Sex-biased genes and metabolites explain morphologically sexual dimorphism and reproductive costs in Salix paraplesia catkins

Polystyrene Nanoplastics Compromise the Nutritional Value of Radish (Raphanus sativus L.)

The accumulation of nanoplastics (NPs) in crops has drawn global attention due to their potential exacerbation in human health through food chain transfer. The present study investigated the distribution, accumulation, and phytotoxicity of polystyrene (PS) NPs in radish and evaluated the potential risks of PS NPs to human health via a simulated INFOGEST model. PS NPs were mainly accumulated in the cortex and xylem of radish roots and primarily accumulated within the peels via direct adsorption onto tuber surfaces. Transcriptomic and metabolomic analyses revealed that exposure to PS NPs triggered plant defense systems by upregulating gene expression and metabolites involved in flavonoid biosynthesis as well as starch and sucrose metabolisms. However, the downregulation of genes associated with plant hormone signal transduction, as well as the biosynthesis of glucosinolates (the most valued compounds contributing to radish nutrition and flavor), and amino acids reduced crop yield and quality. Importantly, the investigations using a simulated INFOGEST model showed that PS NPs significantly reduced bioaccessibilities or index of nutritional quality (INQ) of amino acids and glucosinolates in the digesta of radish fruits, thereby compromising the nutritional value of radish. These findings further our understanding of the negative effects of NPs-contaminated crops on human digestive tract health.

Soil cadmium pollution elicits sex-specific plant volatile emissions in response to insect herbivory in eastern cottonwood Populus deltoides

Soil heavy metal pollution is a major abiotic stressor frequently encountered by plants in conjunction with other biotic stresses like insect herbivory. Yet, it remains largely unexplored how soil metal pollution and insect herbivory act together to influence emissions of plant volatile organic compounds (VOCs), which mediate multiple ecological functions and play crucial roles in atmospheric processes. Here, we assessed the individual and combined effects of soil cadium (Cd) pollution and insect herbivory by Clostera anachoreta on VOC emissions from the seedlings of eastern cottonwood Populus deltoides, and whether these effects depend on plant sex. We found that plant sex notably influenced VOC emission and altered blend compositions, with male seedlings emitting higher amounts of monoterpenes, sesquiterpenes, homoterpenes and green leaf volatiles (GLVs) than females. Soil Cd exposure significantly increased emissions of monoterpenes, GLVs, and nitrogenous VOCs in males but not in females. Comparatively, larval feeding exerted the strongest effects on VOC emissions and their composition, albeit to varying extent between males and females, and among different VOC classes. Importantly, Cd exposure amplified herbivore-induced VOC emissions in males. For instance, under both Cd and herbivory conditions, male seedlings showed a 68.1-fold increase in nitrogenous VOC emissions, almost twice the combined effects of Cd (8.7-fold) and herbivory (26.3-fold). Taken together, these results suggest that soil metal pollution can boost herbivore-induced VOC emissions in a sex-specific manner, with potential implications for ecological interactions and atmospheric processes.

Molecular Evidence of CeO2 Nanoparticle Modulation of ABA and Genes Containing ABA-Responsive Cis-Elements to Promote Rice Drought Resistance

Cerium dioxide nanoparticles (CeO2 NPs) have enzyme-like properties and scavenge excess ROS induced by stressors such as drought. However, the underlying molecular mechanisms by which CeO2 NPs enhance drought resistance are unknown. In this work, both foliar application and soil injection of CeO2 NPs were used to rice seedlings under a 30 day moderate drought (40% soil relative moisture). Foliar application of 4 mg of CeO2 NPs per pot reduced excess reactive oxygen species and abscisic acid (ABA) in rice leaves, thereby maintaining chloroplast structural integrity and photosynthetic output, ultimately increasing drought-stressed rice biomass by 31.3%. Genes associated with photosynthesis and ribosome activity provided the foundation by which CeO2 NPs enhanced rice drought resistance. Importantly, these genes were tightly regulated by ABA due to the large number of abscisic acid responsive elements in their promoter regions. CeO2 NPs also upregulated the expression of soluble sugar and fatty acid synthesis associated genes in drought-stressed rice, thereby contributing to osmotic balance and membrane lipid stability. These results highlight the potential of CeO2 NPs to enhance rice photosynthesis and drought-resistant biomolecule accumulation by regulating ABA-dependent responses. This work provides further evidence demonstrating nanomaterials have great potential to sustainably promote stress resistance and climate resilient crops.

