ETHYLENE-INSENSITIVE 3-LIKE 2 regulates β-carotene and ascorbic acid accumulation in tomatoes during ripening

Comparative transcriptome analysis of cucumber fruit tissues reveals novel regulatory genes in ascorbic acid biosynthesis

Ascorbic acid (AsA) is one of the most abundant natural antioxidants, and it is an important indicator of the nutritional value of cucumber fruit. The aim of this study was to elucidate the regulatory mechanism affecting AsA metabolism in cucumber fruit. In this study, the AsA content in the fruit of two cucumber cultivars (H28 and H105) was significantly higher in the exocarp and endocarp than in the mesocarp. To clarify the regulation of AsA in cucumber fruit, the transcriptomes of three fruit tissues (i.e., the exocarp, mesocarp, and endocarp) of two cucumber cultivars (H28 and H105) were sequenced. Transcriptomic profiling combined with transcription factors (TFs) and correlation analysis were performed to reveal that three genes, including CsaV3_5G014110 (phosphomannomutase, PMM), CsaV3_2G004170 (GDP-mannose-3', 5'-epimerase, GME) and CsaV3_5G006680 (dehydroascorbate reductase, DHAR), were expressed at higher level in the exocarp and endocarp than in the mesocarp. In both two cultivars, CsaV3_4G028360 (ethylene-responsive transcription factor, ERF) was negatively correlated with PMM and GME, and positively correlated with DHAR. CsaV3_6G042110 (ethylene-responsive transcription factor, ERF) was positively correlated with PMM and GME, and negatively correlated with DHAR. CsaV3_6G032360 (mitogen-activated protein kinase, MAPK) as positively correlated with PMM, GME and DHAR. These six genes are considered the key candidate genes for further research. This study provides insight for further study on the regulation of AsA biosynthesis in cucumber fruit and provide potential candidate genes for future genetic improvement of cucumber germplasm with enhanced AsA accumulation.

Integrative Analysis of Metabolome and Transcriptome of Carotenoid Biosynthesis Reveals the Mechanism of Fruit Color Change in Tomato (Solanum lycopersicum)

Tomato fruit ripening is accompanied by carotenoid accumulation and color changes. To elucidate the regulatory mechanisms underlying carotenoid synthesis during fruit ripening, a combined transcriptomic and metabolomic analysis was conducted on red-fruited tomato (WP190) and orange-fruited tomato (ZH108). A total of twenty-nine (29) different carotenoid compounds were identified in tomato fruits at six different stages. The abundance of the majority of the carotenoids was enhanced significantly with fruit ripening, with higher levels of lycopene; (E/Z)-lycopene; and α-, β- and γ-carotenoids detected in the fruits of WP190 at 50 and 60 days post anthesis (DPA). Transcriptome analysis revealed that the fruits of two varieties exhibited the highest number of differentially expressed genes (DEGs) at 50 DPA, and a module of co-expressed genes related to the fruit carotenoid content was established by WGCNA. qRT-PCR analysis validated the transcriptome result with a significantly elevated transcript level of lycopene biosynthesis genes (including SlPSY2, SlZCIS, SlPDS, SlZDS and SlCRTSO2) observed in WP190 at 50 DPA in comparison to ZH108. In addition, during the ripening process, the expression of ethylene biosynthesis (SlACSs and SlACOs) and signaling (SlEIN3 and SlERF1) genes was also increased, and these mechanisms may regulate carotenoid accumulation and fruit ripening in tomato. Differential expression of several key genes in the fruit of two tomato varieties at different stages regulates the accumulation of carotenoids and leads to differences in color between the two varieties of tomato. The results of this study provide a comprehensive understanding of carotenoid accumulation and ethylene biosynthesis and signal transduction pathway regulatory mechanisms during tomato fruit development.

Transcriptomic Analysis Reveals the Flavonoid Biosynthesis Pathway Involved in Rhizome Development in Polygonatum cyrtonema Hua

