Brassinosteroid Biosynthesis Research Articles

A mutation in CsDWF7 gene encoding a delta7 sterol C-5(6) desaturase leads to the phenotype of super compact in cucumber (Cucumis sativus L.).

A novel super compact mutant, scp-3, was identified using map-based cloning in cucumber. The CsDWF7 gene encoding a delta7 sterol C-5(6) desaturase was the candidate gene of scp-3. Mining dwarf genes is important in understanding stem growth in crops. However, only a small number of dwarf genes have been cloned or characterized. Here, we characterized a cucumber (Cucumis sativus L.) dwarf mutant, super compact 3 (scp-3), which displays shortened internodes and dark green leaves with a wrinkled appearance. The photosynthetic rate of scp-3 is significantly lower than that of the wild type. The dwarf phenotype of scp-3 mutant can be partially rescued by the exogenous brassinolide (BL) application, and the endogenous brassinosteroids (BRs) levels in the scp-3 mutant were significantly lower compared to the wild type. Microscopic examination revealed that the reduced internode length in scp-3 resulted from a decrease in cell size. Genetic analysis showed that the dwarf phenotype of scp-3 was controlled by a single recessive gene. Combined with bulked segregant analysis and map-based cloning strategy, we delimited scp-3 locus into an 82.5kb region harboring five putative genes, but only one non-synonymous mutation (A to T) was discovered between the mutant and its wild type in this region. This mutation occurred within the second exon of the CsGy4G017510 gene, leading to an amino acid alteration from Leu156 to His156. This gene encodes the CsDWF7 protein, an analog of the Arabidopsis DWF7 protein, which is known to be involved in the biosynthesis of BRs. The CsDWF7 protein was targeted to the cell membrane. In comparison to the wild type, scp-3 exhibited reduced CsDWF7 expression in different tissues. These findings imply that CsDWF7 is essential for both BR biosynthesis as well as growth and development of cucumber plants.

Genome-wide identification and expression profiles of the Phytophthora infestans responsive CYPome (cytochrome P450 complement) in Solanum tuberosum.

Cytochrome P450s represent one of the largest protein families across all domains of life. In plants, biotic stress can regulate the expression of some P450 genes. However, the CYPome (cytochrome P450 complement) in Solanum tuberosum and its response to Phytophthora infestans infection remains unrevealed. In this study, 488 P450 genes were identified from potato genome, which can be divided into 41 families and 57 subfamilies. Responding to the infection of P. infestans, 375 potato P450 genes were expressed in late blight resistant or susceptible cultivars. A total of 14 P450 genes were identified as resistant related candidates, and 81 P450 genes were identified as late blight responsive candidates. Several phytohormone biosynthesis, brassinosteroid biosynthesis, and phenylpropanoid biosynthesis involved P450 genes were differentially expressed during the potato-pathogen interactions. This study firstly reported the CYPome in S. tuberosum, and characterized the expression patterns of these P450 genes during the infection of P. infestans.

Melatonin enhances cadmium tolerance in rice via long non-coding RNA-mediated modulation of cell wall and photosynthesis

In plants, melatonin (MLT) is a versatile signaling molecule involved in promoting plant development and mitigating the damage caused by heavy metal exposure. Long non-coding RNAs (lncRNAs) are essential components in the plant’s response to various abiotic stress, functioning within the gene regulatory network. Here, a hydroponic experiment was performed to explore the involvement of lncRNAs in MLT-mediated amelioration of cadmium (Cd) toxicity in rice plants. The results demonstrated that applying 250 mg L–1 MLT in a solution containing 10 μM Cd leads to an effective reduction of 30.0% in shoot Cd concentration. Remarkably, the treatment resulted in a 21.2% improvement in potassium and calcium uptake, a 164.5% enhancement in net photosynthetic rate, and a 33.2% decrease in malondialdehyde accumulation, resulting increases in plant height, root length, and biomass accumulation. Moreover, a transcriptome analysis revealed 2510 differentially expressed transcripts, including the Cd transporters (–3.82-fold downregulated) and the Cd tolerance-associated genes (1.24-fold upregulated). Notably, regulatory network prediction uncovered 6 differentially expressed lncRNAs that act as competitive endogenous RNA or in RNA complex interactions. These key lncRNAs regulate the expression of target genes that are involved in pectin and cellulose metabolism, scavenging of reactive oxygen species, salicylic acid-mediated defense response, and biosynthesis of brassinosteroids, which ultimately modify the cell wall for Cd adsorption, safeguard photosynthesis, and control hormone signaling to reduce Cd toxicity. Our results unveiled a crucial lncRNA-mediated mechanism underlying MLT’s role in Cd detoxification in rice plants, providing potential applications in agricultural practices and environmental remediation.

