Isolation and functional validation of the CmLOX08 promoter associated with signalling molecule and abiotic stress responses in oriental melon, Cucumis melo var. makuwa Makino

Enhancing medicinal proteins production in plant bioreactors: A focal review on promoters

The use of plant bioreactors for the production of medicinal proteins has emerged as a promising and cost-effective alternative to traditional microbial and mammalian cell culture systems. This review provides a focused examination of the critical role of promoters in enhancing the production of therapeutic proteins within plant-based platforms. We discuss the latest advancements in promoter discovery, modification, and optimization for the expression of medicinal proteins in plants. The review highlights the challenges and opportunities associated with various types of promoters, including constitutive, tissue-specific, and inducible promoters, and their impact on medicinal protein yield and quality. Case studies are presented to illustrate the successful application of these promoter engineering techniques in plant bioreactors, emphasizing the potential for scalable and sustainable production of pharmaceutical proteins. Additionally, we explore the strategies for improving promoter function. This review is intended to guide researchers and industry professionals in the selection and design of promoters for the enhanced production of medicinal proteins in plant bioreactors.

Molecular Markers for Marker-Assisted Breeding for Biotic and Abiotic Stress in Melon (Cucumis melo L.): A Review

Melon (Cucumis melo L.) is a globally grown crop renowned for its juice and flavor. Despite growth in production, the melon industry faces several challenges owing to a wide range of biotic and abiotic stresses throughout the growth and development of melon. The aim of the review article is to consolidate current knowledge on the genetic mechanism of both biotic and abiotic stress in melon, facilitating the development of robust, disease-resistant melon varieties. A comprehensive literature review was performed, focusing on recent genetic and molecular advancements related to biotic and abiotic stress responses in melons. The review emphasizes the identification and analysis of quantitative trait loci (QTLs), functional genes, and molecular markers in two sections. The initial section provides a comprehensive summary of the QTLs and major and minor functional genes, and the establishment of molecular markers associated with biotic (viral, bacterial, and fungal pathogens, and nematodes) and abiotic stress (cold/chilling, drought, salt, and toxic compounds). The latter section briefly outlines the molecular markers employed to facilitate marker-assisted backcrossing (MABC) and identify cultivars resistant to biotic and abiotic stressors, emphasizing their relevance in strategic marker-assisted melon breeding. These insights could guide the incorporation of specific traits, culminating in developing novel varieties, equipped to withstand diseases and environmental stresses by targeted breeding, that meet both consumer preferences and the needs of melon breeders.

Functional Characterization of CsF3Ha and Its Promoter in Response to Visible Light and Plant Growth Regulators in the Tea Plant

Flavanone 3-hydroxylase (F3H) catalyzes trihydroxyflavanone formation into dihydroflavonols in the anthocyanin biosynthesis pathway, serving as precursors for anthocyanin synthesis. To investigate the CsF3Ha promoter's regulation in the 'Zijuan' tea plant, we cloned the CsF3Ha gene from this plant. It was up-regulated under various visible light conditions (blue, red, and ultraviolet (UV)) and using plant growth regulators (PGRs), including abscisic acid (ABA), gibberellic acid (GA3), salicylic acid (SA), ethephon, and methyl jasmonate (MeJA). The 1691 bp promoter sequence was cloned. The full-length promoter P1 (1691 bp) and its two deletion derivatives, P2 (890 bp) and P3 (467 bp), were fused with the β-glucuronidase (GUS) reporter gene, and were introduced into tobacco via Agrobacterium-mediated transformation. GUS staining, activity analysis, and relative expression showed that visible light and PGRs responded to promoter fragments. The anthocyanin content analysis revealed a significant increase due to visible light and PGRs. These findings suggest that diverse treatments indirectly enhance anthocyanin accumulation in 'Zijuan' tea plant leaves, establishing a foundation for further research on CsF3Ha promoter activity and its regulatory role in anthocyanin accumulation.

