Genome-Wide Identification and Expression Analysis of NCED Gene Family in Pear and Its Response to Exogenous Gibberellin and Paclobutrazol.

The 9--epoxycarotenoid dioxygenase () is a key enzyme for the process of ABA synthesis that plays key roles in a variety of biological processes. In the current investigation, genome-wide identification and comprehensive analysis of the gene family in 'Kuerle Xiangli' ( Yu) were conducted using the pear genomic sequence. In total, nineteen members of genes were identified from the whole genome of pear, which are not evenly distributed over the scaffolds, and most of which were focussed in the chloroplasts. Sequence analysis of promoters showed many -regulatory elements, which presumably responded to phytohormones such as abscisic acid, auxin, etc. Synteny block indicated that the genes have experienced strong purifying selection. Multiple sequence alignment demonstrated that these members are highly similar and conserved. In addition, we found that genes were differentially expressed in various tissues, and three genes (, , and ) were differentially expressed in response to exogenous Gibberellin (GA) and Paclobutrazol (PP). and positively promote ABA synthesis in sepals after GA and PP treatment, whereas positively regulated ABA synthesis in ovaries after GA treatment, and positively regulated ABA synthesis in the ovaries after PP treatment. This study was the first genome-wide report of the pear gene family, which could improve our understanding of pear NCED proteins and provide a solid foundation for future cloning and functional analyses of this gene family. Meanwhile, our results also give a better understanding of the important genes and regulation pathways related to calyx abscission in 'Kuerle Xiangli'.