Biological control of potato common scab and growth promotion of potato by Bacillus velezensis Y6.

Potato common scab, caused mainly by Streptomyces scabies, causes surface necrosis and reduces the economic value of potato tubers, but effective chemical control is still lacking. In this study, an attempt was made to control potato common scab by inoculating potatoes with Bacillus velezensis (B. velezensis) and to further investigate the mechanism of biological control. The results showed that B. velezensis Y6 could reduce the disease severity of potato common scab from 49.92 ± 25.74% [inoculated with Streptomyces scabies (S. scabies) only] to 5.56 ± 1.89% (inoculated with S. scabies and Y6 on the same day) and increase the potato yield by 37.32% compared with the control under pot experiment in this study. Moreover, in the field trial, it was found that Y6 could also significantly reduce disease severity from 13.20 ± 1.00% to 4.00 ± 0.70% and increase the potato yield from 2.07 ± 0.10 ton/mu to 2.87 ± 0.28 ton/mu (p < 0.01; Tukey's test). Furthermore, RNA-seq analysis indicated that 256 potato genes were upregulated and 183 potato genes were downregulated in response to B. velezensis Y6 inoculation. In addition, strain Y6 was found to induce the expression of plant growth-related genes in potato, including cell wall organization, biogenesis, brassinosteroid biosynthesis, and plant hormone transduction genes, by 1.01-4.29 times. As well as up-regulate hydroquinone metabolism-related genes and several transcription factors (bHLH, MYB, and NAC) by 1.13-4.21 times. In summary, our study will help to understand the molecular mechanism of biological control of potato common scab and improve potato yield.

Brassinosteroid Signaling Pathways: Insights into Plant Responses under Abiotic Stress.

With the growing global population, abiotic factors have emerged as a formidable threat to agricultural food production. If left unaddressed, these stress factors might reduce food yields by up to 25% by 2050. Plants utilize natural mechanisms, such as reactive oxygen species scavenging, to mitigate the adverse impacts of abiotic stressors. Diverse plants exhibit unique adaptations to abiotic stresses, which are regulated by phytohormones at various levels. Brassinosteroids (BRs) play a crucial role in controlling essential physiological processes in plants, including seed germination, xylem differentiation, and reproduction. The BR cascade serves as the mechanism through which plants respond to environmental stimuli, including drought and extreme temperatures. Despite two decades of research, the complex signaling of BRs under different stress conditions is still being elucidated. Manipulating BR signaling, biosynthesis, or perception holds promise for enhancing crop resilience. This review explores the role of BRs in signaling cascades and summarizes their substantial contribution to plants' ability to withstand abiotic stresses.

The overexpression of SlBRI1 driven by Atrd29A promoter-transgenic plants improves the chilling stress tolerance of tomato.

