A Tale of Two Sugars: Trehalose 6-Phosphate and Sucrose

2,2',4,4'-Tetrabromodiphenyl ether and copper disturbed the source-to-sink allocation of sucrose in rice through regulating the NAC23-Tre6P-SnRK1a signaling pathway

The co-occurrence of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and copper (Cu) in agricultural fields pose significant implications for crop growth and grain production. This study explored their individual and combined effects on rice crops and elucidated the underlying mechanisms combining in vivo, in vitro, and in silico investigations. Both BDE-47 and Cu inhibited shoot biomass, whereas root biomass exhibited distinct profiles: BDE-47 inhibited it, while Cu promoted it, at environmentally relevant exposure concentrations. This phenomenon was attributed to differences in sucrose transport between the source (shoot) and sink (root). Furthermore, metabolic, transcriptional, and translational analyses unveiled that this process was modulated by the NAC23-Tre6P-SnRK1a signaling pathway, with the dysfunction of fructose-1,6-diphosphate aldolase (FBA) and alterations in intracellular sucrose level serving as the crucial negative factors. Both contaminants bound to FBA, disrupting glucose signal transmission and upregulating SnRK1a expression. Additionally, BDE-47 suppressed sucrose levels, thereby reducing NAC23 activity and inhibiting sucrose transport. Conversely, Cu significantly elevated sucrose levels, mitigating the adverse effects of SnRK1a on NAC23 and enhancing sucrose transport. Interestingly, the coexistence of Cu with BDE-47 synergistically inhibited sucrose transport, further reducing root biomass and lowering the toxicity threshold of BDE-47 on rice crops. This study offered novel insights into the signaling regulatory mechanisms governing the differential impacts of BDE-47 and Cu on rice growth and yield production, facilitating more accurate assessments of their phytotoxicity and informing scientific regulatory frameworks for croplands.

Systems analysis of long-term heat stress responses in the C4 grass Setaria viridis

Many C4 plants are used as food and fodder crops and often display improved resource use efficiency compared to C3 plants. However, the response of C4 plants to future extreme conditions such as heatwaves is less understood. Here, Setaria viridis, an emerging C4 model grass, was grown under long-term high-temperature stress for 2 wk (42 °C, compared to 28 °C). This resulted in stunted growth, but surprisingly had little impact on leaf thickness, leaf area-based photosynthetic rates, and bundle sheath leakiness. Dark respiration rates increased, and there were major alterations in carbon and nitrogen metabolism in the heat-stressed plants. Abscisic acid and indole-3-acetic acid-amino acid conjugates accumulated in the heat-stressed plants, consistent with transcriptional changes. Leaf transcriptomics, proteomics, and metabolomics analyses were carried out and mapped onto the metabolic pathways of photosynthesis, respiration, carbon/nitrogen metabolism, and phytohormone biosynthesis and signaling. An in-depth analysis of correlations between transcripts and their corresponding proteins revealed strong differences between groups in the strengths and signs of correlations. Overall, many stress signaling pathways were upregulated, consistent with multiple signals leading to reduced plant growth. A systems-based model of the plant response to long-term heat stress is presented based on the oxidative stress, phytohormone, and sugar signaling pathways.

Sugar sensors in plants: Orchestrators of growth, stress tolerance, and hormonal crosstalk

Sugars, vital metabolites for cellular health, play a central role in regulating diverse intracellular pathways that control plant growth and development. They also enhance stress responses, enabling plants to endure adverse conditions. A few intracellular molecules involved in sensing the intracellular sugar content and concomitantly facilitating appropriate response (growth or survivability) are known as sugar sensors. Among the numerous sugar sensors identified in plants, this review focuses on four extensively studied sugar sensors, namely hexokinase (HXK), Sucrose non-fermenting 1-related kinase-1 (Snf1-related kinase-1 or SnRK1), Target of rapamycin (TOR), and trehalose 6-phosphate (T6P). This review explores the multifaceted functions of these sugar sensors, highlighting their critical role in balancing energy metabolism and coordinating physiological processes under optimal and adverse conditions. By analyzing their involvement in plant growth, development, and stress response, this review underscores the significance of these sensors throughout the plant life cycle. Furthermore, this review highlights the intricate interplay among these sugar sensors, demonstrating how their activities are finely tuned and interdependent. We also examined the crosstalk between these sugar sensors and phytohormones, fine-tuning plant responses to environmental stimuli. Altogether, this review elucidates the significance of sugar sensors as integrators of metabolic and hormonal signals, providing a comprehensive understanding of their pivotal roles in plant biology. This knowledge paves the way for potential agricultural innovations to enhance crop productivity and resilience in the face of climate change.

