Genome-Wide Discovery and Expression Profiling of the SWEET Sugar Transporter Gene Family in Woodland Strawberry (Fragaria vesca) under Developmental and Stress Conditions: Structural and Evolutionary Analysis

The SWEET(sugar will eventually be exported transporter)family proteins are a recently identified class of sugar transporters that are essential for various physiological processes.Although the functions of the SWEET proteins have been identified in a number of species,to date,there have been no reports of the functions of the SWEET genes in woodland strawberries(Fragaria vesca).In this study,we identified 15 genes that were highly homolo-gous to the A.thaliana AtSWEET genes and designated them as FvSWEET1–FvSWEET15.We then conducted a structural and evolutionary analysis of these 15 FvSWEET genes.The phylogenetic analysis enabled us to categor-ize the predicted 15 SWEET proteins into four distinct groups.We observed slight variations in the exon‒intron structures of these genes,while the motifs and domain structures remained highly conserved.Additionally,the developmental and biological stress expression profiles of the 15 FvSWEET genes were extracted and analyzed.Finally,WGCNA coexpression network analysis was run to search for possible interacting genes of FvSWEET genes.The results showed that the FvSWEET10 genes interacted with 20 other genes,playing roles in response to bacterial and fungal infections.The outcomes of this study provide insights into the further study of FvSWEET genes and may also aid in the functional characterization of the FvSWEET genes in woodland strawberries.

枸杞SWEET基因家族鉴定及其与可溶性糖含量关系

【目的】糖外排转运蛋白(sugars will eventually be exported transporters,SWEETs)在植物生长发育过程中发挥重要作用,解析SWEETs基因在枸杞果实发育过程中对糖积累作用,为进一步揭示SWEETs基因在枸杞果实发育过程中的作用提供参考。【方法】用生物信息学方法对枸杞SWEET基因(LbaSWEETs)进行全基因组鉴定,并用已发表的转录数据分析LbaSWEETs在果实发育时期的基因表达情况。【结果】枸杞SWEET基因家族共有37个成员,随机分布于10条染色体上,分别编码152~621个氨基酸,蛋白质分子质量为16.87~69.97 kD,等电点为4.96~9.86。亚细胞定位预测位于叶绿体或质膜,大多数含有7个跨膜螺旋。系统进化分析发现,37个LbaSWEETs蛋白可分为4个亚群,每个亚群的基因结构和保守基序组成相似。启动子元件分析表明:Lba-SWEETs基因启动子富含大量激素响应、逆境胁迫和生长发育响应元件。转录组数据和qRT-PCR分析表明:LbaSWEET9和LbaSWEET29基因表达量随果实成熟呈现显著增加。相关性分析结果表明,LbaSWEET9和LbaSWEET29基因表达量与果糖含量呈显著正相关。【结论】LbaSWEET9和LbaSWEET29基因是果糖积累的关键基因。

Impaired SWEET-mediated sugar transportation impacts starch metabolism in developing rice seeds

Sugar transportation and sugar-to-starch metabolism are considered important processes in seed development and embryo viability.A few plant SWEET proteins acting as sugar transporters have been reported to function in inflorescence and/or seed development.Here,we identified seven members of the 21 Os SWEET genes in rice that play essential roles in sugar transportation and sugar-to-starch conversion in seed development.Nineteen Os SWEET genes exhibiting different expression patterns during inflorescence and seed development were knocked out individually by CRISPR/Cas9.One third of the mutants showed decreased fertile pollen viability and shriveled mature caryopses,resulting in weakened seed traits.Grain fill-related genes but not representative grain shape-regulating genes showed attenuated expression in the mutants.Seed of each of these mutants accumulated more sucrose,glucose or fructose but less starch.Among all Os SWEET genes,Os SWEET4 and Os SWEET11 had major effects on caryopsis development.The sugar-to-starch metabolic pathway was significantly altered in ossweet11 mutants based on differential expression analysis in RNA sequencing assays,confirming that Os SWEET11 functions as a sugar transporter with a key role in seed development.These results help to decipher the multiple functions of Os SWEET genes and to show how they might be used in genetic improvement of rice.

