Passion fruit (Passiflora edulis Sims) can be divided into yellow and purple varieties. However, information about coloration and fruit quality between the two varieties is limited. To reveal the underlying mechanism of color formation in this fruit, a combined analysis of the metabolome and transcriptome was conducted in this study. The results showed that most of the evaluated flavonols, anthocyanins, and flavanols were significantly upregulated in purple fruit compared to their levels in yellow fruit. Flavonoid and flavonoid carbonoside accumulation was markedly higher in yellow fruit than in purple fruit. The accumulation of organic acids, phenolic acids, lipids, sugars, and lignans was significantly different in the yellow and purple varieties. These results were consistent with the results from the RNA-Seq profile. This study will enable us to identify genes for targeted genetic engineering to improve the nutritional and market value of passion fruit. In addition, the peel and pulp of passion fruit contained certain health-promoting compounds, highlighting the potential application of passion fruit as a functional food and providing direction for future breeding programs and production.

Wampee is one of the characteristic fruits in southern China, and its brittle and thin skin can easily be damaged. In this study, principal components analysis (PCA) and minimum noise fraction (MNF) analysis were carried out on the two wampee varieties by hyperspectral imaging technology, and 680nm was determined to be the optimal characteristic wavelength. The accurate recognition rate obtained from PCA algorithm for wampee samples of two varieties was about 83.75%, and that obtained from MNF algorithm for two variety samples was 85%. It was indicated that the wampee damaged can be identified more accurately and effectively by MNF based on hyperspectral imaging technology

Abiotic stress is the focus of passion fruit research since it harms the industry, in which high temperature is an important influencing factor. Dof transcription factors (TFs) act as essential regulators in stress conditions. TFs can protect against abiotic stress via a variety of biological processes. There is yet to be published a systematic study of the Dof (PeDof) family of passion fruit. This study discovered 13 PeDof family members by using high-quality genomes, and the members of this characterization were identified by bioinformatics. Transcriptome sequencing and qRT-PCR were used to analyze the induced expression of PeDofs under high-temperature stress during three periods, in which PeDof-11 was significantly induced with high expression. PeDof-11 was then chosen and converted into yeast, tobacco, and Arabidopsis, with the findings demonstrating that PeDof-11 could significantly respond to high-temperature stress. This research lays the groundwork for a better understanding of PeDof gene regulation under high-temperature stress.

High temperature in summer is an unfavorable factor for passion fruit (Passiflora edulis), which can lead to restricted growth, short flowering period, few flower buds, low fruit setting rate, severe fruit drop, and more deformed fruit. To explore the molecular physiology mechanism of passion fruit responding to high-temperature stress, we use ‘Zhuangxiang Mibao’, a hybrid passion fruit cultivar, as the test material. Several physiological indicators were measured and compared between high-temperature (average temperature 38 °C) and normal temperature (average temperature 25 °C) conditions, including photosynthesis, chlorophyll fluorescence parameters, peroxidase activity (POD), superoxide dismutase activity (SOD) and malondialdehyde content. We performed RNA-seq analysis combined with biochemistry experiment to investigate the gene and molecular pathways that respond to high-temperature stress. The results showed that some physiological indicators in the high-temperature group, including the net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, and the maximum chemical quantum yield of photosystemII (PSII), were significantly lower than those of the control group. Malondialdehyde content was substantially higher than the control group, while superoxide dismutase and superoxide dismutase activities decreased to different degrees. Transcriptome sequencing analysis showed that 140 genes were up-regulated and 75 genes were down-regulated under high-temperature stress. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation analysis of differentially expressed genes revealed many metabolic pathways related to high-temperature stress. Further investigation revealed that 30 genes might be related to high-temperature stress, such as chlorophyllide a oxygenase (CAO), glutathione (GSH), WRKY transcription factors (WRKY), and heat shock protein (HSP), which have also been reported in other species. The results of real-time fluorescence quantitative PCR and RNA-seq of randomly selected ten genes are consistent, which suggests that the transcriptome sequencing results were reliable. Our study provides a theoretical basis for the mechanism of passion fruit response to high-temperature stress. Also, it gives a theoretical basis for the subsequent breeding of new heat-resistant passion fruit varieties.

Complex metabolic components in mango leaves lead to high difficulty in RNA extraction. In order to improve the quality of total RNA extraction, on the basis of the existing methods reported in the literature, an RNA extraction method combining acetone washing liquid nitrogen abrasive material with 0.3 mol/L lithium chloride (LiCl) solution and 2 times the volume of anhydrous ethanol as the second precipitator was developed. The experimental results showed that the improved method significantly reduced the amount of impurity precipitation in the RNA extraction process. The electrophoretic bands of total RNA extracted were complete. The absorbance ratio of OD260/280 was about 1.9, and the average was 329.8 g/g FW±11.2 g/g FW. Further validation experiments of RNA reverse transcription and the polymorphic amplification of double-stranded cDNA related sequences (RAP-PCR) obtained clear polymorphic bands, showing that the total RNA from mango leaves had high quality and was suitable for molecular biology experiments.

High temperature in summer is an unfavorable factor for passion fruit (Passiflora edulis), which can lead to restricted growth, short flowering period, few flower buds, low fruit setting rate, severe fruit drop, and more deformed fruit. To explore the molecular physiology mechanism of passion fruit responding to high-temperature stress, we use Zhuangxiang Mibao, a hybrid passion fruit cultivar, as the test material. Several physiological indicators were measured and compared between high-temperature (average temperature 38℃) and nonmoral temperature (average temperature 25℃) conditions, including photosynthesis, chlorophyll fluorescence parameters, POD, SOD activity and malondialdehyde content. We performed RNA-seq analysis combined with biochemistry experiment to investigate the gene and molecular pathways that respond to high-temperature stress. The results showed that some physiological indicators in the high-temperature group, including the net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, and the maximum chemical quantum yield of PSⅡ, were significantly lower than those of the control group. Malondialdehyde content was substantially higher than the control group, while superoxide dismutase and superoxide dismutase activities decreased to different degrees. Transcriptome sequencing analysis showed that 140 genes were up-regulated and 75 genes were down-regulated under high-temperature stress. GO and KEGG annotation analysis of differentially expressed genes revealed many metabolic pathways related to high-temperature stress. Further investigation revealed that 30 genes might be related to high-temperature stress, such as CAO, GSH, WRKY, and HSP, which have also been reported in other species. The results of real-time fluorescence quantitative PCR and RNA-seq of randomly selected ten genes are consistent, which suggests that the transcriptome sequencing results were reliable. Our study provides a theoretical basis for the mechanism of passion fruit response to high-temperature stress. Also, it gives a theoretical basis for the subsequent breeding of new heat-resistant passion fruit varieties.