Nutrient stress triggers sugar-mediated carotenoid production in algal-bacterial interactions

This study examined the impact of co-culturing Chlorella saccharophila (UTEX247) with Exiguobacterium sp. strain AMK1 on carotenoid production under nitrate-depleted conditions and 3% CO₂ supplementation. The co-culture significantly enhanced the productivity of lutein (238.31 µg.L⁻¹d⁻¹), zeaxanthin (220.72 µg.L⁻¹d⁻¹), violaxanthin (185.42 µg.L⁻¹d⁻¹), and antheraxanthin (84.07 µg.L⁻¹d⁻¹). Compared to nitrate-repleted mono-cultures, these carotenoids increased by 3.54-fold, 4.81-fold, 12.28-fold, and 9.34-fold, respectively. The violaxanthin cycle, activated by CO₂ supplementation, resulted in higher zeaxanthin production, verified through HPLC analysis. Metabolic profiling highlighted a notable rise in sucrose, an algal-specific metabolite, in the co-culture, reflecting enhanced carbon metabolism and carotenoid synthesis. Conversely, trehalose levels were significantly higher in the bacterial mono-culture (297.77 µg.mL⁻¹) than in the co-culture (88.84 µg.mL⁻¹), showing a 1.68-fold reduction as confirmed by GC-MS/MS. This suggests trehalose as a stress marker, with its reduction indicating mutualistic interactions between algal and bacterial. Overall, the co-culture strategy emerges as a promising approach to activate unexpressed pathways, generate novel metabolites, and enhance yields of valuable carotenoids like lutein and zeaxanthin. This aligns with the principles of a circular bioeconomy, leveraging bacterial biofertilizers, valorizing CO₂, and minimizing chemical dependency, thus offering potential for biorefinery applications.

The MYC Gene RrbHLH105 Contributes to Salt Stress-Induced Geraniol in Rose by Regulating Trehalose-6-Phosphate Signalling

Rose (Rosa rugosa) is an important perfume plant, but its cultivation is significantly constrained by salt stress. Terpenes represent the most abundant volatile aromatic compounds in roses, yet little is known about how terpene metabolism responds to salt stress. In this study, salt-treated rose petals presented significant accumulation of monoterpenes, including geraniol, due to the disruption of jasmonic acid (JA) biosynthesis and signalling. Overexpression and silencing analyses revealed a MYC transcription factor involved in JA signalling (RrbHLH105) as a repressor of geraniol biosynthesis. RrbHLH105 was shown to activate the trehalose-6-phosphate synthase genes RrTPS5 and RrTPS8 by binding to the E-box (5'-CANNTG-3'). The increased trehalose-6-phosphate content and decreased geraniol content in rose petals overexpressing TPS5 or RrTPS8, along with the high accumulation of geraniol in petals where both RrbHLH105 and TPSs were cosilenced, indicate that trehalose signalling plays a role in the negative regulation of geraniol accumulation via the RrbHLH105-TPS module. In summary, the suppression of RrbHLH105 by salt stress leads to excessive geraniol accumulation through the inhibition of both RrbHLH105-mediated JA signalling and RrTPS-mediated trehalose signalling in rose petals. Additionally, this study highlights the emerging role of RrbHLH105 as a critical integrator of JA and trehalose signalling crosstalk.

Signalling and regulation of plant development by carbon/nitrogen balance

The two most abundant macronutrients in plant cells are carbon (C) and nitrogen (N). Coordination of their cellular metabolism is a fundamental factor in guaranteeing the optimal growth and development of plants. N availability and assimilation profoundly affect plant gene expression and modulate root and stem architecture, thus affecting whole plant growth and crop yield. N status also affects C fixation, as it is an important component of the photosynthetic machinery in leaves. Reciprocally, increasing C supply promotes N uptake and assimilation. There is extensive knowledge of the different mechanisms that plants use for sensing and signalling their nutritional status to regulate the assimilation, metabolism and transport of C and N. However, the crosstalk between C and N pathways has received much less attention. Plant growth and development are greatly affected by suboptimal C/N balance, which can arise from nutrient deficiencies or/and environmental cues. Mechanisms that integrate and respond to changes in this specific nutritional balance have started to arise. This review will examine the specific responses to C/N imbalance in plants by focusing on the main inorganic and organic metabolites involved, how they are sensed and transported, and the interconnection between the early signalling components and hormonal networks that underlies plants' adaptive responses.