Accumulation characteristics of plant flavonoids and effects of cultivation measures on their biosynthesis: A review

Flavonoids, a kind of secondary metabolites with both edible, medicinal and antioxidant purposes, could be widely used in food, drug processing, forest products, chemical industry and many other fields. Flavonoid production in plant organs were influenced by numerous internal and external factors at various stages, leading to differential gene expression and transcription factors activity. This study reviews the characteristics of major flavonoids categories, their distribution and accumulation in different plant parts and analyzing their molecular mechanisms. The results showed that: (1) Flavonoids exhibited wide distribution in all parts of the plants, with higher concentrations found in shoots system compared to roots sytem, across most species (predominantly accumulated in leaves and flowers). Plant sex, specific growth and development stages are both impacting indicators; (2) Cultivation methods and abiotic stress could affect plants flavonoid biosynthesis, while inappropriate physical treatments and cultivation methods induced stress in plants, prompting the activation of antioxidant mechanisms for flavonoid synthesis as a defence strategy via indirect pathways; (3) Various key genes and transcription factors collaboratively influenced key enzymes activities and regulate flavonoid biosynthesis, forming a complex regulatory network among these genes and transcription factors; (4) Further studies are required to elucidate whether flavonoid synthesis under various cultivation measures follows direct or indirect pathways. Furthermore, exploring methods for flavonoid biosynthesis and accumulation in specific organs or tissues, as well as identifying plant tissues and microorganisms with high efficiency in flavonoid biosynthesis, is essential for achieving targeted cultivation of plants and quantitative flavonoid production.

Comparative proteomic analysis of papaya bud flowers reveals metabolic signatures and pathways driving hermaphrodite development

Papaya (Carica papaya) is a trioecious species with female, male, and hermaphrodite plants. Given the sex segregation, selecting hermaphroditic plants is vital for orchard establishment due to their greater commercial value. However, selecting hermaphrodite plants through sexing is laborious and costly. Moreover, environmental stressors can exacerbate the issue by potentially inducing abnormal flower development, thus affecting fruit quality. Despite these challenges, the molecular mechanisms governing sex development in papaya remain poorly understood. Thus, this study aimed to identify proteins associated with sex development in female and hermaphrodite flowers of papaya through comparative proteomic analysis. Proteins from flower buds at the early and late developmental stages of three papaya genotypes (UENF-CALIMAN 01, JS12, and Sunrise Solo 72/12) were studied via proteomic analysis via the combination of the shotgun method and nanoESI-HDMSE technology. In buds at an early stage of development, 496 (35.9%) proteins exhibited significantly different abundances between sexes for the SS72/12 genotype, 139 (10%) for the JS12 genotype, and 165 (11.9%) for the UC-01 genotype. At the final stage of development, there were 181 (13.5%) for SS72/12, 113 (8.4%) for JS12, and 125 (9.1%) for UC-01. The large group of differentially accumulated proteins (DAPs) between the sexes was related to metabolism, as shown by the observation of only the proteins that exhibited the same pattern of accumulation in the three genotypes. Specifically, carbohydrate metabolism proteins were up-regulated in hermaphrodite flower buds early in development, while those linked to monosaccharide and amino acid metabolism increased during late development. Enrichment of sporopollenin and phenylpropanoid biosynthesis pathways characterizes hermaphrodite samples across developmental stages, with predicted protein interactions highlighting the crucial role of phenylpropanoids in sporopollenin biosynthesis for pollen wall formation. Most of the DAPs played key roles in pectin, cellulose, and lignin synthesis and were essential for cell wall formation and male flower structure development, notably in the pollen coat. These findings suggest that hermaphrodite flowers require more energy for development, likely due to complex pollen wall formation. Overall, these insights illuminate the molecular mechanisms of papaya floral development, revealing complex regulatory networks and energetic demands in the formation of male reproductive structures.

Study on peanut protein oxidation and metabolomics/proteomics analysis of peanut response under hypoxic/re-aeration storage

To better understand the effect of oxygen levels in the storage environment on peanut protein oxidation and explore the mechanism, the functional properties and the oxidation degree of peanut proteins extracted from peanuts under conventional storage (CS), nitrogen modified atmosphere storage (NS, hypoxic) and re-aeration storage (RS) were investigated. Metabolomics and proteomics were employed to analyze peanut's response to hypoxic/re-aeration storage environment. The results showed that NS retarded the decline of the functional properties and the oxidation of peanut proteins, while the process were accelerated after re-aeration. That was the result of the metabolic changes of peanuts under different storage environments. The omics results presented the decreased (NS)/increased (RS) levels of the antioxidant-related proteins acetaldehyde dehydrogenase and glutathione S-transferase, and the inhibition (NS)/activation (RS) of metabolic pathways such as the TCA cycle and the pentose phosphate pathway. This study provided a reference for the re-aeration storage of other agricultural products.

