LoSWEET14, a Sugar Transporter in Lily, Is Regulated by Transcription Factor LoABF2 to Participate in the ABA Signaling Pathway and Enhance Tolerance to Multiple Abiotic Stresses in Tobacco

Abstract

Sugar transport and distribution plays an important role in lily bulb development and resistance to abiotic stresses. In this study, a member of the Sugar Will Eventually be Exported Transporters (SWEET) gene family, LoSWEET14, from Oriental hybrid lily ‘Sorbonne’ was identified. LoSWEET14 encodes a protein of 278 amino acids and is capable of transporting sucrose and some types of hexoses. The transcript level of the LoSWEET14 gene was significantly increased under various stress conditions including drought, cold, salt stresses, and abscisic acid (ABA) treatment. Overexpression of LoSWEET14 in tobacco (Nicotiana tabacum) showed that the transgenic lines had larger leaves, accumulated more soluble sugars, and were more resistant to drought, cold, and salt stresses, while becoming more sensitive to ABA compared with wild-type lines. Promoter analysis revealed that multiple stress-related cis-acting elements were found in the promoter of LoSWEET14. According to the distribution of cis-acting elements, different lengths of 5′-deletion fragments were constructed and the LoSWEET14-pro3(-540 bp) was found to be able to drive GUS gene expression in response to abiotic stresses and ABA treatment. Furthermore, a yeast one hybrid (Y1H) assay proved that the AREB/ABF (ABRE-binding protein/ABRE-binding factor) from lilies (LoABF2) could bind to the promoter of LoSWEET14. These findings indicated that LoSWEET14 is induced by LoABF2 to participate in the ABA signaling pathway to promote soluble sugar accumulation in response to multiple abiotic stresses.

Identification and Characterization of the AREB/ABF Gene Family in Three Orchid Species and Functional Analysis of DcaABI5 in Arabidopsis

“…As observed in other plants [ 42 , 43 , 44 , 45 , 46 , 47 , 48 ], phylogenetically close AREB/ABF s members always have relatively consistent compositions of motifs and exons/introns, suggesting that these AREB/ABF subgroup proteins might share a similar functionality ( Figure 3 ). Of the 10 conserved motifs identified in all the AREB/ABF proteins, motif 1 and motif 2-5 were highly consistent, which consist of the conserved bZIP domain and the phosphorylation domains C1–C3, respectively ( Figure 3 ).…”

“…Previous studies have reported AREB/ABF genes from various plants improve stress adaptability and resistance, such as in Arabidopsis [ 24 ], rice [ 34 ], wheat [ 37 , 38 , 39 ], potato [ 40 , 41 ], cotton [ 42 ], apple [ 43 ], strawberry [ 44 ], rose [ 45 ], lily [ 46 ], kiwifruit [ 47 ], and jute [ 48 ]. To date, the AREB/ABF subfamily in orchid plants remains largely unknown.…”

Identification and Characterization of <em>AREB/ABF</em> Gene Family in Three Orchid Species and Functional Analysis of <em>DcaABI5</em> in <em>Arabidopsis</em>

“…As observed in other plants [42][43][44][45][46][47][48], phylogenetically close AREB/ABFs members always have relatively consistent compositions of motifs and exons/introns, suggesting that these AREB/ABF subgroup proteins might share a similar functionality (Figure 3). Of the 10 conserved motifs identified in all the AREB/ABF proteins, motif 1 and motif 2-5 were highly consistent, which consist of the conserved bZIP domain and the phosphorylation domains C1-C3, respectively (Figure 3).…”

Identification and Expression Analysis of Putative Sugar Transporter Gene Family during Bulb Formation in Lilies

“…Sugar transporter genes constitute a versatile gene family, and they play critical roles in many biological processes during plant growth and responses to environmental stimuli [ 7 , 12 ]. LoSWEET14 is a sugar transporter that has been identified in recent years as potentially involved in the abscisic acid (ABA) signaling pathway to regulate sugar accumulation under abiotic stresses in lilies [ 60 ]. In our study, the counterpart to LoSWEET14 is LohSWEET4 , which has >90% sequence similarity and was significantly expressed during bulblet initiation 8 days after aeroponics, which suggests LohSWEET4 might be crucial for adventitious bud initiation and needs further verification.…”