Identification of Submergence Tolerance Loci in Dongxiang Wild Rice (DXWR) by Genetic Linkage and Transcriptome Analyses

The submergence tolerance of rice is a key factor in promoting rice direct seeding technology and resisting flood disasters. Dongxiang wild rice (DXWR) has strong submergence tolerance, but its genetic basis is still unclear. Here, we report quantitative trait loci (QTLs) analysis for hypoxic germination rate (HGR), hypoxic seedling rate (HSR), budlet submergence survival rate (BSSR) and seedling submergence survival rate (SSSR) using a linkage map in the backcross recombinant inbred lines (BRILs) that were derived from a cross of DXWR, and an indica cultivar, GZX49. A total of 20 QTLs related to submergence tolerance of rice were detected, explaining phenotypic variations ranging from 2% to 8.5%. Furthermore, transcriptome sequencing was performed on the seeds and seedlings of DXWR before and after submergence. During the seed hypoxic germination and seedling submergence stages, 6306 and 3226 differentially expressed genes (DEGs) were detected respectively. Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) analyses were conducted on these differentially expressed genes. Using genetic linkage analysis and transcriptome data, combined with qRT-PCR, sequence comparison, and bioinformatics, LOC_Os05g32820 was putatively identified as a candidate gene for qHGR5.2 co-located with HGR and SSSR. These results will provide insights into the mechanism of rice submergence tolerance and provide a basis for improving rice submergence tolerance.

Salicylic Acid Cooperates With Lignin and Sucrose Signals to Alleviate Waxy Maize Leaf Senescence Under Heat Stress

Leaf senescence induced by high temperature (HT) has become a primary factor limiting maize yield, particularly during the filling stage. Exogenous salicylic acid (SA) has emerged as an effective strategy to mitigate leaf senescence and HT-induced damage, though its underlying mechanisms remain unclear. This study investigated the regulatory mechanism of SA application on waxy maize subjected to HT during the early filling stage. Compared to HT alone, exogenous SA alleviated the inhibition of photosynthesis and oxidative damage by enhancing the activities of enzymes involved in photosynthesis and antioxidant system and modulating phytohormone metabolism and signal transduction pathways, thereby reducing leaf senescence and mitigating yield loss under HT. Transcriptomic and metabolomic analyses showed that HT downregulated most genes involved in the starch and sucrose metabolism pathway in leaves but promoted soluble sugar accumulation, which represents a plant strategy to cope with HT. Conversely, exogenous SA reversed this change and further enhanced soluble sugar accumulation in leaves. SA also regulated sugar metabolism by inhibiting trehalose-6-phosphate synthesis and activating SnRK1 to resist HT. Furthermore, SA stimulated lignin biosynthesis through the phenylpropanoid pathway, ensuring cell membrane integrity under HT. The relationship between SA signalling and plant heat tolerance was validated using a maize SA synthesis-synthetic mutant.

A Phosphate-Starvation Enhanced Purple Acid Phosphatase, GmPAP23 Mediates Intracellular Phosphorus Recycling and Yield in Soybean

Plant internal phosphorus (P) recycling is a complex process, which is vital for improving plant P use efficiency. However, the mechanisms underlying phosphate (Pi) release from internal organic-P form remains to be deciphered in crops. Here, we functionally characterised a Pi-starvation responsive purple acid phosphatase (PAP), GmPAP23 in soybean (Glycine max). GmPAP23 could hydrolyse a series of Pi-containing compounds in vitro, such as trehalose-6-phosphate and glucose-l-phosphate. Moreover, GmPAP23 overexpression led to less P distribution in soybean source organs, including mature leaves and pod shells, but more P distribution in seeds under P sufficient conditions, although no effect was observed for transgenic soybean lines with its suppression. Metabolomic analysis found that a group of P-containing metabolites exhibited differential accumulations in mature leaves between wild type (WT) and GmPAP23 overexpression lines, such as glucose-l-phosphate and trehalose-6-phosphate. Moreover, a MYB transcription factor, GmPHR14 was subsequently found to activate the transcription of GmPAP23 via directly binding to its promoter. Collectively, these findings could highlight that the GmPHR14-GmPAP23 pathway, which controls internal P recycling in soybean, and thus affect yield.