Overexpression of SlBRI1 driven by the Atrd29A promoter could increase the cold resistance of tomato plants during chilling stress but did not improve the expression of SlBRI1 and plant growth under normal conditions. Low temperature is the main limiting factor severely affecting tomato plant development, growth, and fruit quality in winter and spring. Brassinosteroids (BRs) and key BR signaling genes positively regulate tomato plant development and response to chilling stress. Brassinosteroid-insensitive 1 (BRI1) is a major BR receptor that initiates BR signaling. Our results showed that overexpression of SlBRI1 driven by the Atrd29A promoter in transgenic plants did not increase the expression of SlBRI1 under normal conditions but rapidly induced the expression of SlBRI1 during chilling stress. The degree of wilting was lower in Atrd29A promoter-transgenic plants than in wild-type (WT) plants after chilling stress. Atrd29A promoter-transgenic plants exhibited low relative electrolyte leakage and reactive oxygen species (ROS) accumulation under chilling stress. Transgenic plants showed higher photosynthetic ability and antioxidant enzyme activity than WT plants under chilling stress. The BR content and expression levels of key genes involved in BR biosynthesis in Atrd29A-promoter transgenic plants were significantly lower than those in WT plants during chilling stress. The abscisic acid (ABA) content and expression levels of key ABA biosynthesis genes in the Atrd29A promoter-transgenic plants were significantly higher than those in the WT plants during chilling stress. In addition, Atrd29A promoter-transgenic plants positively enhanced the expression levels of ICE-CBF-COR cold-responsive pathway genes. Therefore, the overexpression of SlBRI1 driven by the Atrd29A promoter in transgenic plants can be a valuable tool for reducing chilling stress.

Protective mechanisms of neral as a plant-derived safener against fenoxaprop-p-ethyl injury in rice.

The use of herbicide safeners effectively minimises crop damage while maintaining the full efficacy of herbicides. The present study aimed to assess the potential protective effects of neral (NR) as a safener, in order to mitigate injury caused by fenoxaprop-p-ethyl (FE) on rice. The alleviating effect of NR was similar to that of the safener isoxadifen-ethyl (IE). The root elongation of rice was significantly promoted under the FE + NR and FE + IE treatments, as compared to the FE treatment. The transcriptome analysis further suggested that the effects of NR treatment on plant metabolic pathways differed from those of IE treatment. In total, 895 and 47 up-differentially expressed genes induced by NR (NR-inducible genes) and IE (IE-inducible genes) were identified. NR-inducible genes were mainly enriched in phytohormone synthesis and signalling response, including 'response to brassinosteroid', 'response to jasmonic acid', 'response to ethylene', 'brassinosteroid metabolic process', 'brassinosteroid biosynthesis' and 'plant hormone signal transduction'. In contrast, IE-inducible genes were predominantly enriched in glutathione metabolism. The activity of glutathione S-transferase was found to be increased after IE treatment, whereas no significant increase was observed following NR treatment. Moreover, several transcription factor genes, such as those encoding AP2/ERF-ERF and (basic helix-loop-helix) bHLH were found to be significantly induced by NR treatment. This is the first report of the utilisation of NR as an herbicide safener. The results of this study suggest the toxicity of FE to rice is mitigated by NR through a distinct mechanism compared to IE. © 2023 Society of Chemical Industry.

Comparative proteomic analysis of the moderately resistant and susceptible peanut cultivars during infestation by Cylindrocladium parasiticum

Cylindrocladium parasiticum Crous, Wingfield & Alfenas, the causal agent of Cylindrocladium black rot of peanut, has led to economic losses in China. However, the response of peanut plant to C. parasiticum is poorly understood. Here, two contrasting peanut cultivars, T09 (C. parasiticum-moderately resistant) and P562 (C. parasiticum-susceptible) were used for comparative analysis of protein profiles in root segment of plant tissues in responses to C. parasiticum infection. Proteomic profiling identified 1647 and 391 differentially accumulated proteins (DAPs) in P562 and T09 relative to uninoculated control, respectively. A total of 350 and 1095 DAPs were identified between P562 and T09 after 9 day(s) post infection (dpi), respectively. Functional categorization showed that C. parasiticum-responsive proteins were mainly involved in catalytic activity and binding functions. KEGG pathway analysis indicated both moderately resistant and susceptible peanut cultivars can regulate gene expression in the phenylpropanoid pathway, terpenoid backbone biosynthesis, SA, and JA pathways to induce defensive genes and protein expression which enhances plant defence or susceptibility capacity. However, MAPK signal pathway was more pronounced in moderately resistant peanut cultivar T09. We also observed an increase of CYP73A100 involved in phenylpropanoid and flavonoid biosynthesis pathways in susceptible peanut ecotype P562, while decrease in moderately resistant interaction. Additionally, there was a marked activation of brassinosteroid biosynthesis in T09, which indicated a possible involvement of activation of plant immune response in moderately resistant responses of peanut to C. parasiticum. This study provides some insights into molecular networks involved in cellular and physiological responses to C. parasiticum in peanut.