Polygonatum cyrtonema Hua (P. cyrtonema) rhizomes are rich in flavonoids and other secondary metabolites, exhibiting remarkable antioxidant, anti-tumor, and immunomodulatory effects. Polygonatum flavonoid-biosynthesis-related genes have been characterized already. However, a comprehensive overview of Polygonatum flavonoid biosynthesis pathways is still absent. To articulate the accumulation of the flavonoid biosynthesis pathways, we examined transcriptome changes using Illumina HiSeq from five different tissues and the RNA-seq of 15 samples had over 105 Gb of a clean base, generating a total of 277,955 unigenes. The cDNA libraries of the fruits (F), leaves (L), roots (R), stems (S), and rhizomes (T) of three-year-old P. cyrtonema plants generated 57,591, 53,578, 60,321, 51,530, and 54,935 unigenes. Comparative transcriptome analysis revealed that 379 differentially expressed genes (DEGs) were in the group of F _vs_ T, L _vs_ T, R _vs_ T, and S _vs_ T, and the transcripts of flavonoid-biosynthesis-related DEGs were principally enriched in rhizomes. In addition, combined with WGCNA and the FPKM of five tissues' transcription, nine differentially expressed transcription factor families (MYB, WRKY, AP2/ERF, etc.) were characterized in the red module, the red module positively correlated with rhizome flavonoid accumulation. Quantitative real-time PCR (qRT-PCR) further indicated that BZIP1, C3H31, ERF114, and DREB21 are differentially expressed in rhizomes, accompanied in rhizome development in P. cyrtonema. Therefore, this study provides a foundation for further research into uncovering the accumulation of flavonoid biosynthesis in the rhizomes of P. cyrtonema.

Overexpression of cassava melatonin receptor PMTR1 plays dual roles in development under light and dark conditions in Arabidopsis

KEY MESSAGE

MePMTR1 is involved in plant development and production as well as photosynthesis in plant. Melatonin is widely involved in plant growth and development as well as stress responses. Compared with the extending studies of melatonin in stress responses, the direct link between melatonin and plant development in the whole stages remains unclear. With the identification of phytomelatonin receptor PMTR1 in plants, melatonin signalling is becoming much clearer. However, the function of MePMTR1 in tropical crop cassava remains elusive. In this study, we found that overexpression of MePMTR1 showed larger biomass than wild type (WT), including higher number and area of leaves, weight, and accompanying with higher photosynthetic efficiency. Consistently, exogenous melatonin accelerated photosynthetic rate in Arabidopsis. In addition, MePMTR1-overexpressed plants exhibited more resistance to dark-induced senescence compared with WT, demonstrated by higher chlorophyll, lower hydrogen peroxide and superoxide content. In summary, this study illustrated that melatonin and its receptor regulate growth, development and senescence in plants, highlighting the potential application of melatonin and its receptor in improving crop yield and photosynthesis.

Integrated analysis of metabolome, transcriptome, and bioclimatic factors of Acer truncatum seeds reveals key candidate genes related to unsaturated fatty acid biosynthesis, and potentially optimal production area

BACKGROUND

Lipids found in plant seeds are essential for controlling seed dormancy, dispersal, and defenses against biotic and abiotic stress. Additionally, these lipids provide nutrition and energy and are therefore important to the human diet as edible oils. Acer truncatum, which belongs to the Aceaceae family, is widely cultivated around the world for its ornamental value. Further because its seed oil is rich in unsaturated fatty acids (UFAs)- i.e. α-linolenic acid (ALA) and nervonic acid (NA)- and because it has been validated as a new food resource in China, the importance of A. truncatum has greatly risen. However, it remains unknown how UFAs are biosynthesized during the growth season, to what extent environmental factors impact their content, and what areas are potentially optimal for their production.

RESULTS

In this study, transcriptome and metabolome of A. truncatum seeds at three representative developmental stages was used to find the accumulation patterns of all major FAs. Cumulatively, 966 metabolites and 87,343 unigenes were detected; the differential expressed unigenes and metabolites were compared between stages as follows: stage 1 vs. 2, stage 1 vs. 3, and stage 2 vs. 3 seeds, respectively. Moreover, 13 fatty acid desaturases (FADs) and 20 β-ketoacyl-CoA synthases (KCSs) were identified, among which the expression level of FAD3 (Cluster-7222.41455) and KCS20 (Cluster-7222.40643) were consistent with the metabolic results of ALA and NA, respectively. Upon analysis of the geographical origin-affected diversity from 17 various locations, we found significant variation in phenotypes and UFA content. Notably, in this study we found that 7 bioclimatic variables showed considerable influence on FAs contents in A. truncatum seeds oil, suggesting their significance as critical environmental parameters. Ultimately, we developed a model for potentially ecological suitable regions in China.

CONCLUSION

This study provides a comprehensive understanding of the relationship between metabolome and transcriptome in A. truncatum at various developmental stages of seeds and a new strategy to enhance seed FA content, especially ALA and NA. This is particularly significant in meeting the increasing demands for high-quality edible oil for human consumption. The study offers a scientific basis for A. truncatum's novel utilization as a woody vegetable oil rather than an ornamental plant, potentially expanding its cultivation worldwide.