OsFKBP12 transduces the sucrose signal from OsNIN8 to the OsTOR pathway in a loosely binding manner for cell division

Previously, OsNIN8 initiated a sucrose signal for cell division in radicle and seed development in rice. Here, a set of genes was induced in starved sprouts after sucrose treatment, and 14 genes were screened between ZH11 and nin8 as reporters of sucrose signal. Expressions of reporter depended on levels of OsNIN8 in overexpression and RNAi lines. Further, OsNIN8 interacted with OsFKBP12, a regulator of TOR signal for cell division, and OsFKBP12 interacted with OsTOR (OsTORKD). However, interactions of OsFKBP12 with OsNIN8 or OsTORKD were a loose binding depending on the hydrophobicity of OsFKBP12 C-terminus in Y2H. In addition, OsFKBP12 associating with OsNIN8 was endothermic but with OsNIN8m was exothermic. Knockout OsFKBP12 reappeared nin8 phenotypes and the complementation of the knockout with C-termini of OsFKBP12 worsened the phenotypes. Treatment with TOR inhibitors caused short radicle and OsTOR RNAi repeated low seed-setting of the phenotypes. So, OsFKBP12 transduced sucrose signal from OsNIN8 to the TOR pathway.

The role of trehalose metabolism in plant stress tolerance

BACKGROUND

Trehalose is a nonreducing disaccharide containing two glucose molecules linked through an α,α-1,1-glycosidic bond. This unique chemical structure causes trehalose levels to fluctuate significantly in plants under stress, where it functions as an osmoprotectant, enhancing plant resistance to stress. Previous studies have confirmed that the trehalose synthesis pathway is widely conserved across most plants. However, the protective role of trehalose is limited only to organelles or tissues where the concentration is sufficiently high.

AIM OF REVIEW

In this review, we summarize previous reports on improving plant stress tolerance (drought, cold, heat, salt, pathogen, etc.) by applying trehalose-6-phosphate (T6P) or trehalose and manipulating the expression of trehalose metabolism-related genes. The molecular mechanisms underlying T6P, trehalose, and their related genes that regulate plant stress resistance are reviewed. More progressive studies on the spatiotemporal control of trehalose metabolism will provide a novel tool that allows for the simultaneous enhancement of crop yield and stress tolerance.

KEY SCIENTIFIC CONCEPTS OF REVIEW

We introduce the history of trehalose and discuss the possibility of trehalose and its metabolity-related genes binding to T6P to participate in stress response through unknown signaling pathways. In addition, the effects of trehalose metabolism regulation on plant growth and stress resistance were reviewed, and the molecular mechanism was fully discussed. In particular, we came up with new insights that the molecular mechanism of trehalose metabolism to enhance plant stress resistance in the future and we propose the need to use biotechnology methods to cultivate crops with stress resistance and high yield potential.

Genome-wide identification and characterization of circular RNAs for exogenous trehalose-mediated heat stress responses in tea plants (Camellia sinensis)

Background

Heat stress is one of the main environmental factors limiting the growth, yield and quality of tea plants (Camellia sinensis). Trehalose involved in plant responses to multiple adverse environmental stresses, including heat stress. However, the roles of circular RNAs (circRNAs) and their involvement in the trehalose response to heat stress remain unknown.

Methods

In this study, circRNA-sequencing was performed to analyze the characteristics of circRNAs in trehalose-induced responses to heat stress in tea plants. Kyoto Encyclopedia of Genes and Genomes enrichment analysis was used to determine the potential function of circRNAs, and the expression of differentially expressed circRNAs (DECs) and their host genes related to Non-homologous end-joining (NHEJ) and Homologous recombination (HR) were analyzed. To further explore the effect of trehalose on DNA double strand breaks (DSBs), the reactive oxygen species (ROS) contents, specially hydrogen peroxide (H2O2) and superoxide anion (O2-), in heat-stressed tea plants were investigated.