Integrating Full-Length and Second-Generation Transcriptomics to Reveal Differentially Expressed Genes Associated with the Development of Corydalis yanhusuo Tuber.

Corydalis yanhusuo is a medicinal herb in China that has been widely used to treat various kinds of pain. The tuber is the main organ of C. yanhusuo used for medicinal purposes, but changes in related genes during the development of the tuber have rarely been reported. To identify the differentially expressed genes during tuber development, C. yanhusuo full-length transcriptomic sequencing was performed using single-molecule real-time technology, and tubers at three development stages were selected for comparative transcriptome analysis. A total of 90,496 full-length non-chimeric transcripts were obtained, and 19,341 transcripts were annotated in at least one public database. A total of 9221 differentially expressed genes were identified during the swelling process of C. yanhusuo tuber. A Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis revealed that differentially expressed genes associated with a "starch and sucrose metabolism pathway", "phenylpropanoid biosynthesis pathway", "isoquinoline alkaloid biosynthesis pathway", "zeatin biosynthesis pathway", and "brassinosteroid biosynthesis pathway" were predominantly enriched. In addition, the genes involved in cell wall metabolism were potentially associated with tuber swelling. These processes regulated and were involved in C. yanhusuo tuber development. The results provide a foundation for further research on tuber formation in medicinal plants.

Bioprospecting of phytohormone biosynthetic pathways in the microalgal realm

Microalgae are considered sustainable factories for high added value metabolites, with growing applications in industrial or biomedical biotechnology. Carotenoids and polyunsatured fatty acids (PUFAs) are the main targets. Vitamins or polyphenols are also of interest. Metabolites such as phytohormones have not been contemplated so far in microalgae, especially due to a notable gap of knowledge. This study aimed to explore and compare the biosynthetic pathways of phytohormones along the diverse microalgal taxa, discussing the results together with data available on the qualitative and quantitative assessment of phytohormones in microalgae. A multistep in silico analysis was carried out using a selection of core enzymes from the pathways described in the flowering plant species Arabidopsis thaliana. Results showed that the enzymatic machinery for phytohormone biosynthesis known in plants is generally present in microalgae. Phylogenetic analysis inferred conserved biosynthetic routes in microalgal divisions for abscisic acid, auxins, cytokinins, ethylene and jasmonates. Endosymbiotic events generating phyla such as Ochrophyta, Cryptophyta, Haptophyta or Dinophyta likely determined divergences in the biosynthesis of auxins, gibberellins, and brassinosteroids. Microalgae can be a resource for PHs production with human health benefits, together with carotenoids, polyphenols or vitamins.

BBX21 Integrates Brassinosteroid Biosynthesis andSignaling inthe Inhibition ofHypocotyl Growth under Shade.