Plasma membrane-localized SlSWEET7a and SlSWEET14 regulate sugar transport and storage in tomato fruits

Sugars,especially glucose and fructose,contribute to the taste and quality of tomato fruits.These compounds are translocated from the leaves to the fruits and then unloaded into the fruits by various sugar transporters at the plasma membrane.SWEETs,are sugar transporters that regulate sugar efflux independently of energy or pH.To date,the role of SWEETs in tomato has received very little attention.In this study,we performed functional analysis of SlSWEET7a and SlSWEET14 to gain insight into the regulation of sugar transport and storage in tomato fruits.SlSWEET7a and SlSWEET14 were mainly expressed in peduncles,vascular bundles,and seeds.Both SlSWEET7a and SlSWEET14 are plasma membrane-localized proteins that transport fructose,glucose,and sucrose.Apart from the resulting increase in mature fruit sugar content,silencing SlSWEET7a or SlSWEET14 resulted in taller plants and larger fruits(in SlSWEET7a-silenced lines).We also found that invertase activity and gene expression of some SlSWEET members increased,which was consistent with the increased availability of sucrose and hexose in the fruits.Overall,our results demonstrate that suppressing SlSWEET7a and SlSWEET14 could be a potential strategy for enhancing the sugar content of tomato fruits.

The Comparison of Sugar Components in the Developing Grains of Sweet Corn and Normal Corn

The sugar components and their dynamic variation in the developing grains of sweet corn(Zea mays L. seccharata Sturt)and normal corn (Zea mays L. indentata Sturt) were compared. There are WSP (water-soluble polysaccharides), sucrose, fructose, glucose, mannitol and sorbitol in both sweet corn and normal corn, but no maltose. Two components with different degrees of polymerization (D. P. N) were detected in the sweet corn; only one of them was detected in the normal corn 20 days after pollination. With the development of grains, the total soluble sugar content(TSS)in sweet corn increased, but in normal corn it decreased. The dynamic variation of WSP, sucrose, glucose, fructose, mannitol and sorbitol in sweet and normal corn grains are different. The contents of sugar components in the sweet corn grains are higher than that in the normal corn. Sweet corn accumulates less starch than normal corn.

植物SWEET基因及其糖转运功能研究进展

SWEET(sugars will eventually be exported transporter)是一类介导蔗糖或己糖通过顺浓度梯度被动扩散跨细胞膜转运的新型糖转运蛋白。植物SWEET蛋白包括7个跨膜结构域,其中包含2个MtN3/Saliva结构域,可分为4个进化分支。SWEET转运蛋白在多种生理和生化过程中发挥着关键作用,包括韧皮部装载、激素运输、营养和生殖生长等。结合当前SWEET转运蛋白的研究进展,重点总结了SWEET的发现、蛋白结构及其在糖转运中的生物学功能,指出目前植物SWEET基因研究面临的问题,并对未来SWEET蛋白的研究重点进行了展望:1)探究SWEET蛋白的底物识别机制;2)挖掘提高作物产量和品质的关键SWEET基因;3)利用SWEET基因编辑和磷酸化等策略改良作物产量和品质。

Research Progress on Genetic Breeding of Sweet Sorghum Related to Sugar Traits

Sweet sorghum is a crop with good application prospects, and the research on sweet sorghum breeding people should be strengthened. Based on this, the genetic content of QTLs(quantitative trait loci) for sugar traits in sweet sorghum was introduced, and the analysis content of the genetic breeding of sweet sorghum related to sugar traits was expounded, providing support for the cultivation of sweet sorghum with higher quality and the promotion of agricultural development in China.

Nitrogen Fertilizer and Panicle Removal in Sweet Sorghum Production: Effect on Biomass, Juice Yield and Soluble Sugar Content

Alternative and renewable bio-based energy sources are gaining prominence worldwide. Sweet sorghum is currently being evaluated throughout the world because its stem juices are rich in sugars that can be directly fermented to ethanol. In this two-year study, sweet sorghum varieties;Dale, Theis, Topper 76-6, and M81E (Obtained from Mississippi State University Experiment Station, MS) and CHR-SW8 (Obtained from Chromatin Inc., IL) were used. Nitrogen (N) fertilizer rates of 0, 40, 80 or 120 kg·N·ha-1 were applied to experimental units. The experiment was a randomized complete block design with treatments in a split-split plot arrangement with three replications. Nitrogen rate was the main plot, cultivar as sub-plot, and panicle removal as sub-plot. Results showed that N application increased fresh stem yield, juice volume, but had minimal effect on juice soluble sugar concentration. Compared to controls, application of ≥40 kg·N·ha-1 increased fresh yield and juice by >60% and 10%, respectively. There were also variety differences in harvested fresh biomass, juice volume and oBrix, and soluble sugar content. Dale and Theis consistently showed lower sucrose compared to other varieties over the two years. Panicle removal during early reproductive phase increased oBrix, sucrose and total sugar content in all varieties. Across the two years of study, panicle removal increased oBrix by more than 10%, sucrose and total sugar increased by more than 20%. Selection of varieties that produce high juice volume with high sugar content and strategies to inhibit seed formation may result in improved juice quality.