Results

A total of 11402 circRNAs were detected from CK, T (heat stress) and TT (heat stress + trehalose) samples. Among these circRNAs, 573, 620 and 550 circRNAs were identified as differentially expressed in the T vs. CK, TT vs. CK and TT vs. T comparison groups, respectively. The host genes of DECs were enriched in NHEJ and HR pathways, implying a critical role of circRNAs in DSBs repair. The expression level of circKu70-1 and circKu70-3 showed positive correlations with their host gene, ATP-dependent DNA helicase II 70 kDa subunit (CsKu70), while circKu70-2 exhibited an opposite expression trend. Similarly, circRad50 displayed a negative correlation with its host gene, DNA repair protein RAD50 (CsRad50). Notably, the expression of CsKu70 and CsRad50, which are crucial for initiating DSB repair, was decreased in the trehalose-treated (TT) samples. This finding suggests that trehalose may play a role in modulating the expression of circRNAs and their host genes involved in NHEJ and HR pathways, ultimately contributing to reduced DSB damage during heat stress. Moreover, exogenous trehalose significantly reduced H2O2 and O2- contents in tea plants under heat stress, suggesting that trehalose could mitigate heat-induced damage resulting from ROS overproduction.

Conclusion

Our results indicated that circRNAs play a crucial role in maintaining genome integrity. Specifically, they may function as molecular hubs that respond to changes of the levels of H2O2 and O2- induced by trehalose, and subsequently regulate the DSBs mediated by their host genes. This, in turn, further impacts genome stability, ultimately enhancing heat tolerance in tea plants. Our findings provided new insight into the potential applications of trehalose as an agrochemical in tea plants and revealed the potential role of circRNAs in tea plants heat tolerance.

Starch metabolism in guard cells: At the intersection of environmental stimuli and stomatal movement

Starch metabolism in guard cells plays a central role in regulating stomatal movement in response to light, elevated ambient CO2 and potentially other abiotic and biotic factors. Here, we discuss how various guard cell signal transduction pathways converge to promote rearrangements in guard cell starch metabolism for efficient stomatal responses, an essential physiological process that sustains plant productivity and stress tolerance. We suggest manipulation of guard cell starch dynamics as a previously overlooked strategy to improve stomatal behavior under changing environmental conditions.

Characterization and Transcriptomic Analysis of Sorghum EIN/EIL Family and Identification of Their Roles in Internode Maturation

Ethylene-insensitive 3/Ethylene-insensitive3-like proteins (EIN3/EIL) represent a group of transcription factors critical for the ethylene signaling transduction that manipulate downstream ethylene-responsive genes, thereby regulating plant growth, development, and stress responses. However, the identification, evolution, and divergence of the EIL family remain to be studied in Sorghum bicolor. Here, we identified eight SbEILs, which were expanded due to whole-genome-duplication (WGD) events. Characterization of the protein sequences and expression atlas demonstrates that the WGD-duplicated SbEILs could become divergent due to the differential expression patterns, rather than domain and motif architectures. Comparative expression analysis was performed between the RNA-seq data sets of internodes from several sorghum cultivars to understand the potential roles of SbEIL members in internode elongation and maturation. Our results identified SbEIL3 and 7 (the latter as a homolog of OsEIL7/OsEIL1) to be the highly expressed SbEIL genes in sorghum internodes and revealed a potential functional link between SbEIL7 and internode maturation. The co-expression analysis and comparative expression analysis with ethylene-regulated gene sets found that SbEIL7 was co-regulated with a set of ubiquitin-related protein degradation genes, suggesting possible involvement of SbEIL7 in protein degradation and processing during the post-anthesis stages. Altogether, our findings lay a foundation for future functional studies of ethylene signaling-mediated gene regulation and improvement of sorghum internode development.