B-Box-containing zinc finger transcription factors (BBX) are involved in light-mediated growth, affecting processes such as hypocotyl elongation in Arabidopsis thaliana. However, the molecular and hormonal framework that regulates plant growth through BBX proteins is incomplete. Here, we demonstrate that BBX21 inhibits the hypocotyl elongation through the brassinosteroid (BR) pathway. BBX21 reduces the sensitivity to 24-epiBL, a synthetic active BR, principally at very low concentrations in simulated shade. The biosynthesis profile of BRs showed that two active BR-brassinolide and 28-homobrassinolide-and 8 of 11 intermediates can be repressed by BBX21 under white light (WL) or simulated shade. Furthermore, BBX21 represses the expression of CYTOCHROME P450 90B1 (DWF4/CYP90B1), BRASSINOSTEROID-6-OXIDASE 1 (BR6OX1, CYP85A1) and BR6OX2 (CYP85A2) genes involved in the BR biosynthesis in WL while specifically promoting DWF4 and PHYB ACTIVATION TAGGED SUPPRESSOR 1 (CYP2B1/BAS1) expression in WL supplemented with far-red (WL + FR), a treatment that simulates shade. In addition, BBX21 represses BR signaling genes, such as PACLOBUTRAZOL RESISTANCE1 (PRE1), PRE3 and ARABIDOPSIS MYB-LIKE 2 (MYBL2), and auxin-related and expansin genes, such as INDOLE-3-ACETIC ACID INDUCIBLE 1 (IAA1), IAA4 and EXPANSIN 11 in short-term shade. By a genetic approach, we found that BBX21 acts genetically upstream of BRASSINAZOLE-RESISTANT 1 (BZR1) for the promotion of DWF4 and BAS1 gene expression in shade. We propose that BBX21 integrates the BR homeostasis and shade-light signaling, allowing the fine-tuning of hypocotyl elongation in Arabidopsis.

Transcriptomic and Metabolomic Analyses of Seedlings of Two Grape Cultivars with Distinct Tolerance Responses to Flooding and Post-Flooding Stress Conditions

Grapes, an important and widespread fruit crop providing multiple products, face increasing flooding risks due to intense and frequent extreme rainfall. It is thus imperative to fully understand the flood-tolerance mechanisms of grapevines. Here, RNA-seq and LC-MS/MS technologies were used to analyze the transcriptome and metabolome changes in the roots of SO4 (tolerant to flooding) and Kyoho (sensitive to flooding) grapes under flooding and post-flooding conditions. The results showed that the abundance of many metabolites in the phenylpropanoids and polyketides, organic acids and their derivatives, and organic oxygen compounds superclasses changed in different patterns between the Kyoho and SO4 grapes under flooding and post-flooding conditions. Jasmonic acid and the ascorbic acid–glutathione cycle played a pivotal role in coping with both hypoxia stress and reoxygenation stress incurred during flooding and post-flooding treatments in the SO4 cultivar. Under flooding stress, the regulatory mechanistic shift from aerobic respiration to anaerobic fermentation under hypoxia is partly missing in the Kyoho cultivar. In the post-flooding stage, many genes related to ethylene, gibberellins, cytokinins, and brassinosteroids biosynthesis and brassinosteroids-responsive genes were significantly downregulated in the Kyoho cultivar, adversely affecting growth recovery; however, their expression was not reduced in the SO4 cultivar. These findings enhance our understanding of the flooding-tolerance mechanisms in grapes.

MtTGA1 Transcription Factor Enhances Salt Tolerance through Hormonal Regulation and Antioxidant Enzyme Activity in Medicago truncatula

The TGACG motif-binding factor1 (TGA1) transcription factor, in which belongs to the bZIP transcription factor family and has vast application potential in plant growth and development. Here, we cloned the gene of the MtTGA1 transcription factor from Medicago truncatula. The MtTGA1 promoter region contains a diverse range of photoregulatory and hormonal regulatory elements. The expression profile of MtTGA1 indicated its highest expression in the root. Additionally, the expression level of MtTGA1 was significantly upregulated after SA and BR treatments and showed a downward trend after GA and ABA treatments. To explore the potential function of MtTGA1, we treated the transgenic plants with salt treatment for 15 days, and the results showed that transgenic plants demonstrated significantly longer root lengths and heightened activities of antioxidant enzymes such as ascorbic acid catalase (APX), peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) in their roots and leaves. The levels of endogenous hormones, including ABA and BR were improved in transgenic plants, with a marked change in the morphology of their leaf cells. Transcriptome analysis identified a total of 193 differentially expressed genes, which were significantly enriched in the pathways of “Brassinosteroid biosynthesis”, “Ascorbate and aldarate metabolism”, and “Plant hormone signal transduction”. Furthermore, MtTGA1 was found to interact with the SPX domain-containing protein 1 (SPX1) in Medicago truncatula. In conclusion, these results are beneficial for further studies about the plant growth and development regulatory network mediated by the TGA1 transcription factor family.