Evaluation of cucumber UBL5 promoter as a tool for transgene expression and genome editing in plants

Transgene expression and genome editing can help improve cucumber varieties to better respond to climate change. This study aimed to evaluate the applicability of the CsUBL5 promoter in transgene expression and genome editing in cucumber. The CsUBL5 promoter was cloned and analyzed to identify cis-elements that respond to abiotic signals, hormones, signal molecules, and nutrient treatments. 5' deletion constructs of the promoter were tested for their ability to drive GUS reporter expression in cucumber cotyledons, Arabidopsis seedlings, and tobacco leaves, and their response to various treatments including SA, light, drought, IAA, and GA was determined. The results showed that the CsUBL5 promoter effectively drove transgene expression in these plants, and their expressions under treatments were consistent with the predicted cis-elements, with some exceptions. Furthermore, the pCsUBL5-749 deletion construct can improve genome editing efficiency in cucumber when driving Cas9 expression. The editing efficiency of two sgRNAs targeting the ATG6 gene in cucumber was up to 4.6-fold higher using pCsUBL5-749 compared to a rice UBI promoter, although the effects of changing promoter on the editing efficiency is sgRNA specific. These findings highlight the potential utility of the CsUBL5 promoter for improving cucumber varieties through genetic engineering and genome editing. It also demonstrates the importance of modulating Cas9 expression to increase genome editing efficiency in cucumbers.

A New Function of MbIAA19 Identified to Modulate Malus Plants Dwarfing Growth

The primary determinants of apple (Malus) tree architecture include plant height and internode length, which are the significant criteria for evaluating apple dwarf rootstocks. Plant height and internode length are predominantly governed by phytohormones. In this study, we aimed to assess the mechanisms underlying dwarfism in a mutant of Malus baccata. M. baccata dwarf mutant (Dwf) was previously obtained through natural mutation. It has considerably reduced plant height and internode length. A comparative transcriptome analysis of wild-type (WT) and Dwf mutant was performed to identify and annotate the differentially expressed genes responsible for the Dwf phenotype using RNA-seq and GO and KEGG pathway enrichment analyses. Multiple DEGs involved in hormone signaling pathways, particularly auxin signaling pathways, were identified. Moreover, the levels of endogenous indole-3-acetic acid (IAA) were lower in Dwf mutant than in WT. The Aux/IAA transcription factor gene MbIAA19 was downregulated in Dwf mutant due to a single nucleotide sequence change in its promoter. Genetic transformation assay demonstrated strong association between MbIAA19 and the dwarf phenotype. RNAi-IAA19 lines clearly exhibited reduced plant height, internode length, and endogenous IAA levels. Our study revealed that MbIAA19 plays a role in the regulation of dwarfism and endogenous IAA levels in M. baccata.

Cloning of the promoter of rice brown planthopper feeding-inducible gene OsTPS31 and identification of related cis-regulatory elements

BACKGROUND

Brown planthopper (BPH; Nilaparvata lugens) is one of the most serious pests of rice in the world. Insect-resistant genetic engineering is a very effective technology to control BPH. The promoters and cis-regulatory elements inducible by plant-feeding insects are critical for genetic engineering of insect-resistant crops.

RESULTS

In this study, we cloned a promoter Ptps31 and a 7 bp cis-regulatory sequence that up-regulated downstream genes induced by BPH feeding. The promoter of OsTPS31 (Ptps31) unresponsive to physical damage but responsive to BPH feeding was cloned and functionally verified. The results showed that expression of the OsBPH14 gene driven by the promoter region from -510 to -246 bp in rice could significantly improve the resistance to BPH. The promoter region from -376 to -370 bp (TAGTGTC) was identified as a cis-regulatory sequence related to BPH feeding induction of downstream gene expression.

CONCLUSION

The findings provide a new promoter and a new cis-regulatory sequence tool for the research on and application of rice BPH resistance genes, as well as a new perspective for functional analysis of the OsTPS31 gene. © 2023 Society of Chemical Industry.

Functional Characterization of TkSRPP Promoter in Response to Hormones and Wounding Stress in Transgenic Tobacco

Taraxacum kok-saghyz is a model species for studying natural rubber biosynthesis because its root can produce high-quality rubber. Small rubber particle protein (SRPP), a stress-related gene to multiple stress responses, involves in natural rubber biosynthesis. To investigate the transcriptional regulation of the TkSRPP promoter, the full-length promoter PR0 (2188 bp) and its four deletion derivatives, PR1 (1592 bp), PR2 (1274 bp), PR3 (934 bp), and PR4 (450 bp), were fused to β-glucuronidase (GUS) reporter gene and transformed into tobacco. The GUS tissue staining showed that the five promoters distinctly regulated GUS expression utilizing transient transformation of tobacco. The GUS activity driven by a PR0 promoter was detected in transgenic tobacco leaves, stem and roots, suggesting that the TkSRPP promoter was not tissue-specific. Deletion analyses in transgenic tobacco have demonstrated that the PR3 from -934 bp to -450 bp core region responded strongly to the hormones, methyl jasmonate (MeJA), abscisic acid (ABA), and salicylic acid (SA), and also to injury induction. The TkSRPP gene was highly expressed under hormones and wound-induced conditions. This study reveals the regulation pattern of the SRPP promoter, and provides valuable information for studying natural rubber biosynthesis under hormones and wounding stress.