Direct and indirect responses of the Arabidopsis transcriptome to an induced increase in trehalose 6-phosphate

Trehalose 6-phosphate (Tre6P) is an essential signal metabolite that regulates the level of sucrose, linking growth and development to the metabolic status. We hypothesized that Tre6P plays a role in mediating the regulation of gene expression by sucrose. To test this, we performed transcriptomic profiling on Arabidopsis (Arabidopsis thaliana) plants that expressed a bacterial TREHALOSE 6-PHOSPHATE SYNTHASE (TPS) under the control of an ethanol-inducible promoter. Induction led to a 4-fold rise in Tre6P levels, a concomitant decrease in sucrose, significant changes (FDR ≤ 0.05) of over 13,000 transcripts, and 2-fold or larger changes of over 5,000 transcripts. Comparison with nine published responses to sugar availability allowed some of these changes to be linked to the rise in Tre6P, while others were probably due to lower sucrose or other indirect effects. Changes linked to Tre6P included repression of photosynthesis-related gene expression and induction of many growth-related processes including ribosome biogenesis. About 500 starvation-related genes are known to be induced by SUCROSE-NON-FERMENTING-1-RELATED KINASE 1 (SnRK1). They were largely repressed by Tre6P in a manner consistent with SnRK1 inhibition by Tre6P. SnRK1 also represses many genes that are involved in biosynthesis and growth. These responded to Tre6P in a more complex manner, pointing toward Tre6P interacting with other C-signaling pathways. Additionally, elevated Tre6P modified the expression of genes encoding regulatory subunits of the SnRK1 complex and TPS class II and FCS-LIKE ZINC FINGER proteins that are thought to modulate SnRK1 function and genes involved in circadian, TARGET OF RAPAMYCIN, light, abscisic acid, and other hormone signaling.

Possible Mechanism of Sucrose and Trehalose-6-Phosphate in Regulating the Secondary Flower on the Strong Upright Spring Shoots of Blueberry Planted in Greenhouse

Secondary flowering is the phenomenon in which a tree blooms twice or more times a year. Along with the development of blueberry (Vaccinium corymbosum L.) fruits in spring, a large number of secondary flowers on the strong upright spring shoots were noticed in blueberries planted in the greenhouse. To reveal the cause and possible regulatory mechanism of the phenomenon, we clarified the phenological characteristics of flower bud differentiation and development on the spring shoots by combining phenological phenotype with anatomical observation. Furthermore, the changes in carbohydrates, trehalose-6-phosphate (Tre6P), and the relationship among the key enzyme regulatory genes for Tre6P metabolism and the key regulatory genes for flower formation during the differentiation process of apical buds and axillary buds were investigated. The results showed that the process of flower bud differentiation and flowering of apical and axillary buds was consistent, accompanied by a large amount of carbohydrate consumption. This process was positively correlated with the expression trends of VcTPS1/2, VcSnRK1, VcFT, VcLFY2, VcSPL43, VcAP1, and VcDAM in general, and negatively correlated with that of VcTPP. In addition, there is a certain difference in the differentiation progress of flower buds between the apical and axillary buds. Compared with axillary buds, apical buds had higher contents of sucrose, fructose, glucose, Tre6P, and higher expression levels of VcTPS2, VcFT, VcSPL43, and VcAP1. Moreover, VcTPS1 and VcTPS2 were more closely related to the physiological substances (sucrose and Tre6P) in axillary bud and apical bud differentiation, respectively. It was suggested that sucrose and trehalose-6-phosphate play a crucial role in promoting flower bud differentiation in strong upright spring shoots, and VcTPS1 and VcTPS2 might play a central role in these activities. Our study provided substantial sight for further study on the mechanism of multiple flowering of blueberries and laid a foundation for the regulation and utilization of the phenomenon of multiple flowering in a growing season of perennial woody plants.

Integrated physiological, transcriptomic and metabolomic analyses reveal the mechanism of peanut kernel weight reduction under waterlogging stress

Waterlogging stress (WS) hinders kernel development and directly reduces peanut yield; however, the mechanism of kernel filling in response to WS remains unknown. The waterlogging-sensitive variety Huayu 39 was subjected to WS for 3 days at 7 days after the gynophores touched the ground (DAG). We found that WS affected kernel filling at 14, 21, and 28 DAG. WS decreased the average filling rate and kernel dry weight, while transcriptome sequencing and widely targeted metabolomic analysis revealed that WS inhibited the gene expression in starch and sucrose metabolism, which reduced sucrose input and transformation ability. Additionally, genes related to ethylene and melatonin synthesis and the accumulation of tryptophan and methionine were upregulated in response to WS. WS upregulated the expression of the gene encoding tryptophan decarboxylase (AhTDC), and overexpression of AhTDC in Arabidopsis significantly reduced the seed length, width, and weight. Therefore, WS reduced the kernel-filling rate, leading to a reduction in the 100-kernel weight. This survey informs the development of measures that alleviate the negative impact of WS on peanut yield and quality and provides a basis for exploring high-yield and high-quality cultivation, molecular-assisted breeding, and waterlogging prevention in peanut farming.