Combined analysis of microRNA and mRNA profiles provides insights into the pathogenic resistant mechanisms of the lotus rhizome rot.

Lotus rhizome rot caused by Fusarium oxysporum is a common vascular fungal disease in plants that significantly impacts the yield. However, only a few studies have studied the mechanism of Nelumbo nucifera responding to lotus rhizome rot. Here, we investigated the pathogenic genes and miRNAs in lotus rhizome rot to uncover the pathogenic resistant mechanisms by transcriptome and small RNA sequencing of lotus roots after inoculation with Fusarium oxysporum. GO and KEGG functional enrichment analysis showed that differential miRNAs were mostly enriched in starch and sucrose metabolism, biosynthesis of secondary metabolites, glutathione metabolism, brassinosteroid biosynthesis and flavonoid biosynthesis pathways. Twenty-seven upregulated miRNAs, 19 downregulated miRNAs and their target genes were identified. Correlation analysis found that miRNAs negatively regulate target genes, which were also enriched in starch and sucrose metabolism and glutathione metabolism pathways. Their expression was measured by reverse transcription quantitative PCR (qRT-PCR), and the results were consistent with the transcriptome analysis, thus verifying the reliability of transcriptome data. We selected three miRNAs (miRNA858-y, miRNA171-z and a novel miRNA novel-m0005-5p) to test the relationship between miRNAs and their target genes. The activity of the GUS testing assay indicated that miRNA could decrease the GUS activity by inhibiting the expression of their target genes. Collectively, this study provides a comprehensive analysis of transcriptome and small RNA sequencing of lotus root after inoculation with Fusarium oxysporum, and we identified candidate miRNAs and their target genes for breeding strategies of Nelumbo nucifera.

Jasmonates regulate apical hook development by repressing brassinosteroid biosynthesis and signaling.

An apical hook is a special structure formed during skotomorphogenesis in dicotyledonous plant species. It is critical for protecting the shoot apical meristem from mechanical damage during seed germination and hypocotyl elongation in soil. Brassinosteroid (BR) and jasmonate (JA) phytohormones antagonistically regulate apical hook formation. However, the interrelationship between BRs and JAs in this process has not been well elucidated. Here, we reveal that JAs repress BRs to regulate apical hook development in Arabidopsis (Arabidopsis thaliana). Exogenous application of methyl jasmonate (MeJA) repressed the expression of the rate-limiting BR biosynthetic gene DWARF4 (DWF4) in a process relying on 3 key JA-dependent transcription factors, MYC2, MYC3, and MYC4. We demonstrated that MYC2 interacts with the critical BR-activated transcription factor BRASSINAZOLE RESISTANT 1 (BZR1), disrupting the association of BZR1 with its partner transcription factors, such as those of the PHYTOCHROME INTERACTING FACTOR (PIF) family and downregulating the expression of their target genes, such as WAVY ROOT GROWTH 2 (WAG2), encoding a protein kinase essential for apical hook development. Our results indicate that JAs not only repress the expression of BR biosynthetic gene DWF4 but, more importantly, attenuate BR signaling by inhibiting the transcriptional activation of BZR1 by MYC2 during apical hook development.

Brassinosteroids affect wood development and properties of Fraxinus mandshurica.

