Genome-wide identification and expression analysis of dirigent gene family in strawberry (Fragaria vesca) and functional characterization of FvDIR13

Dirigent proteins (DIR) are thought to have important roles in lignans or lignin-like molecules production, defensive responses, secondary metabolism, and disease resistance in plants. There is a lack of information about the DIR genes in strawberries (Fragaria vesca). In this study, 33 FvDIR genes were identified and divided into four subfamilies based on the phylogenetic analysis. A detailed bioinformatic analysis of FvDIR genes was performed including physiochemical properties of genes, chromosomal locations, exon-intron distribution, motif arrangements, in silico analysis of cis-elements, and protein localization. All the genes were unevenly distributed on 7 chromosomes. The structure and chromosomal distribution of FvDIR genes were systematically analyzed. Most of the genes showed conserved motif and domain composition within the same subfamily. According to exon-intron analysis, 85% of FvDIR genes have no intron. Evolutionary history analysis showed that tandem duplication (six sets) has played more roles in the expansion of gene family than segmental duplication (one set). In silico analysis of cis-elements suggested that most FvDIR genes may function in response to light, hormones, and environmental stresses. Furthermore, we analyzed the expression of FvDIR genes in different plants parts (roots, stolons, leaves, flowers, and fruits), against Colletotrichum gloeosporioides inoculation, and hormone (SA and JA) treatments. The majority of the genes displayed tissue-specific expression patterns, suggesting their roles in plant growth and development. Some of the genes showed differential expression against C. gloeosporioides inoculation and hormone (SA and JA) treatments, signifying their critical roles in plant response to pathogen and hormone treatments. Moreover, ectopic expression of FvDIR13 (Acc. NO. MZ318691) in Arabidopsis thaliana exhibited enhanced resistance to C. higginsianum, increase in lignin contents, and change in expression of genes having presumed roles in JA and SA signaling pathways. We surmise that FvDIR13 can promote lignin synthesis, and has roles in disease resistance via regulating JA and SA responsive genes. Our findings give a new foundation for understanding the functions of FvDIR genes and provide preliminary information about the roles of FvDIR13 in disease resistance.