Structural and functional analysis of stress-inducible genes and their promoters selected from young oil palm (Elaeis guineensis) under salt stress

Background

Soil salinity is a problem in more than 100 countries across all continents. It is one of the abiotic stress that threatens agriculture the most, negatively affecting crops and reducing productivity. Transcriptomics is a technology applied to characterize the transcriptome in a cell, tissue, or organism at a given time via RNA-Seq, also known as full-transcriptome shotgun sequencing. This technology allows the identification of most genes expressed at a particular stage, and different isoforms are separated and transcript expression levels measured. Once determined by this technology, the expression profile of a gene must undergo validation by another, such as quantitative real-time PCR (qRT-PCR). This study aimed to select, annotate, and validate stress-inducible genes—and their promoters—differentially expressed in the leaves of oil palm (Elaeis guineensis) plants under saline stress.

Results

The transcriptome analysis led to the selection of 14 genes that underwent structural and functional annotation, besides having their expression validated using the qRT-PCR technique. When compared, the RNA-Seq and qRT-PCR profiles of those genes resulted in some inconsistencies. The structural and functional annotation analysis of proteins coded by the selected genes showed that some of them are orthologs of genes reported as conferring resistance to salinity in other species. There were those coding for proteins related to the transport of salt into and out of cells, transcriptional regulatory activity, and opening and closing of stomata. The annotation analysis performed on the promoter sequence revealed 22 distinct types of cis-acting elements, and 14 of them are known to be involved in abiotic stress.

Conclusion

This study has helped validate the process of an accurate selection of genes responsive to salt stress with a specific and predefined expression profile and their promoter sequence. Its results also can be used in molecular-genetics-assisted breeding programs. In addition, using the identified genes is a window of opportunity for strategies trying to relieve the damages arising from the salt stress in many glycophyte crops with economic importance.

Transcription Factor CmNAC34 Regulated CmLCYB-Mediated β-Carotene Accumulation during Oriental Melon Fruit Ripening

Ripened oriental melon (Cucumis melo) with orange-colored flesh is rich in β-carotene. Lycopene β-cyclase (LCYB) is the synthetic enzyme that directly controls the massive accumulation of β-carotene. However, the regulatory mechanism underlying the CmLCYB-mediated β-carotene accumulation in oriental melon is fairly unknown. Here, we screened and identified a transcription factor, CmNAC34, by combining bioinformatics analysis and yeast one-hybrid screen with CmLCYB promoter. CmNAC34 was located in the nucleus and acted as a transcriptional activator. The expression profile of CmNAC34 was consistent with that of CmLCYB during the fruit ripening. Additionally, the transient overexpression of CmNAC34 in oriental melon fruit promoted the expression of CmLCYB and enhanced β-carotene concentration, while transient silence of CmNAC34 in fruit was an opposite trend, which indicated CmNAC34 could modulate CmLCYB-mediated β-carotene biosynthesis in oriental melon. Finally, the yeast one-hybrid (Y1H), electrophoretic mobility shift assay (EMSA), β-glucuronidase (GUS) analysis assay, and luciferase reporter (LUC) assay indicated that CmNAC34 could bind to the promoter of CmLCYB and positively regulated the CmLCYB transcription level. These findings suggested that CmNAC34 acted as an activator to regulate β-carotene accumulation by directly binding the promoter of CmLCYB, which provides new insight into the regulatory mechanism of carotenoid metabolism during the development and ripening of oriental melon.