Xylem development plays a crucial role in wood formation in woody plants. In recent years, there has been growing attention towards the impact of brassinosteroids (BRs) on this xylem development. In the present study, we evaluated the dynamic variation of xylem development in Fraxinus mandshurica (female parent, M8) and a novel interspecific hybrid F. mandshurica × Fraxinus sogdiana (1601) from May to August 2020. We obtained RNA-Seq transcriptomes of three tissue types (xylem, phloem, and leaf) to identify the differences in xylem-differentially expressed genes (X-DEGs) and xylem-specifically expressed genes (X-SEGs) in M8 and 1601 variants. We then further evaluated these genes via weighted gene co-expression network analysis (WGCNA) alongside overexpressing FmCPD, a BR biosynthesis enzyme gene, in transient transgenic F. mandshurica. Our results indicated that the xylem development cycle of 1601 was extended by 2 weeks compared to that of M8. In addition, during the later wood development stages (secondary wall thickening) of 1601, an increased cellulose content (14%) and a reduced lignin content (11%) was observed. Furthermore, vessel length and width increased by 67% and 37%, respectively, in 1601 compared with those of M8. A total of 4589 X-DEGs were identified, including enzymes related to phenylpropane metabolism, galactose metabolism, BR synthesis, and signal transduction pathways. WGCNA identified hub X-SEGs involved in cellulose synthesis and BR signaling in the 1601 wood formation-related module (CESA8, COR1, C3H14, and C3H15); in contrast, genes involved in phenylpropane metabolism were significantly enriched in the M8 wood formation-related module (CCoAOMT and CCR). Moreover, overexpression of FmCPD in transient transgenic F. mandshurica affected the expression of genes associated with lignin and cellulose biosynthesis signal transduction. Finally, BR content was determined to be approximately 20% lower in the M8 xylem than in the 1601 xylem, and the exogenous application of BRs (24-epi brassinolide) significantly increased the number of xylem cell layers and altered the composition of the secondary cell walls in F. mandshurica. Our findings suggest that BR biosynthesis and signaling play a critical role in the differing wood development and properties observed between M8 and 1601 F. mandshurica.

Uncovering mechanisms governing stem growth in peanut (Arachis hypogaea L.) with varying plant heights through integrated transcriptome and metabolomics analyses

The mechanisms responsible for stem growth in peanut (Arachis hypogaea L.) cultivars with varying plant heights remain unclear, despite the significant impact of plant height on peanut yield. Therefore, this study aimed to investigate the underlying mechanisms of peanut stem growth using phenotypic, physiological, transcriptomic, and metabolomic analyses. The findings revealed that the tallest cultivar, HY33, exhibited the highest rate of stem growth and accumulated the most stem dry matter, followed by the intermediate cultivar, SH108, while the dwarf cultivar, Df216, displayed the lowest values. Furthermore, SH108 exhibited a higher harvest index, as well as superior pod and kernel yields compared to both HY33 and Df216. Transcriptome and metabolome analyses identified differentially expressed genes (DEGs) and differentially expressed metabolites (DEMs) associated with phenylpropanoid and flavonoid biosynthesis. Notably, downregulated DEGs in Df216/HY33 and Df216/SH108 included phenylalanine ammonia-lyase (PAL), caffeoyl-CoA O-methyltransferase (COMT), and ferulate-5-hydroxylase (F5H), while downregulated DEMs included p-coumaryl alcohol, chlorogenic acid, and L-epicatechin. Compared to HY33, the reduced activities of PAL, COMT, and F5H resulted in a decreased stem lignin content in Df216. Additionally, downregulated DEGs involved in gibberellin (GA) and brassinosteroid (BR) biosynthesis were identified in Df216/HY33, which contributed to the lowest levels of GA1, GA3, and BR contents in Df216. The results suggest that the dwarf phenotype arises from impaired GA and BR biosynthesis and signaling, resulting in a slower stem growth rate and reduced lignin accumulation.