Positive selection and relaxed purifying selection contribute to rapid evolution of male-biased genes in a dioecious flowering plant

Sex-biased genes offer insights into the evolution of sexual dimorphism. Sex-biased genes, especially those with male bias, show elevated evolutionary rates of protein sequences driven by positive selection and relaxed purifying selection in animals. Although rapid sequence evolution of sex-biased genes and evolutionary forces have been investigated in animals and brown algae, less is known about evolutionary forces in dioecious angiosperms. In this study, we separately compared the expression of sex-biased genes between female and male floral buds and between female and male flowers at anthesis in dioecious Trichosanthes pilosa (Cucurbitaceae). In floral buds, sex-biased gene expression was pervasive, and had significantly different roles in sexual dimorphism such as physiology. We observed higher rates of sequence evolution for male-biased genes in floral buds compared to female-biased and unbiased genes. Male-biased genes under positive selection were mainly associated with functions to abiotic stress and immune responses, suggesting that high evolutionary rates are driven by adaptive evolution. Additionally, relaxed purifying selection may contribute to accelerated evolution in male-biased genes generated by gene duplication. Our findings, for the first time in angiosperms, suggest evident rapid evolution of male-biased genes, advance our understanding of the patterns and forces driving the evolution of sexual dimorphism in dioecious plants.

An integrated transcriptome and metabolome analysis reveals the gene network regulating flower development in Pogostemon cablin

Pogostemon cablin is a well-known protected species widely used in medicine and spices, however the underlying molecular mechanisms and metabolite dynamics of P. cablin flower development remain unclear due to the difficulty in achieving flowering in this species. A comparison of the transcriptome and widely targeted metabolome during P. cablin flower development was first performed in this study. Results showed that a total of 13,469 differentially expressed unigenes (DEGs) and 371 differentially accumulated metabolites (DAMs) were identified. Transcriptomic analysis revealed that the DEGs were associated with starch and sucrose metabolism, terpenoid biosynthesis and phenylpropanoid biosynthesis. Among these DEGs, 75 MIKC-MADS unigenes were associated with the development of floral organs. Gibberellins (GAs), auxin, and aging signaling might form a cross-regulatory network to regulate flower development in P. cablin. According to the metabolic profile, the predominant DAMs were amino acids, flavonoids, terpenes, phenols, and their derivatives. The accumulation patterns of these predominant DAMs were closely associated with the flower developmental stage. The integration analysis of DEGs and DAMs indicated that phenylpropanoids, flavonoids, and amino acids might be accumulated due to the activation of starch and sucrose metabolism. Our results provide some important insights for elucidating the reproductive process, floral organ, and color formation of P. cablin flowers at the molecular level. These results will improve our understanding of the molecular and genetic mechanisms involved in the floral development of P. cablin.

Differences in phytohormone and flavonoid metabolism explain the sex differences in responses of Salix rehderiana to drought and nitrogen deposition

Due to global warming and the increase in nitrogen oxide emissions, plants experience drought and nitrogen (N) deposition. However, little is known about the acclimation to drought and N deposition of Salix species, which are dioecious woody plants. Here, an investigation into foliar N deposition combined with drought was conducted by assessing integrated phenotypes, phytohormones, transcriptomics, and metabolomics of male and female Salix rehderiana. The results indicated that there was greater transcriptional regulation in males than in females. Foliar N deposition induced an increase in foliar abscisic acid (ABA) levels in males, resulting in the inhibition of stomatal conductance, photosynthesis, carbon (C) and N accumulation, and growth, whereas more N was assimilated in females. Growth as well as C and N accumulation in drought-stressed S. rehderiana females increased after N deposition. Interestingly, drought decreased flavonoid biosynthesis whereas N deposition increased it in females. Both drought and N deposition increased flavonoid methylation in males and glycosylation in females. However, in drought-exposed S. rehderiana, N deposition increased the biosynthesis and glycosylation of flavonoids in females but decreased glycosylation in males. Therefore, foliar N deposition affects the growth and drought tolerance of S. rehderiana by altering the foliar ABA levels and the biosynthesis and modification of flavonoids. This work provides a basis for understanding how S. rehderiana may acclimate to N deposition and drought in the future.

