 <i>LbaBBX</i> genes were identified and classified into five clades by a phylogeny analysis with BBX proteins from <i>Arabidopsis thaliana</i> and the <i>LbaBBXs</i> have similar protein motifs and gene structures. Promoter <i>cis</i>-regulatory element prediction revealed that <i>LbaBBXs</i> might be highly responsive to light, phytohormone, and stress conditions. A synteny analysis indicated that 23, 20, 8, and 5 <i>LbaBBX</i> genes were orthologous to <i>Solanum lycopersicum</i>, <i>Solanum melongena</i>, <i>Capsicum annuum</i>, and <i>Arabidopsis thaliana</i>, respectively. The gene pairs encoding LbaBBX proteins evolved under strong purifying selection. In addition, the carotenoid content and expression patterns of selected <i>LbaBBX</i> genes were analyzed. <i>LbaBBX2</i> and <i>LbaBBX4</i> might play key roles in the regulation of zeaxanthin and antheraxanthin biosynthesis. Overall, this study improves our understanding of <i>LbaBBX</i> gene family characteristics and identifies genes involved in the regulation of carotenoid biosynthesis in wolfberry.