The EIN3 transcription factor GmEIL1 improves soybean resistance to Phytophthora sojae

Phytophthora root and stem rot of soybean (Glycine max), caused by the oomycete Phytophthora sojae, is an extremely destructive disease worldwide. In this study, we identified GmEIL1, which encodes an ethylene-insensitive3 (EIN3) transcription factor. GmEIL1 was significantly induced following P. sojae infection of soybean plants. Compared to wild-type soybean plants, transgenic soybean plants overexpressing GmEIL1 showed enhanced resistance to P. sojae and GmEIL1-silenced RNA-interference lines showed more severe symptoms when infected with P. sojae. We screened for target genes of GmEIL1 and confirmed that GmEIL1 bound directly to the GmERF113 promoter and regulated GmERF113 expression. Moreover, GmEIL1 positively regulated the expression of the pathogenesis-related gene GmPR1. The GmEIL1-regulated defence response to P. sojae involved both ethylene biosynthesis and the ethylene signalling pathway. These findings suggest that the GmEIL1-GmERF113 module plays an important role in P. sojae resistance via the ethylene signalling pathway.

Potential Regulatory Networks and Heterosis for Flavonoid and Terpenoid Contents in Pak Choi: Metabolomic and Transcriptome Analyses

Pak choi exhibits a diverse color range and serves as a rich source of flavonoids and terpenoids. However, the mechanisms underlying the heterosis and coordinated regulation of these compounds-particularly isorhamnetin-remain unclear. This study involved three hybrid combinations and the detection of 528 metabolites from all combinations, including 26 flavonoids and 88 terpenoids, through untargeted metabolomics. Analysis of differential metabolites indicated that the heterosis for the flavonoid and terpenoid contents was parent-dependent, and positive heterosis was observed for isorhamnetin in the two hybrid combinations (SZQ, 002 and HMG, ZMG). Moreover, there was a high transcription level of flavone 3'-O-methyltransferase, which is involved in isorhamnetin biosynthesis. The third group was considered the ideal hybrid combination for investigating the heterosis of flavonoid and terpenoid contents. Transcriptome analysis identified a total of 12,652 DEGs (TPM > 1) in various groups that were used for comparison, and DEGs encoding enzymes involved in various categories, including "carotenoid bio-synthesis" and "anthocyanin biosynthesis", were enriched in the hybrid combination (SZQ, 002). Moreover, the category of anthocyanin biosynthesis also was enriched in the hybrid combination (HMG, ZMG). The flavonoid pathway demonstrated more differential metabolites than the terpenoid pathway did. The WGCNA demonstrated notable positive correlations between the dark-green modules and many flavonoids and terpenoids. Moreover, there were 23 ERF genes in the co-expression network (r ≥ 0.90 and p < 0.05). Thus, ERF genes may play a significant role in regulating flavonoid and terpenoid biosynthesis. These findings enhance our understanding of the heterosis and coordinated regulation of flavonoid and terpenoid biosynthesis in pak choi, offering insights for genomics-based breeding improvements.

OsACA9, an Autoinhibited Ca2+-ATPase, Synergically Regulates Disease Resistance and Leaf Senescence in Rice

Calcium (Ca2+) is a versatile intracellular second messenger that regulates several signaling pathways involved in growth, development, stress tolerance, and immune response in plants. Autoinhibited Ca2+-ATPases (ACAs) play an important role in the regulation of cellular Ca2+ homeostasis. Here, we systematically analyzed the putative OsACA family members in rice, and according to the phylogenetic tree of OsACAs, OsACA9 was clustered into a separated branch in which its homologous gene in Arabidopsis thaliana was reported to be involved in defense response. When the OsACA9 gene was knocked out by CRISPR/Cas9, significant accumulation of reactive oxygen species (ROS) was detected in the mutant lines. Meanwhile, the OsACA9 knock out lines showed enhanced disease resistance to both rice bacterial blight (BB) and bacterial leaf streak (BLS). In addition, compared to the wild-type (WT), the mutant lines displayed an early leaf senescence phenotype, and the agronomy traits of their plant height, panicle length, and grain yield were significantly decreased. Transcriptome analysis by RNA-Seq showed that the differentially expressed genes (DEGs) between WT and the Osaca9 mutant were mainly enriched in basal immune pathways and antibacterial metabolite synthesis pathways. Among them, multiple genes related to rice disease resistance, receptor-like cytoplasmic kinases (RLCKs) and cell wall-associated kinases (WAKs) genes were upregulated. Our results suggest that the Ca2+-ATPase OsACA9 may trigger oxidative burst in response to various pathogens and synergically regulate disease resistance and leaf senescence in rice.