植物糖转运蛋白SWEETs研究进展

植物碳水化合物在“源流库”不同组织器官中的合成、代谢及转运对有机体维持正常生命活动至关重要。其中,以蔗糖、葡萄糖和果糖为代表的糖类短距离或长距离运输在源到库的“流”中占有关键作用,在此过程中,碳水化合物的转运与分配需要多种细胞糖转运体的协同参与。糖外排转运蛋白(SWEETs)能够调节植物营养的分配、利用,决定组织器官的生长与发育,维持或调节细胞糖响应浓度,调节寄主-病原体相互作用等生物与非生物胁迫。本综述介绍了SWEETs基因家族基本结构特征、生理功能和胁迫应答等方面的研究进展,对植物细胞生理功能的理解和生物育种等研究具有重要意义。

植物SWEET基因家族结构、功能及调控研究进展

SWEET(sugars will eventually be exported transporter)基因家族是一类新型的糖转运蛋白,可顺浓度梯度对糖分进行双向跨膜运输。SWEET在植物光合同化物韧皮部装载、蜜腺花蜜分泌、种子灌浆、花粉发育、病原菌互作、逆境调控等过程中起着关键作用,近年来受到广泛关注。尽管SWEET广泛存在于植物中,但目前对其功能研究主要集中在水稻和拟南芥上。介绍了SWEET基因家族的发现、蛋白结构特征、生理功能及逆境调控的最新研究进展,有助于将来对SWEET基因家族进行更深入和全面的研究。

SWEET转运蛋白在作物中的功能研究及前景展望

WEET是近年来新发现的一类糖转运蛋白,在植物中参与光合产物的运输和分配,从而调控植物响应逆境胁迫、抵抗病原菌侵染以及种子形成和发育等生理过程。本研究综述了作物中SWEET基因家族功能的最新进展,初步归纳了水稻、玉米、大豆和高粱等作物的SWEET蛋白在糖分转运和分配过程中的功能,有助于解析SWEET蛋白家族提高作物产量的机理。

Optimization of the Fermentation Conditions of Sweet Oats by Response Surface Methodology

Objective] The purpose of this study was to evaluate the effects of five variables （steaming time, moisture content before inoculation, inoculation amount, fer-mentation temperature, fermentation time） on the sweetness of sweet oats, obtained the best fermentation conditions. [Method] Plackett-Burman （PB） was to evaluate the effects of five variables, and selected significant factors. The steepest ascent was used to approach the optimal response surface experimental area. The optimal fer-mentation condition was obtained by central composite design and response surface analysis. [Results] It was indicated that moisture content, inoculation amount and fer-mentation temperature had significant influences on the content of the reducing sugars. The optimal conditions of moisture content, inoculation amount and temper-ature were 45.26%, 0.014%（g/g） and 28 ℃, respectively. The predicted value of the reducing sugar content was 13.16 mg/g. [Conclusion] Under the optimal conditions, the content of the reducing sugars in the sweet oats could be up to 12.91 mg/g, which was on the whole consistent with the predictive maximum value.

VIGS技术鉴定木薯糖转运蛋白Mesweet18的功能研究

糖转运蛋白(sugar will eventually be exported transporter,SWEET)在植物运输糖类、生殖和发育、逆境性、与病原体互作等方面发挥着重要作用。选择木薯糖转运蛋白Mesweet18基因沉默的靶基因区域,通过病毒诱导的基因沉默(virus-induced gene silencing,VIGS)技术注射木薯SC9的盆栽苗叶片。qRT-PCR结果表明,Mesweet18在沉默植株中的表达量显著下调,分别是对照的46.80%、30.23%、21.12%。叶片叶绿素和可溶性糖含量检测结果表明,与对照相比,叶绿素a、b和总含量均出现不同程度的下降,蔗糖和果糖含量显著增加,而葡萄糖含量出现轻微下降。研究Mesweet18在木薯中的分子功能,为深入研究糖转运蛋白SWEET在木薯中的分子机制奠定了基础。

