Abstract
The quality of Lily cut flower was determined by the quality of bulbs. During the process of vernalization and flower bud differentiation, sugar massively accumulated in the bulb, which influenced the bulb development. However, the details of sugar genes’ regulation mechanism for these processes were not fully understood. Here, morphological physiology, transcriptomes and gene engineering technology were used to explore this physiological change. Seventy-two genes of 25 kinds of sugar metabolism-related genes were annotated after re-analyzing transcriptome data of Oriental hybrid lily ‘Sorbonne’ bulbs, which were generated on Hiseq Illumina 2000. The results showed that these genes were closely related to lily bulb vernalization and development. Combining gene expression pattern with gene co-expression network, five genes (Contig5669, Contig13319, Contig7715, Contig1420 and Contig87292) were considered to be the most potential signals, and the sucrose transporter gene (SUT) was the focus of this study. Carbohydrate transport pathway and genes’ regulation mechanism were inferred through a physiological and molecular test. SUT seemed to be the sugar sensor that could sense and regulate sugar concentration, which might have effects on other genes, such as FT, LFY and so on. LoSUT2 and LoSUT4 genes were cloned from Oriental hybrid lily ‘Sorbonne’ by RACE, which was the first time for these genes in Oriental hybrid lily ‘Sorbonne’. The physiological properties of these proteins were analyzed such as hydrophobicity and phosphorylation. In addition, secondary and tertiary structures of proteins were predicted, which indicated the two proteins were membrane proteins. Their cellular locations were verified through positioning the experiment of the fluorescent vector. They were highly expressed in cells around phloem, which illustrated the key role of these genes in sugar transport. Furthermore, transient expression assays showed that overexpressed LoSUT2 and LoSUT4 in Arabidopsis thaliana bloomed significantly earlier than the wild type and the expression of FT, SOC1 and LFY were also affected by LoSUT2 and LoSUT4, which indicated that LoSUT2 and LoSUT4 may regulate plants flowering time.
Highlights
Sucrose is the major solute for most plant species
Through the study of Oriental hybrid lily ‘Sorbonne’, we further explored the importance of carbohydrates in the development of oriental lily bulbs, and the internal molecular regulation mechanism of the carbohydrate metabolism gene (SUT)
Taking the Invertase gene (INV) as an example, the gene sequences and protein sequences were collected in the nucleotide database of NCBI
Summary
Sucrose is the major solute for most plant species It can provide nutrients for plant growth and development as the carbon source, and participate in the signal transduction process in plants as a signal substance [1,2]. Sucrose is the predominant carbohydrate transported from sink to source tissues for long-distance translocation by sugar transporters, among which sucrose transporters (SUTs) play an important role in phloem loading and unloading [5,6]. Some SUTs are characterized by large cytoplasmic loop regions and are reputed to play a role in sugar sensing. Many reports have shown the transcriptional regulation of SUT genes in various developmental processes, by environmental factors such as light and salt stress, and by endogenous signals such as sugars and hormones [11,12,13]. It is likely that SUTs are subject to complex regulation at different levels
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