Genome-Wide Identification and Expression Analysis of CCO Gene Family in Liriodendron chinense

Abstract

Carotenoid cleavage oxygenase (CCO) is an enzyme that can catalyze carotenoids to volatile aromatic substances and participate in the biosynthesis of two important phytohormones, i.e., abscisic acid (ABA) and strigolactone (SL). However, the genome-wide identification and analysis of the <i>CCO</i> gene family in the rare and endangered woody plant <i>Liriodendron chinense</i> has not been reported. Here, we performed a genome-wide analysis of the <i>CCO</i> gene family in the <i>L. chinense</i> genome and examined its expression pattern during different developmental processes and in response to various abiotic stresses. A total of 10 <i>LcCCO</i> genes were identified and divided into 6 subfamilies according to the phylogenetic analysis. Subcellular localization prediction showed that most of the LcCCO proteins were located in the cytoplasm. Gene replication analysis showed that segmental and tandem duplication contributed to the expansion of this gene family in the <i>L. chinense</i> genome. <i>Cis</i>-element prediction showed that <i>cis</i>-elements related to plant hormones, stress and light response were widely distributed in the promoter regions of <i>LcCCO</i> genes. Gene expression profile analysis showed that <i>LcNCED3b</i> was extensively involved in somatic embryogenesis, especially the somatic embryo maturation, as well as in response to heat and cold stress in leaves. Furthermore, qRT-PCR analysis showed that <i>LcNCED3b</i> obviously responded to drought stress in roots and leaves. This study provides a comprehensive overview of the <i>LcCCO</i> gene family and a potential gene target for the optimization of the somatic embryogenesis system and resistance breeding in the valuable forest tree <i>L. chinense</i>.