甘薯糖转运蛋白IbSWEET15的功能研究

SWEET蛋白在植物生长发育、胁迫响应和糖代谢过程中具有重要的调控作用,而甘薯SWEET蛋白的研究鲜有报道。开展甘薯SWEET蛋白功能研究,揭示其在糖转运及淀粉与糖代谢中的功能,具有重要的理论与实践意义。根据不同淀粉性状甘薯块根中差异表达的SWEET编码基因转录本,设计引物进行RACE克隆,获得IbSWEET15全长cDNA序列。利用在线软件对IbSWEET15进行生物信息学分析,并构建系统发育树明确其分类。通过在本氏烟草中瞬时表达IbSWEET15-GFP融合蛋白,明确IbSWEET15的亚细胞定位;以酵母突变体互补试验,验证IbSWEET15蛋白在酵母中的糖转运功能。通过实时荧光定量PCR(qRT-PCR)分析IbSWEET15在甘薯各器官中的表达特征;构建IbSWEET15表达载体并通过蘸花法转化拟南芥野生型Col-0,获得IbSWEET15异源表达拟南芥株系,比较转基因株系与野生型拟南芥植株的淀粉和糖含量差异,以明确IbSWEET15在淀粉和糖代谢过程中的功能。IbSWEET15基因开放阅读框为879 bp,编码292个氨基酸组成的SWEET蛋白,具有2个MtN3_slv保守结构域及7个跨膜结构域,属于SWEET蛋白家族第III分支成员。IbSWEET15定位于质膜,在酵母中无蔗糖和己糖转运功能,其编码基因在甘薯侧枝中表达量最高,主茎、叶次之,块根中最低。IbSWEET15的拟南芥过表达株系的叶片可溶性糖含量显著下降,而种子可溶性糖和淀粉含量均高于野生型。推测IbSWEET15可能在光合产物源-库运输过程中的韧皮部装载以及植株淀粉和糖积累方面具有重要作用。本研究为揭示IbSWEET15在甘薯淀粉和糖代谢及重要品质性状形成中的功能提供了重要信息。

植物SWEET基因家族的相关研究进展

为了深入研究近年来新发现的一类糖转运蛋白SWEET基因家族在植物中的作用,本研究介绍了植物SWEET基因家族的发现,归纳总结了SWEET基因的蛋白质结构、进化分析结果和在植物中的生理功能。指出SWEET转运蛋白具有多种不同的生理功能,在植物生长发育及代谢活动中起了重要的作用。为后续在植物中研究SWEET基因家族提供一定的理论基础。

Genome-wide identification, characterization, and expression analysis of the SWEET gene family in cucumber

SWEETs （sugars will eventually be exported transporters） are a novel class of recently identified sugar transporters that play important roles in diverse physiological processes. However, only a few species of the plant SWEETgene family have been functionally identified. Up till now, there has been no systematic analysis of the SWEETgene family in Cucurbitaceae crops. Here, a genome-wide characterization of this family was conducted in cucumber（Cucumis sativus L.）. A total of 17 CsSWEETgenes were identified, which are not evenly distributed over the seven cucumber chromosomes. Cucumber SWEET protein sequences possess seven conserved domains and two putative serine phosphorylation sites. The phylo- genetic tree of the SWEET genes in cucumber, Arabidopsis thaliana, and Oryza sativa was constructed, and all the SWEET genes were divided into four clades. In addition, a number of putative cis-elements were identified in the promoter regions of these CsSWEET genes： nine types involved in phytohormone responses and eight types involved in stress responses. Moreover, the transcript levels of CsSWEETgenes were analyzed in various tissues using quantitative real-time polymerase chain reaction. A majority （70.58%） of the CsSWEET genes were confined to reproductive tissue development. Finally, 18 putative watermelon ClaSWEETgenes and 18 melon CmSWEETgenes were identified that showed a high degree of similarity with CsSWEETgenes. The results from this study provided a basic understanding of the CsSWEETgenes and may also facilitate future research to elucidate the function of SWEET genes in cucumber and other Cucurbitaceae crops.

