Dragon fruit comprises a wide variety of species that are rich in nutritional value and have great economic potential; however, numerous studies have focused on their nutritional and commercial quality. In contrast, few studies have addressed their flavor quality, particularly with respect to the regulatory networks responsible for their flavor-related substance contents. To this end, we sequenced the transcriptomes and metabolomes of red-skin/white-fleshed and red-skin/red-fleshed dragon fruit at different timepoints during fruit development. RNA-seq and metabolome data were used to divide the seven developmental stages of the dragon fruit into four categories (young fruit, expansion, maturity, and senescence). In all, 16,827 differentially expressed genes (DEGs), including 958 transcription factors, were identified and grouped into 10 clusters, and the pathways in each cluster were annotated. Additionally, 318 differentially accumulated metabolites (DAMs) were identified, including 88 common metabolites. The main flavor-related substances and the key genes regulating them were determined via joint analysis via RNA-seq and metabolomics. Furthermore, 10 volatile active components related to green flavors and aromas were screened according to the relative odor activity value (ROAV), and 15 candidate genes related to key flavor compounds were screened via WGCNA, 3 of which encoded transcription factors. In conclusion, our results provide a theoretical basis for an in-depth understanding of the volatile flavor compounds in dragon fruit and provide new genetic resources for the subsequent study of fruit flavor compounds.

Aroma is one of the major inherent quality characteristics in fruits. Understanding the composition of aroma volatiles and their biosynthesis mechanism is crucial to improving fruit quality. However, the biosynthesis mechanism of aroma volatiles has not been characterized yet in white-fleshed pitaya (Hylocereus undatus). This study was performed to investigate aroma volatiles and related gene expression patterns in the pulp of "mild grassy" and "strong grassy" aroma cultivars. Analysis of volatile composition and concentration showed that aldehydes, alcohols, esters, and alkenes were predominant in both cultivars. However, comparative analysis revealed a significant difference in the concentration of several metabolites, particularly hexanal and 1-hexanol. The results of the comparative transcriptome identified a large number of aroma-related differentially expressed genes. The majority of these genes were enriched in fatty acid and isoleucine degradation pathways. According to integrative analyses, changes in the expression of lipoxygenase pathway genes, specifically FAD, LOXs, HPLs, and ADHs, probably lead to the difference in strength of "grassy" aroma between both cultivars. The qRT-PCR of 18 aroma-related genes was performed to validate the transcriptome analysis. Our results identified key genes and pathways connected with the biosynthesis of aroma volatiles in white-fleshed pitaya. These results will be useful to dissect the genetic mechanism of fruit aroma in white-fleshed pitaya.

Background: Pitaya is an important economic fruit worldwide due to its numerous health benefits. A systematic understanding of the mechanism underlying flower development is essential to obtain higher fruit yield and quality. However, the genetic mechanism of flower development is not yet investigated in pitaya. Herein, a transcriptome analysis was performed to determine the transcriptional changes during flower development in red-flesh pitaya by utilizing nine different stages of flower development. Result: A total of 95,412 unigenes were generated with a mean length of 913 nt, and N50 value of 1878 nt. Comparative transcriptomic analysis showed many differentially expressed genes (DEGs) among the flower growth stages. Furthermore, an array of key DEGs were enriched in hormone signaling, transcription, carbohydrate transport, and energy production pathways. In particular, indole-3-acetic acid, abscisic acid, ethylene-responsive transcription factor, constans-like, teosinte branched 1/cycloidea/proliferating cell nuclear antigen factor, apetala1-like, agamous-like MADS-box protein, sepallata, growth-regulating factor, putative axial regulator yabby, leafy/floricaula homolog, and MYB gene-associated transcription factors displayed altered expression, suggesting their critical roles in floral organ development of pitaya. Besides, genes related to sugar synthesis, transportation, and utilization mediate flower growth regulation in pitaya. Eleven genes were selected to perform qRT-PCR analysis to verify the results of the RNA sequencing. Conclusions: Our results provide important insights into the transcriptional regulation of pitaya flower development. These data resources will be a cornerstone for future research that aims at exploring the genetic control of flower development in pitaya. How to cite: Wu Z, Huang L, Huang F, et al. Temporal transcriptome analysis provides molecular insights into flower development in red-flesh pitaya. Electron J Biotechnol 2022;58 https://doi.org/10.1016/j.ejbt. (c) 2022 Pontificia Universidad Catolica de Valparaiso. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