New Advances in the Study of Regulation of Tomato Flowering-Related Genes Using Biotechnological Approaches

The tomato is a convenient object for studying reproductive processes, which has become a classic. Such complex processes as flowering and fruit setting require an understanding of the fundamental principles of molecular interaction, the structures of genes and proteins, the construction of signaling pathways for transcription regulation, including the synchronous actions of cis-regulatory elements (promoter and enhancer), trans-regulatory elements (transcription factors and regulatory RNAs), and transposable elements and epigenetic regulators (DNA methylation and acetylation, chromatin structure). Here, we discuss the current state of research on tomatoes (2017-2023) devoted to studying the function of genes that regulate flowering and signal regulation systems using genome-editing technologies, RNA interference gene silencing, and gene overexpression, including heterologous expression. Although the central candidate genes for these regulatory components have been identified, a complete picture of their relationship has yet to be formed. Therefore, this review summarizes the latest achievements related to studying the processes of flowering and fruit set. This work attempts to display the gene interaction scheme to better understand the events under consideration.

Recent Advances in Studying the Regulation of Fruit Ripening in Tomato Using Genetic Engineering Approaches

Tomato (Solanum lycopersicum L.) is one of the most commercially essential vegetable crops cultivated worldwide. In addition to the nutritional value, tomato is an excellent model for studying climacteric fruits' ripening processes. Despite this, the available natural pool of genes that allows expanding phenotypic diversity is limited, and the difficulties of crossing using classical selection methods when stacking traits increase proportionally with each additional feature. Modern methods of the genetic engineering of tomatoes have extensive potential applications, such as enhancing the expression of existing gene(s), integrating artificial and heterologous gene(s), pointing changes in target gene sequences while keeping allelic combinations characteristic of successful commercial varieties, and many others. However, it is necessary to understand the fundamental principles of the gene molecular regulation involved in tomato fruit ripening for its successful use in creating new varieties. Although the candidate genes mediate ripening have been identified, a complete picture of their relationship has yet to be formed. This review summarizes the latest (2017-2023) achievements related to studying the ripening processes of tomato fruits. This work attempts to systematize the results of various research articles and display the interaction pattern of genes regulating the process of tomato fruit ripening.

Involvement of Transcription Factors and Regulatory Proteins in the Regulation of Carotenoid Accumulation in Plants and Algae

Carotenoids are essential for photosynthesis and photoprotection in photosynthetic organisms, which are widely used in food coloring, feed additives, nutraceuticals, cosmetics, and pharmaceuticals. Carotenoid biofortification in crop plants or algae has been considered as a sustainable strategy to improve human nutrition and health. However, the regulatory mechanisms of carotenoid accumulation are still not systematic and particularly scarce in algae. This article focuses on the regulatory mechanisms of carotenoid accumulation in plants and algae through regulatory factors (transcription factors and regulatory proteins), demonstrating the complexity of homeostasis regulation of carotenoids, mainly including transcriptional regulation as the primary mechanism, subsequent post-translational regulation, and cross-linking with other metabolic processes. Different organs of plants and different plant/algal species usually have specific regulatory mechanisms for the biosynthesis, storage, and degradation of carotenoids in response to the environmental and developmental signals. In plants and algae, regulators such as MYB, bHLH, MADS, bZIP, AP2/ERF, WRKY, and orange proteins can be involved in the regulation of carotenoid metabolism. And many more regulators, regulatory networks, and mechanisms need to be explored. Our paper will provide a basis for multitarget or multipathway engineering for carotenoid biofortification in plants and algae.

Antioxidants of Non-Enzymatic Nature: Their Function in Higher Plant Cells and the Ways of Boosting Their Biosynthesis

Plants are exposed to a variety of abiotic and biotic stresses leading to increased formation of reactive oxygen species (ROS) in plant cells. ROS are capable of oxidizing proteins, pigments, lipids, nucleic acids, and other cell molecules, disrupting their functional activity. During the process of evolution, numerous antioxidant systems were formed in plants, including antioxidant enzymes and low molecular weight non-enzymatic antioxidants. Antioxidant systems perform neutralization of ROS and therefore prevent oxidative damage of cell components. In the present review, we focus on the biosynthesis of non-enzymatic antioxidants in higher plants cells such as ascorbic acid (vitamin C), glutathione, flavonoids, isoprenoids, carotenoids, tocopherol (vitamin E), ubiquinone, and plastoquinone. Their functioning and their reactivity with respect to individual ROS will be described. This review is also devoted to the modern genetic engineering methods, which are widely used to change the quantitative and qualitative content of the non-enzymatic antioxidants in cultivated plants. These methods allow various plant lines with given properties to be obtained in a rather short time. The most successful approaches for plant transgenesis and plant genome editing for the enhancement of biosynthesis and the content of these antioxidants are discussed.