Current understanding of unlocking the power of melatonin and other phytohormones to boost abiotic stress tolerance in solanaceous vegetable crops

Solanaceous vegetable crops are extensively consumed and cultivated around the world, however they are often subjected towards different abiotic stress conditions including cold, heat, drought, salt and heavy-metals toxicity. These stresses notably affect plant growth, yield, and quality. Novel Phytohormones plays a major role in managing crop responses to abiotic stress conditions, particularly those seen in Solanaceous vegetable crops. In this review, an overview of the physiological, morphological and molecular responses of Solanaceous vegetable crops to abiotic stresses, and the regulatory roles of the novel phytohormones in these responses, is furnished. Furthermore, the impact of abiotic stresses on the biosynthesis, metabolism and signaling pathways of major phytohormones, particularly melatonin (MEL), salicylic-acid (SA), jasmonic-acid (JA), strigolactones (SLs), brassinosteroids (BRs) and gamma-aminobutyric acid (GABA) is discussed. Consequently, phytohormones application remarkably boosts growth status of plant, leaf photosynthetic apparatus, root architecture system, osmolytes accumulation, and secondary metabolites production, and upregulates photosynthesis related gene expression. In addition, phytohormone regulates ascorbate-glutathione cycle and reduces cellular membrane damage, as well as maintains mineral nutrient homeostasis. Overall, the current review delivers a comprehensive overview of the recent studies on regulating roles of phytohormones for abiotic stresses in Solanaceous vegetables crops, which may serve as a valuable resource for researchers and breeders working for the enhancement of crop resilience and productivity in challenging environments.

The rice transcription factors OsHOX22 and OsHOX24 oppositely modulate the lamina joint inclination

OsHOX22 and OsHOX24 are members of the homeodomain-leucine zipper I (HD-Zip I) subfamily of transcription factors (TFs) involved in ABA-mediated salt and drought tolerance. Phylogenetic analyses resolve these TFs into the same subgroup (γ-clade). We used CRISPR/Cas9 technology to obtain two Japonica CVs. Kitaake edited rice lines (edOsHOX22 and edOsHOX24) by a non-homologous end-joining mechanism. These plants displayed opposite phenotypes in the lamina joint inclination of the second leaf of 9-day-old seedlings. The edOsHOX22 genotype presented a larger leaf angle than the wild-type (WT), resembling plants with increased endogenous brassinosteroid (BR) levels. In addition, the BR treatment repressed OsHOX22 expression in WT plants. Otherwise, the edOsHOX24 plants exhibited the opposite phenotype, and BRs induced OsHOX24 expression. This evidence suggested a mutual negative and positive regulation between OsHOX22 and OsHOX24 and the phytohormone, respectively. Besides, BR biosynthesis and signaling genes exhibited altered levels in edOsHOX22 and edOsHOX24 plants compared with controls. Notably, under abiotic stress, they agonistically modified their expression, and the ABA signaling cascade masked the BR response, closing the leaf angle in both genotypes. Our findings indicated that OsHOX22 and OsHOX24 play differential roles in the lamina joint inclination event. This study contributes two new players to the complex mechanisms involved in the leaf angle opening under different environmental cues in rice.

Plasmodesmata mediate cell-to-cell transport of brassinosteroid hormones.

Brassinosteroids (BRs) are steroidal phytohormones that are essential for plant growth, development and adaptation to environmental stresses. BRs act in a dose-dependent manner and do not travel over long distances; hence, BR homeostasis maintenance is critical for their function. Biosynthesis of bioactive BRs relies on the cell-to-cell movement of hormone precursors. However, the mechanism of the short-distance BR transport is unknown, and its contribution to the control of endogenous BR levels remains unexplored. Here we demonstrate that plasmodesmata (PD) mediate the passage of BRs between neighboring cells. Intracellular BR content, in turn, is capable of modulating PD permeability to optimize its own mobility, thereby manipulating BR biosynthesis and signaling. Our work uncovers a thus far unknown mode of steroid transport in eukaryotes and exposes an additional layer of BR homeostasis regulation in plants.