Analysis of Thioredoxins and Glutaredoxins in Soybean: Evidence of Translational Regulation under Water Restriction

Soybean (Glycine max (L.) Merr.) establishes symbiosis with rhizobacteria, developing the symbiotic nodule, where the biological nitrogen fixation (BNF) occurs. The redox control is key for guaranteeing the establishment and correct function of the BNF process. Plants have many antioxidative systems involved in ROS homeostasis and signaling, among them a network of thio- and glutaredoxins. Our group is particularly interested in studying the differential response of nodulated soybean plants to water-deficit stress. To shed light on this phenomenon, we set up an RNA-seq experiment (for total and polysome-associated mRNAs) with soybean roots comprising combined treatments including the hydric and the nodulation condition. Moreover, we performed the initial identification and description of the complete repertoire of thioredoxins (Trx) and glutaredoxins (Grx) in soybean. We found that water deficit altered the expression of a greater number of differentially expressed genes (DEGs) than the condition of plant nodulation. Among them, we identified 12 thioredoxin (Trx) and 12 glutaredoxin (Grx) DEGs, which represented a significant fraction of the detected GmTrx and GmGrx in our RNA-seq data. Moreover, we identified an enriched network in which a GmTrx and a GmGrx interacted with each other and associated through several types of interactions with nitrogen metabolism enzymes.

Running title: ABA pathway meets CBF pathway at CmADC

Low temperatures severely restrict melon-seedling growth. However, the mechanisms by which melon adapts to cold stress are poorly understood. Arginine decarboxylase (ADC), a key synthetase, catalyzes putrescine biosynthesis in plants. In this study, we found that CmADC functions as a positive regulator of melon-seedling cold tolerance. In addition, two transcription factors, abscisic acid-responsive element (ABRE)-binding factor 1 (CmABF1) and C-repeat binding factor 4 (CmCBF4), directly target CmADC to trigger its expression. Consistently, virus-induced gene silencing (VIGS) of CmABF1 or CmCBF4 downregulated CmADC abundance, decreased putrescine accumulation and reduced cold tolerance. Furthermore, some other CBF and ABF members, at least in part, have functional redundancy and complementarity with CmABF1 and CmCBF4. Overall, our work reveals that the ABA, CBF and polyamine pathways may form a regulatory network to co-participate in plant cold stress.

Effects of exogenous phytohormones on chlorogenic acid accumulation and pathway-associated gene expressions in sweetpotato stem tips

Sweetpotato (Ipomoea batatas [L.] Lam.) stem tips, which contain high concentrations of chlorogenic acid (CGA), are useful as a physiologically functional food to protect against some serious diseases. According to previous studies, exogenous application of phytohormones may be an effective agrotechnical measure to control CGA biosynthesis through the transcriptional regulation of pathway gene expressions. To understand the mechanism of CGA biosynthesis in sweetpotato, we investigated the effects of exogenous phytohormones on CGA metabolism in stem tips of sweetpotato. A significantly elevated CGA content was observed in salicylic acid (SA)-treated sweetpotato stem tips at 72 h, as well as in those subjected to abscisic acid (ABA) or gibberellic acid (GA) treatments. Dynamic expression change of seven enzyme genes involved in sweetpotato CGA biosynthesis were analyzed to determine correlations between transcript levels and CGA accumulation. As revealed by the differential expression of these genes under distinct phytohormone treatments, the regulation of specific pathway genes is a critical determinant of the accumulation of CGA in sweetpotato stem tips. We also found that several hormone-responsive sites, such as those for ABA, GA, SA, and jasmonic acid (JA), were present in the promoter regions of sweetpotato CGA biosynthestic pathway genes. Collectively, phytohormones can regulate the transcription of CGA synthesis-related genes and ultimately affect CGA accumulation in sweetpotato stem tips, whereas the regulatory differences are mirrored by cis-acting elements in the corresponding pathway gene promoters.

Drought-induced ABA, H2O2 and JA positively regulate CmCAD genes and lignin synthesis in melon stems

BACKGROUND

Cinnamyl alcohol dehydrogenase (CAD) is an important enzyme functions at the last step in lignin monomer synthesis pathway. Our previous work found that drought induced the expressions of CmCAD genes and promoted lignin biosynthesis in melon stems.

