Introduction: The color of Clausena lansium L. Skeels cv. Jixin fruit peel is brown (BP), while the mutant cv. Zijin had purple fruit peels (PP). The coloration of the peels was attributed to significant differences in chlorophyll, carotenoid, and anthocyanin content between BP and PP.Methods: This study investigates the biosynthetic metabolic activities in the brown and purple peels of Clausena lansium L. Skeels using metabolomics and transcriptomics. It aims to identify metabolic pathways and differentially expressed genes related to flavonoids and anthocyanins biosynthesis.Results: The PP (purple peel) has higher levels of a-carotene and b-carotene but lower levels of chlorophyll a, chlorophyll b, and lutein compared to BP. Zeaxanthin was absent from both peels, suggesting that the b-carotene hydroxylase enzyme is not active. Both peels contain delphinidin-based (Dp) and cyanidin-based (Cy) anthocyanins, but not pelargonidin-based (Pg). The total anthocyanin content and the Dp/Cy ratio are higher in PP than in BP. The delphinidin, cyanidin, and mallow derivatives in the PP were significantly higher than in the BP. The increase of total anthocyanin content and Dp/Cy ratio may be the main reason for the peel color changing from brown to purple. The significant increase of F3H expression in purple peels suggested a higher efficiency of catalyzing the conversion of naringenin into dihydroflavonols in the PP, leading to the higher content of total anthocyanin. Despite the significant increase of FLS expression in PP, the contents of kaempferol, quercetin, and myricetin significantly decreased, suggesting that the increase of FLS expression did not lead to an increase in flavonol biosynthesis.Discussion: The competition between F3’H and F3’5’H may determine the ratio of Dp/Cy, the higher levels of F3’H, F3’5’H, and UFGT expression, lead to the increase accumulation of total anthocyanin and Dp/Cy in PP. The deficiency of Pg in both peels resulted from the substrate specificity of the DFR enzyme. The research also describes the transition in color from BP to PP and details of the biosynthetic pathways for carotenoids and anthocyanins, elucidating the molecular processes underlying anthocyanin production.

Red fruit peel is an attractive target for pineapple breeding. Various pineapple accessions with distinct red coloration patterns exist; however, the precise molecular mechanism accounting for these differences remains unknown, which hinders the pineapple breeding process from combining high fruit quality with red peel. In this study, we characterized a transcription factor, AcMYB266, which is preferentially expressed in pineapple peel and positively regulates anthocyanin accumulation. Transgenic pineapple, Arabidopsis, and tobacco plants overexpressing AcMYB266 exhibited significant anthocyanin accumulation. Conversely, transient silencing of this gene led to decreased anthocyanin accumulation in pineapple red bracts. In-depth analysis indicated that variations of AcMYB266 sequences in the promoter instead of the protein-coding region seem to contribute to different red coloration patterns in peels of three representative pineapple varieties. In addition, we found that AcMYB266 was located in a cluster of four MYB genes exclusive to and conserved in Ananas species. Of this cluster, each was proved to regulate anthocyanin synthesis in different pineapple tissues, illustrating an interesting case of gene subfunctionalization after tandem duplication. In summary, we have characterized AcMYB266 as a key regulator of pineapple red fruit peel and identified an MYB cluster whose members were subfunctionalized to specifically regulate the red coloration of different pineapple tissues. The present study will assist in establishing a theoretical mechanism for pineapple breeding for red fruit peel and provide an interesting case for the investigation of gene subfunctionalization in plants.

Mangoes (Mangifera indica L.) are an important kind of perennial fruit tree, but their biochemical testing method and transformation technology were insufficient and had not been rigorously explored. The protoplast technology is an excellent method for creating a rapid and effective tool for transient expression and transformation assays, particularly in plants that lack an Agrobacterium-mediated plant transformation system. This study optimized the conditions of the protoplast isolation and transformation system, which can provide a lot of help in the gene expression regulation study of mango. The most beneficial protoplast isolation conditions were 150 mg/mL of cellulase R-10 and 180 mg/mL of macerozyme R-10 in the digestion solution at pH 5.6 and 12 h of digestion time. The 0.16 M and 0.08 M mannitol in wash solution (WI) and suspension for counting (MMG), respectively, were optimal for the protoplast isolation yield. The isolated leaf protoplasts (~5.4 × 10⁵ cells/10 mL) were transfected for 30 min mediated by 40% calcium-chloride-based polyethylene glycol (PEG)-4000-CaCl₂, from which 84.38% of the protoplasts were transformed. About 0.08 M and 0.12 M of mannitol concentration in MMG and transfection solutions, respectively, were optimal for protoplast viability. Under the florescence signal, GFP was seen in the transformed protoplasts. This showed that the target gene was successfully induced into the protoplast and that it can be transcribed and translated. Experimental results in this paper show that our high-efficiency protoplast isolation and PEG-mediated transformation protocols can provide excellent new methods for creating a rapid and effective tool for the molecular mechanism study of mangoes.