Acetic acid enhances drought tolerance more in female than in male willows

Drought is an important stress factor that limits plant growth and development. Female willows generally display stronger drought tolerance than males. The application of exogenous acetic acid (AA) has emerged as an efficient and eco-friendly approach to facilitate drought tolerance in willows. However, whether AA exerts sexually different effects on willows remains undefined. In this study, we comprehensively performed morphological and physiological analyses on three willow species, Salix rehderiana, Salix babylonica, and Salix matsudana, to investigate the sexually different responses to drought and AA. The results indicated that willow females were more drought-tolerant than males. AA application effectively enhanced willows' drought tolerance, and females applied with AA displayed greater root distribution and activity, stronger osmotic and antioxidant capacity and photosynthetic rate but less reactive oxygen species, or abscisic acid-mediated stomatal closure than males. In addition, AA application enhanced the jasmonic acid signaling pathway in females but inhibited it in males, conferring stronger drought defense capacity in female willows than in males. Overall, AA application improves drought tolerance more in female than in male willows, further enlarging the sexual differences in willows under drought-stressed conditions.

Genetic mapping of sexually dimorphic volatile and non-volatile floral secondary chemistry of a dioecious willow

Secondary chemistry often differs between sexes in dioecious plant species, a pattern attributed to its possible role in the evolution and/or maintenance of dioecy. We used GC-MS to measure floral volatiles emitted from, and LC-MS to quantitate non-volatile secondary compounds contained in, female and male Salix purpurea willow catkins from an F2 family. Using the abundance of these chemicals, we then performed quantitative trait locus (QTL) mapping to locate them on the genome, identified biosynthetic candidate genes in the QTL intervals, and examined expression patterns of candidate genes using RNA-seq. Male flowers emitted more total terpenoids than females, but females produced more benzenoids. Male tissue contained greater amounts of phenolic glycosides, but females had more chalcones and flavonoids. A flavonoid pigment and a spermidine derivative were found only in males. Male catkins were almost twice the mass of females. Forty-two QTL were mapped for 25 chemical traits and catkin mass across 16 of the 19 S. purpurea chromosomes. Several candidate genes were identified, including a chalcone isomerase associated with seven compounds. A better understanding of the genetic basis of the sexually dimorphic chemistry of a dioecious species may shed light on how chemically mediated ecological interactions may have helped in the evolution and maintenance of dioecy.

Integrated transcriptome and plant growth substance profiles to identify the regulatory factors involved in floral sex differentiation in Zanthoxylum armatum DC

Zanthoxylum armatum is a prominent plant for food industries. Its male flowers often occur in gynogenesis plants; however, the potential mechanism remains poorly understood. Herein, a total of 26 floral sex differentiation stages were observed to select four vital phases to reveal key factors by using RNA-seq, phytohormones and carbohydrates investigation. The results showed that a selective abortion of stamen or pistil primordia could result in the floral sex differentiation in Z. armatum. Carbohydrates might collaborate with cytokinin to effect the male floral differentiation, whereas female floral differentiation was involved in SA, GA₁, and ABA biosynthesis and signal transduction pathways. Meanwhile, these endogenous regulators associated with reproductive growth might be integrated into ABCDE model to regulate the floral organ differentiation in Z. armatum. Furthermore, the 21 crucial candidates were identified in co-expression network, which would contribute to uncovering their roles in floral sex differentiation of Z. armatum in further studies. To the best of our knowledge, this study was the first comprehensive investigation to link floral sex differentiation with multi-level endogenous regulatory factors in Z. armatum. It also provided new insights to explore the regulatory mechanism of floral sex differentiation, which would be benefited to cultivate high-yield varieties in Z. armatum.

A Selection of Reliable Reference Genes for Gene Expression Analysis in the Female and Male Flowers of Salix suchowensis

Salix is a dioecious plant. Research on the molecular regulation mechanism of male and female inflorescence differentiation and development is necessary to analyze sex differentiation in the willow and the underlying mechanisms of unisexual flower development. However, at present, there are no reference genes suitable for stable expression in the process of willow inflorescence development. In this study, Salix suchowensis was used as the research material, nine candidate reference genes (α-TUB1, α-TUB2, ACT, H2A, DnaJ, CDC2, GAPDH, TIP41, β-TUB) were selected, and qRT-PCR technology was used to detect the expression of each candidate reference gene in female and male flowers at different developmental stages and using five algorithms (geNorm, Normfinder, Delta Ct, BestKeeper, and RefFinder) to comprehensively evaluate the stability of candidate reference genes. The results showed that ACT and DnaJ were stably expressed in all samples and could be used as reference genes. In addition, the reliability of the screening results was further verified via an expression pattern analysis of the CFS gene that encodes flower specific transcription factor in different samples. The stable reference genes selected in this study provide the basis for future research on the expression analysis of functional genes related to the development of male and female flowers of S. suchowensis.