Receptor-like cytoplasmic kinase 58 reduces tolerance of maize seedlings to low magnesium via promoting H2O2 over-accumulation

KEY MESSAGE

ZmRLCK58, a negative growth regulator, reduces tolerance of maize seedlings to low Mg via enhancing H2O2 accumulation in the shoot. Magnesium (Mg) deficiency is one of critical limiting factors for crop production in widespread acidic soils worldwide. However, the molecular mechanism of crop response to Mg deficiency is still largely unclear. Here, we found higher concentrations of H2O2, soluble sugars, and starch (1.5-, 1.9-, and 1.4-fold, respectively) in the shoot of low-Mg-treated maize seedlings, compared with Mg sufficient plants under hydroponic culture. Consistent with over-accumulation of H2O2, transcriptome profiling revealed significant enrichment of 175 differentially expressed genes (DEGs) in "response to oxygen-containing compound" out of 641 DEGs in the shoot under low Mg. Among 175 DEGs, a down-regulated receptor-like cytoplasmic kinase ZmRLCK58 underwent a recent duplication event before Poaceae divergence and was highly expressed in the maize shoot. ZmRLCK58 overexpression enhanced H2O2 accumulation in shoots by 21.3% and 29.8% under control and low-Mg conditions, respectively, while reducing biomass accumulation compared with wild-type plants. Low Mg further led to 39.7% less starch accumulation in the ZmRLCK58 overexpression shoot and lower Mg utilization efficiency. Compared with wild-type plants, overall down-regulated expression of genes related to response to carbohydrate, photosynthesis, H2O2 metabolic, oxidation-reduction, and ROS metabolic processes in ZmRLCK58 overexpression lines preconditioned aforementioned physiological alterations. Together, ZmRLCK58, as a negative growth regulator, reduces tolerance of maize seedlings to low Mg via enhancing H2O2 accumulation.

Genome-wide transcript expression analysis reveals major chickpea and lentil genes associated with plant branching

The search for elite cultivars with better architecture has been a demand by farmers of the chickpea and lentil crops, which aims to systematize their mechanized planting and harvesting on a large scale. Therefore, the identification of genes associated with the regulation of the branching and architecture of these plants has currently gained great importance. Herein, this work aimed to gain insight into transcriptomic changes of two contrasting chickpea and lentil cultivars in terms of branching pattern (little versus highly branched cultivars). In addition, we aimed to identify candidate genes involved in the regulation of shoot branching that could be used as future targets for molecular breeding. The axillary and apical buds of chickpea cultivars Blanco lechoso and FLIP07-318C, and lentil cultivars Castellana and Campisi, considered as little and highly branched, respectively, were harvested. A total of 1,624 and 2,512 transcripts were identified as differentially expressed among different tissues and contrasting cultivars of chickpea and lentil, respectively. Several gene categories were significantly modulated such as cell cycle, DNA transcription, energy metabolism, hormonal biosynthesis and signaling, proteolysis, and vegetative development between apical and axillary tissues and contrasting cultivars of chickpea and lentil. Based on differential expression and branching-associated biological function, ten chickpea genes and seven lentil genes were considered the main players involved in differentially regulating the plant branching between contrasting cultivars. These collective data putatively revealed the general mechanism and high-effect genes associated with the regulation of branching in chickpea and lentil, which are potential targets for manipulation through genome editing and transgenesis aiming to improve plant architecture.

Tissue- and time-dependent metabolite profiles during early grain development under normal and high night-time temperature conditions

BACKGROUND

Wheat grain development in the first few days after pollination determines the number of endosperm cells that influence grain yield potential and is susceptible to various environmental conditions, including high night temperatures (HNTs). Flag leaves and seed-associated bracts (glumes, awn, palea, and lemma) provide nutrients to the developing seed. However, the specific metabolic roles of these tissues are uncertain, especially their dynamics at different developmental stages and the time in a day. Tissue- and time-dependent metabolite profiling may hint at the metabolic roles of tissues and the mechanisms of how HNTs affect daytime metabolic status in early grain development.