Chlorophyll and heme are essential molecules for photosynthesis and respiration, which are competing branches of the porphyrin metabolism pathway. Chlorophyll and heme balance regulation is very important for the growth and development of plants. The chimeric leaves of Ananas comosus var. bracteatus were composed of central photosynthetic tissue (PT) and marginal albino tissue (AT), which were ideal materials for the study of porphyrin metabolism mechanisms. In this study, the regulatory function of ALA content on porphyrin metabolism (chlorophyll and heme balance) was revealed by comparing PT and AT, 5-Aminolevulinic Acid (ALA) exogenous supply, and interference of hemA expression. The AT remained similar in porphyrin metabolism flow level to the PT by keeping an equal ALA content in both tissues, which was very important for the normal growth of the chimeric leaves. As the chlorophyll biosynthesis in AT was significantly inhibited, the porphyrin metabolism flow was directed more toward the heme branch. Both tissues had similar Mg²⁺ contents; however, Fe²⁺ content was significantly increased in the AT. The chlorophyll biosynthesis inhibition in the white tissue was not due to a lack of Mg²⁺ and ALA. A 1.5-fold increase in ALA content inhibited chlorophyll biosynthesis while promoting heme biosynthesis and hemA expression. The doubling of ALA content boosted chlorophyll biosynthesis while decreasing hemA expression and heme content. HemA expression interference resulted in a higher ALA content and a lower chlorophyll content, while the heme content remained at a relatively low and stable level. Conclusively, a certain amount of ALA was important for the stability of porphyrin metabolism and the normal growth of plants. The ALA content appears to be able to regulate chlorophyll and heme content by bidirectionally regulating porphyrin metabolism branch direction.

The restorative effects of various environmental factors within urban forests on physical and mental health exhibit significant differences. Specifically, vegetation types and topographical slope positions are key elements contributing to the environmental heterogeneity of urban forests. However, there is a lack of studies that have concurrently examined the health restoration effects of both factors. This study conducted an empirical experiment on university students in urban forests during the autumn season, investigating the effects of different vegetation types and slope positions on physiological and psychological restoration, and identifying the key environmental factors contributing to these effects. The results show the following: (1) Urban forests with different vegetation types exhibit varying restorative effects, with coniferous forests offering greater physiological restoration benefits than coniferous–broadleaf mixed forests. (2) Slope position affects both physiological and psychological restoration. In coniferous forests, the restorative effects on physical and mental health are greater at the top and midslope positions compared to the bottom slope position; in coniferous–broadleaf mixed forests, the best physiological restoration effects occur at the midslope position. (3) The key environmental factors influencing physiological restoration in urban coniferous forests are panoramic green coverage and elevation. (4) In urban coniferous–broadleaf mixed forests, temperature, humidity, and wind speed are the key factors affecting physiological restoration. This study reveals the restorative differences in urban forests under different vegetation types and slope positions, identifies the key environmental factors influencing health restoration, and provides a theoretical basis for further research on the impact of urban forests on human health. Future urban forest layout and design should fully consider the characteristics of different slope positions, optimize microclimate regulation, and maximize their role in promoting public health.

To achieve the transition of rural areas from traditional to modern, the visualization of rural landscape data and feature evaluations are essential. Landscape character assessment (LCA) is a well-established tool that was developed to assess and understand rural landscape features. In recent years, drones have become increasingly attractive for various applications and services due to their low costs and relative ease of operation. Unlike most previous studies that relied solely on drone-based remote sensing or visual esthetic evaluations, this study proposes an innovative assessment method based on landscape characteristic assessment (LCA) and oblique drone photography technology, supported by specific data and survey results. These include various landscape metrics, such as the Shannon diversity index (SHDI), Shannon evenness index (SHEI), vegetation coverage, landscape character zoning, and delineations of various ecologically sensitive areas. This method was applied to study Zhanqi Village in Chengdu, Sichuan Province, China and revealed some unique characteristics of this village. By categorizing and describing the landscape features, the study makes judgments and decisions about them. This is a beneficial attempt to apply the scientific methods of landscape assessments to the production management of aerial drone surveys. This method provides a comprehensive framework for evaluating rural landscape features and demonstrates that the combination of LCA and oblique drone photography technology is feasible for rural landscape research. Additionally, this study emphasizes the need for further research to explore the potential application of this method in continuously evolving urban and rural environments in the future.