RESULTS

Here we studied the effects of abscisic acid (ABA), hydrogen peroxide (H2O2) and jasmonic acid (JA) to CmCADs under drought stress. Results discovered that drought-induced ABA, H2O2 and MeJA were prevented efficiently from increasing in melon stems pretreated with fluridone (Flu, ABA inhibitor), imidazole (Imi, H2O2 scavenger) and ibuprofen (Ibu, JA inhibitor). ABA and H2O2 are involved in the positive regulations to CmCAD1, 2, 3, and 5, and JA is involved in the positive regulations to CmCAD2, 3, and 5. According to the expression profiles of lignin biosynthesis genes, ABA, H2O2 and MeJA all showed positive regulations to CmPAL2-like, CmPOD1-like, CmPOD2-like and CmLAC4-like. In addition, positive regulations were also observed with ABA to CmPAL1-like, CmC4H and CmCOMT, with H2O2 to CmPAL1-like, CmC4H, CmCCR and CmLAC17-like, and with JA to CmCCR, CmCOMT, CmLAC11-like and CmLAC17-like. As expected, the signal molecules positively regulated CAD activity and lignin biosynthesis under drought stress. Promoter::GUS assays not only further confirmed the regulations of the signal molecules to CmCAD1~3, but also revealed the important role of CmCAD3 in lignin synthesis due to the strongest staining of CmCAD3 promoter::GUS.

CONCLUSIONS

CmCADs but CmCAD4 are positively regulated by ABA, H2O2 and JA under drought stress and participate in lignin synthesis.

The Molecular and Functional Characterization of the Durum Wheat Lipoxygenase TdLOX2 Suggests Its Role in Hyperosmotic Stress Response

In plants, lipoxygenases (LOXs) are involved in various processes, such as growth, development, and response to stress cues. In the present study, the expression pattern of six durum wheat LOX-encoding genes (TdLpx-B1.1, TdLpx-B1.2, TdLpx-A2, TdLpx-B2, TdLpx-A3 and TdLpx-B3) under hyperosmotic stress was investigated. With osmotic (0.42 M mannitol) and salt (0.21 M NaCl) stress imposed at the early stages of seedling growth, a strong induction of the TdLpx-A2 gene expression in the shoots paralleled an equally strong increase in the LOX activity. Enhanced levels of malondialdehyde (MDA) and increased rates of superoxide anion generation were also observed as a result of the stress imposition. Sequence analysis of the TdLOX2 encoded by the TdLpx-A2 gene revealed that it belonged to the type-1 9-LOX group. When overexpressed in E. coli, TdLOX2 exhibited normal enzyme activity, high sensitivity to specific LOX inhibitors, with 76% and 99% inhibition by salicylhydroxamic and propyl gallate, respectively, and a preference for linoleic acid as substrate, which was converted exclusively to its corresponding 13-hydroperoxide. This unexpected positional specificity could be related to the unusual TV/K motif that in TdLOX2 replaces the canonical TV/R motif of 9-LOXs. Treatment of seedlings with propyl gallate strongly suppressed the increase in LOX activity induced by the hyperosmotic stress; the MDA accumulation was also reduced but less markedly, whereas the rate of superoxide anion generation was even more increased. Overall, our findings suggest that the up-regulation of the TdLpx-A2 gene is a component of the durum wheat response to hyperosmotic stress and that TdLOX2 may act by counteracting the excessive generation of harmful reactive oxygen species responsible for the oxidative damages that occur in plants under stress.

The RhHB1/RhLOX4 module affects the dehydration tolerance of rose flowers (Rosa hybrida) by fine-tuning jasmonic acid levels

Phytohormones are key factors in plant responsiveness to abiotic and biotic stresses, and maintaining hormone homeostasis is critically important during stress responses. Cut rose (Rosa hybrida) flowers experience dehydration stress during postharvest handling, and jasmonic acid (JA) levels change as a result of this stress. However, how JA is involved in dehydration tolerance remains unclear. We investigated the functions of the JA- and dehydration-induced RhHB1 gene, which encodes a homeodomain-leucine zipper I γ-clade transcription factor, in rose flowers. Silencing RhHB1 decreased petal dehydration tolerance and resulted in a persistent increase in JA-Ile content and reduced dehydration tolerance. An elevated JA-Ile level had a detrimental effect on rose petal dehydration tolerance. RhHB1 was shown to lower the transient induction of JA-Ile accumulation in response to dehydration. In addition to transcriptomic data, we obtained evidence that RhHB1 suppresses the expression of the lipoxygenase 4 (RhLOX4) gene by directly binding to its promoter both in vivo and in vitro. We propose that increased JA-Ile levels weaken the capacity for osmotic adjustment in petal cells, resulting in reduced dehydration tolerance. In conclusion, a JA feedback loop mediated by an RhHB1/RhLOX4 regulatory module provides dehydration tolerance by fine-tuning bioactive JA levels in dehydrated flowers.