植物SWEET基因家族的研究进展

植物糖转运蛋白SWEET基因家族是近年来发现的一类重要的糖转运蛋白,通过调节糖分在植物体内的转运及分配等,进而在植物的生长发育、生理代谢、抗逆境胁迫等方面起着重要作用。不同物种中SWEET基因所表现的生物学功能不同,对植物生物生命活动起着重要影响。本研究报告了植物SWEET基因家族的蛋白结构、转运机制以及生物学功能的研究现状,旨在为进一步研究SWEET基因家族的其他结构与功能提供理论基础。

Transcriptional dynamics of the developing sweet cherry(Prunus avium L.)fruit:sequencing,annotation and expression profiling of exocarp-associated genes

The exocarp,or skin,of fleshy fruit is a specialized tissue that protects the fruit,attracts seed dispersing fruit eaters,and has large economical relevance for fruit quality.Development of the exocarp involves regulated activities of many genes.This research analyzed global gene expression in the exocarp of developing sweet cherry(Prunus avium L.,‘Regina’),a fruit crop species with little public genomic resources.A catalog of transcript models(contigs)representing expressed genes was constructed from de novo assembled short complementary DNA(cDNA)sequences generated from developing fruit between flowering and maturity at 14 time points.Expression levels in each sample were estimated for 34695 contigs from numbers of reads mapping to each contig.Contigs were annotated functionally based on BLAST,gene ontology and InterProScan analyses.Coregulated genes were detected using partitional clustering of expression patterns.The results are discussed with emphasis on genes putatively involved in cuticle deposition,cell wall metabolism and sugar transport.The high temporal resolution of the expression patterns presented here reveals finely tuned developmental specialization of individual members of gene families.Moreover,the de novo assembled sweet cherry fruit transcriptome with 7760 full-length protein coding sequences and over 20000 other,annotated cDNA sequences together with their developmental expression patterns is expected to accelerate molecular research on this important tree fruit crop.

甜瓜果实发育相关SWEET糖转运蛋白基因的鉴定与功能初步分析

甜瓜是我国,也是世界上最重要的夏令水果之一。甜瓜果实内所含碳水化合物的种类和数量很大程度上决定其品质和产量。SWEET(sugars will eventually be exported transporters)糖转运蛋白具有运输葡萄糖和其他寡糖的功能,最近研究表明,SWEET糖转运蛋白在果实发育中可能起调控作用。本研究从甜瓜基因组中鉴定获得18个SWEETs糖转运蛋白基因,进一步通过RT-PCR并结合实时荧光定量PCR(quantitative real-time PCR,qPCR)方法,筛选到3个SWEETs基因在整个果实发育期内或某个发育时期表达量较高。亚细胞定位显示,两个SWEETs基因(CmSWEET3,CmSWEET7a)定位在细胞膜上。进一步通过酵母表达发现,甜瓜CmSWEET7a在体外具有转运葡萄糖和果糖的功能。本研究为揭示SWEET糖转运蛋白在甜瓜果实发育过程的调控作用奠定了基础。

A genome-wide analysis of SWEET gene family in cotton and their expressions under different stresses

Background： The SWEET （Sugars will eventually be exported transporters） gene family plays multiple roles in plant physiological activities and development process. It participates in reproductive development and in the process of sugar transport and absorption, plant senescence and stress responses and plant-pathogen interaction. However, thecomprehensive analysis of SWEET genes has not been reported in cotton. Results： In this study, we identified 22, 31, 55 and 60 SWEETgenes from the sequenced genomes of Gossypium orboreum, G. rairnondii, G. hirsutum and G. borbadense, respectively. Phylogenetic tree analysis showed that the SWEET genes could be divided into four groups, which were further classified into 14 sub-clades. Further analysis of chromosomal location, synteny analysis and gene duplication suggested that the orthologs showed a good collinearity and segmental duplication events played a crucial role in the expansion of the family in cotton. Specific MtN3_slv domains were highly conserved between Arabidopsis and cotton by exon-intron organization and motif analysis. In addition, the expression pattern in different tissues indicated that the duplicated genes in cotton might have acquired new functions as a result of sub-functionalization or neo-functionalization. The expression pattern of SWEET genes showed that the different genes were induced by diverse stresses. The identification and functional analysis of SWEET genes in cotton may provide more candidate genes for genetic modification. Conclusion： SWEET genes were classified into four clades in cotton. The expression patterns suggested that the duplicated genes might have experienced a functional divergence. This work provides insights into the evolution of SWEETgenes and more candidates for specific genetic modification, which will be useful in future research.