本文对农业农村部南宁火龙果种质资源圃从我国广西、广东、海南、福建、上海、云南、贵州、台湾等省(区)以及越南和以色列等地收集引进的359份资源进行鉴定分析,将相关资源数据通过建立数据库形式进行共享应用.火龙果种质资源数据库基于B/S三层网络架构,采用ASP.NET和SQL Server2008数据库技术和领域驱动模式进行开发.系统录入各火龙果种质资源相关数据,包括基本信息、植物学性状、农艺性状、果实品质等,系统具有数据可视化管理、检索、图片管理等功能.数据库的构建与应用,旨在实现火龙果种质资源信息化、规范化、标准化管理,提升火龙果种质资源信息共享利用率,为火龙果育种和产业发展提供助力.

以"紫龙"与"武鸣-4"火龙果及其杂交后代为试材,测定亲本及其杂交后代果实的主要性状,并对其遗传倾向进行分析.结果表明:单果质量、果形指数、皮厚、可食率和可溶性固形物含量呈连续变异,属数量性状遗传.单果质量遗传传递力低,变异系数大,整体呈趋小回归.果形指数、皮厚、可食率和可溶性固形物含量表现较高的遗传传递力.果形指数呈超高亲遗传趋势.可溶性固形物含量表现一定的杂交优势.杂交后代果肉颜色分离出紫红色、白色、红白双色及粉色4种类型,分别占41.63％、30.62％、15.79％和11.96％.果肉风味分离为甜、清甜、淡味或稍甜、蜜甜及甜带微酸,分别占39.23％、33.97％、10.53％、9.09％,7.18％.

对火龙果种质资源花表型性状的多样性及其与结果性状的相关性进行观察分析.结果表明:火龙果种质资源花盛开时的柱头与花药相对位置、柱头打开程度、花粉量、花的香气4个描述性状的Simpson指数为0.224～0.604,花朵长度、花冠直径、柱头与花药高度差、柱头裂条长度4个数量性状的遗传变异系数在0.08～0.96之间,存在着极为丰富的遗传多样性;火龙果自然坐果率、果实大小、商品果率与花盛开时的表型性状呈显著相关性,花盛开时柱头与花药相对位置和高度差、柱头裂条长度、花粉量等性状与自然坐果率和果实大小有密切相关性,是选育种中需要考量的重要指标.

以番荔枝不同组织样品为材料,通过基因文库筛选,利用RT-PCR技术克隆出1个1227 bp的基因,命名为AT-SWEET16-1,该基因编码408个氨基酸,该氨基酸序列在N端以α螺旋形成THB结构域.生物信息学分析结果表明,该蛋白分子量为44.8 kDa,等电点为8.87.进化分析结果发现其与海枣(Phoenix dactylifera)相类聚.qRT-PCR分析结果表明,该基因在植株的根、茎、嫩叶、老叶、花蕾、花苞、幼果、成熟果中均有表达,AT-SWEET16-1基因在不同组织中的表达量依次是:成熟果>茎>根>花蕾>幼果>老叶>嫩叶;该基因在不同果实发育阶段中的表达情况为:在果实不同发育阶段,果柄中的表达量最高,果肉、果皮中则相对较低,种子中最低;但果实成熟期该基因在果柄、果肉中的表达量最高.原位杂交实验观察发现,基因表达位置为果柄韧皮部、果肉细胞膜间,结合基因表达分析结果,预示该基因在植株糖分积累与转运等方面起到一定的作用.