The Ubiquitin-Conjugating Enzyme Gene Family in Longan (Dimocarpus longan Lour.): Genome-Wide Identification and Gene Expression during Flower Induction and Abiotic Stress Responses.

Ubiquitin-conjugating enzymes (E2s or UBC enzymes) play vital roles in plant development and combat various biotic and abiotic stresses. Longan ( Lour.) is an important fruit tree in the subtropical region of Southeast Asia and Australia; however the characteristics of the gene family in longan remain unknown. In this study, 40 UBC genes (), which were classified into 15 groups, were identified in the longan genome. An RNA-seq based analysis showed that showed distinct expression in nine longan tissues. Genome-wide RNA-seq and qRT-PCR based gene expression analysis revealed that 11 were up- or down-regualted in the cultivar "Sijimi" (SJ), suggesting that these genes may be important for flower induction. Finally, qRT-PCR analysis showed that the mRNA levels of 13 under SA (salicylic acid) treatment, seven under methyl jasmonate (MeJA) treatment, 27 under heat treatment, and 16 under cold treatment were up- or down-regulated, respectively. These results indicated that the may play important roles in responses to abiotic stresses. Taken together, our results provide a comprehensive insight into the organization, phylogeny, and expression patterns of the longan UBC genes, and therefore contribute to the greater understanding of their biological roles in longan.