Genome-wide analyses and expression patterns under abiotic stress of LAC gene family in pear (Pyrus bretschneideri)

Abstract

Plant laccases are copper-containing glycoproteins oxidizing monolignol, which is a key regulator for lignin polymerization and deposition in plant cell walls. In plants, the LAC gene family has been identified and functionally characterized in Arabidopsis, rice, and other plant species. Whereas, no systematic analysis of LAC genes was explored in pear (Pyrus bretschneideri), especially their biological roles in stress responses. In this study, a total of 40 P. bretschneideri LACs (PbLACs) were identified from the pear genome, among which 32 PbLACs members were distributed on 14 chromosomes, and 8 PbLACs were mapped onto scaffold contigs. Subsequently, the chromosome localizations, gene structures, conserved domains, gene duplication were analyzed comprehensively and bioinformatically. Phylogenetic analysis demonstrated that the PbLACs were classified into seven groups. Synteny analysis exhibited that whole-genome duplication (WGD)/segmental duplication was essential for the expansion of PbLAC family. In detail, the 26 PbLACs duplicated gene pairs were taken place at the two WGD events. Further, our results showed that purifying selection presented as the primary force to drive the evolution of PbLACs. Notably, the transcriptomic data were used for exploring the biological roles of PbLACs in response to abiotic stresses (cold, drought, and salt) in pear. We found that the expression of certain PbLACs was significantly induced by drought, cold or salt treatments, suggesting that these PbLACs are potentially key genes for further functional characterization in pear in the future. Taken together, our results not only contribute to an enhanced understanding of the evolutional complexity of PbLAC gene family but also provide a good platform for functional studies of PbLAC genes in response to various abiotic stresses.