Genome-wide analysis of the SWEET gene family in Hemerocallis citrina and functional characterization of HcSWEET4a in response to salt stress

Abstract Sugars will be eventually effluxed transporter (SWEET), one of the sugar transporters in plants, plays significant roles in numerous biological processes and responding to abiotic stressors. However, the characteristics and functions of the SWEET genes in Hemerocallis citrina remain unclear and poorly elucidated. In this study, the whole genome of Hemerocallis citrina was utilized to conduct bioinformatics analysis and a total of 19 HcSWEET genes were successfully identified. Analysis of the physicochemical properties indicated dominant differences among these HcSWEETs. A phylogenetic analysis revealed that HcSWEET proteins can be divided into 4 clades ranging from Clade I to IV, where proteins within the same clade exhibited shared conserved motifs and gene structures. Five to six exons were contained in the majority of HcSWEET genes, which were unevenly distributed across 11 chromosomes. The gene duplication analysis showed the presence of 4 gene pairs. Comparative syntenic maps revealed that the HcSWEET gene family might present more closed homology in monocotyledons than dicotyledons. Cis-acting element analysis of HcSWEET genes indicated key responsiveness to various hormones, light, and stresses. Additionally, transcriptome sequencing analysis suggested that most HcSWEET genes had a relatively higher expression in roots, and HcSWEET4a was significantly up-regulated under salt stress. Overexpression further verified the possibility that HcSWEET4a is involved in response to salt stress, which provides novel insights and facilitates in-depth studies of the functional analysis of HcSWEETs in resistance to abiotic stress.