Isolation and functional characterization of SUCROSE SYNTHASE 1 and SUCROSE TRANSPORTER 2 promoters from ramie (Boehmeria nivea L. Gaudich)

Molecular characterization of SUT Gene Family in Solanaceae with emphasis on expression analysis of pepper genes during development and stresses

Sucrose, an essential carbohydrate, is transported from source to sink organs in the phloem and is involved in a variety of physiological and metabolic processes in plants. Sucrose transporter proteins (SUTs) may play significant parts in the phloem loading and unloading of sucrose. In our study, the SUT gene family was identified in four Solanaceae species (Capsicum annuum, Solanum lycopersicum, S. melongena, and S. tuberosum) and other 14 plant species ranged from lower and high plants. The comprehensive analysis was performed by integration of chromosomal distribution, gene structure, conserved motifs, evolutionary relationship and expression profiles during pepper growth under stresses. Chromosome mapping revealed that SUT genes in Solanaceae were distributed on chromosomes 4, 10 and 11. Gene structure analysis showed that the subgroup 1 members have the same number of introns and exons. All the SUTs had 12 transmembrane structural domains exception from CaSUT2 and SmSUT2, indicating that a structure variation might occurred among the Solanaceae SUT proteins. We also found a total of 20 conserved motifs, with over half of them shared by all SUT proteins, and the SUT proteins from the same subgroup shared common motifs. Phylogenetic analysis divided a total of 72 SUT genes in the plant species tested into three groups, and subgroup 1 might have diverged from a single common ancestor prior to the mono-dicot split. Finally, expression levels of CaSUTs were induced significantly under heat, cold, and salt treatments, indicating diverse functions of the CaSUTs to adapt to adverse environments.

Promoter P PSP1-5-BnPSP-1 From Ramie (Boehmeria nivea L. Gaud.) Can Drive Phloem-Specific GUS Expression in Arabidopsis thaliana

Isolation of phloem-specific promoters is one of the basic conditions for improving the fiber development and resistance of ramie phloem using genetic engineering. In this study, we isolated a ramie endogenous promoter (named P_PSP1-BnPSP-1) and analyzed the function of its truncated fragments in Arabidopsis. The results show that P_PSP1-BnPSP-1 can drive the GUS reporter gene to be specifically expressed in the veins of Arabidopsis. After hormone and simulated drought treatment of the independent Arabidopsis lines carrying P_PSP1-BnPSP-1 and its truncated fragments, only P_PSP1–5-BnPSP-1 (−600 to −1 bp region of P_PSP1-BnPSP-1) is stably expressed and exhibits phloem specificity. Our findings suggest that P_PSP1–5-BnPSP-1 can be used as a phloem specific promoter for further research.

Integrative Transcriptome and Proteome Analysis Identifies Major Molecular Regulation Pathways Involved in Ramie (Boehmeria nivea (L.) Gaudich) under Nitrogen and Water Co-Limitation

Water and N are the most important factors affecting ramie (Boehmeria nivea (L.) Gaudich) growth. In this study, de novo transcriptome assembly and Tandem Mass Tags (TMT) based quantitative proteome analysis of ramie under nitrogen and water co-limitation conditions were performed, and exposed to treatments, including drought and N-deficit (WdNd), proper water but N-deficit (WNd), proper N but drought (WdN), and proper N and water (CK), respectively. A total of 64,848 unigenes (41.92% of total unigenes) were annotated in at least one database, including NCBI non-redundant protein sequences (Nr), Swiss-Prot, Protein family (Pfam), Gene Ontology (GO) and KEGG Orthology (KO), and 4268 protein groups were identified. Most significant changes in transcript levels happened under water-limited conditions, but most significant changes in protein level happened under water-limited conditions only with proper N. Poor correlation between differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) was observed in ramie responding to the treatments. DEG/DEP regulation patterns related to major metabolic processes responding to water and N deficiency were analyzed, including photosynthesis, ethylene responding, glycolysis, and nitrogen metabolism. Moreover, 41 DEGs and 61 DEPs involved in regulating adaptation of ramie under water and N stresses were provided in the study, including DEGs/DEPs related to UDP—glucuronosyhransferase (UGT), ATP synthase, and carbonate dehydratase. The strong dependency of N-response of ramie on water conditions at the gene and protein levels was highlighted. Advices for simultaneously improving water and N efficiency in ramie were also provided, especially in breeding N efficient varieties with drought resistance. This study provided extensive new information on the transcriptome, proteome, their correlation, and diversification in ramie responding to water and N co-limitation.