Genome Identification of B-BOX Gene Family Members in Seven Rosaceae Species and Their Expression Analysis in Response to Flower Induction in Malus domestica

BBX proteins play important roles in regulating plant growth and development including photomorphogenesis, photoperiodic regulation of flowering, and responses to biotic and abiotic stresses. At present, the genomes of seven fruit species have been fully sequenced. However, little is known about the gene family and their evolutionary history in these species. Therefore, in this study total, 212 genes were investigated from seven species (67 from × , 40 from , 22 from , 20 from , 21 from , 22 from , and 20 from ). The chemical properties, gene structures, and evolutionary relationships of the genes were also studied. All the genes were grouped into six subfamilies on the basis of their phylogenetic relationships and structural features. Analysis of gene structure, segmental and tandem duplication, gene phylogeny, and tissue-specific expression with the ArrayExpress database showed their diversification in function, quantity, and structure. The expression profiles of 19 genes in different tissues were evaluated through qRT-PCR. These genes showed distinct transcription level among the tested tissues (bud, flower, fruit, stem, and leaf). Moreover, expression patterns of 19 genes were examined during flowering induction time under flowering-related hormones and treatments (GA3, 6-BA, and sucrose). The expressions of the candidates genes were affected and showed diverse expression profile. Furthermore, changes in response to these flowering-related hormones and treatment specifying their potential involvement in flowering induction. Based on these findings, genes could be used as potential genetic markers for the growth and development of plants particularly in the area of functional analysis, and their involvement in flower induction in fruit plants.