RESULTS

The metabolite profiles of flag leaf, bract, seed (embryo and endosperm), and entire spike were analyzed at 12:00 (day) and 23:00 (night) on 2, 4, and 6 days after fertilization under control and HNT conditions. The metabolite levels in flag leaves and bracts showed day/night oscillations, while their behaviors were distinct between the tissues. Some metabolites, such as sucrose, cellobiose, and succinic acid, showed contrasting oscillations in the two photosynthetic tissues. In contrast, seed metabolite levels differed due to the days after fertilization rather than the time in a day. The seed metabolite profile altered earlier in the HNT than in the control condition, likely associated with accelerated grain development caused by HNT. HNT also disrupted the day/night oscillation of sugar accumulation in flag leaves and bracts.

CONCLUSIONS

These results highlight distinct metabolic roles of flag leaves and bracts during wheat early seed development. The seed metabolite levels are related to the developmental stages. The early metabolic events in the seeds and the disruption of the day/night metabolic cycle in photosynthetic tissues may partly explain the adverse effects of HNT on grain yield.

Sensing and regulation of C and N metabolism - novel features and mechanisms of the TOR and SnRK1 signaling pathways

Carbon (C) and nitrogen (N) metabolisms are tightly integrated to allow proper plant growth and development. Photosynthesis is dependent on N invested in chlorophylls, enzymes, and structural components of the photosynthetic machinery, while N uptake and assimilation rely on ATP, reducing equivalents, and C-skeletons provided by photosynthesis. The direct connection between N availability and photosynthetic efficiency allows the synthesis of precursors for all metabolites and building blocks in plants. Thus, the capacity to sense and respond to sudden changes in C and N availability is crucial for plant survival and is mediated by complex yet efficient signaling pathways such as TARGET OF RAPAMYCIN (TOR) and SUCROSE-NON-FERMENTING-1-RELATED PROTEIN KINASE 1 (SnRK1). In this review, we present recent advances in mechanisms involved in sensing C and N status as well as identifying current gaps in our understanding. We finally attempt to provide new perspectives and hypotheses on the interconnection of diverse signaling pathways that will allow us to understand the integration and orchestration of the major players governing the regulation of the CN balance.

TaTPS11 enhances wheat cold resistance by regulating source-sink factor

The presence of sugar in plant tissue can lead to an increase in the osmotic pressure within cells, a decrease in the freezing point of plants, and protection against ice crystal damage to the tissue. Trehalose is closely related to sucrose, which comprises the largest proportion of sugar and has become a hot topic of research in recent years. Our previous studies have confirmed that a key trehalose synthesis gene, TaTPS11, from the cold-resistant winter wheat DM1, could enhance the cold resistance of plants by increasing sugar content. However, the underlying mechanism behind this phenomenon remains unclear. In this study, we cloned TaTPS11-6D, edited TaTPS11-6D using CRISPR/Cas9 technology and transformed 'Fielder' to obtain T2 generation plants. We screened out OE3-3 and OE8-7 lines with significantly higher cold resistance than that of 'Fielder' and Cri 4-3 edited lines with significantly lower cold resistance than that of 'Fielder'. Low temperature storage limiting factors were measured for OE3-3, OE8-7 and Cri 4-3 treated at different temperatures.The results showed that TaTPS11-6D significantly increased the content of sugar in plants and the transfer of sugar from source to storage organs under cold conditions. The TaTPS11-6D significantly increased the levels of salicylic, jasmonic, and abscisic acids while also significantly decreasing the level of gibberellic acid. Our research improves the model of low temperature storage capacity limiting factor.

The AaERF64-AaTPPA module participates in cold acclimatization of Actinidia arguta (Sieb. et Zucc.) Planch ex Miq

Actinidia arguta (A. arguta, kiwiberry) is a perennial deciduous vine with a strong overwintering ability. We hypothesized that trehalose metabolism, which plays a pivotal role in the stress tolerance of plants, may be involved in the cold acclimatization of A. arguta. Transcriptome analysis showed that the expression of AaTPPA, which encodes a trehalose-6-phosphate phosphatase (TPP), was upregulated in response to low temperatures. AaTPPA expression levels were much higher in lateral buds, roots, and stem cambia than in leaves in autumn. In AaTPPA-overexpressing (OE) Arabidopsis thaliana (A. thaliana), trehalose levels were 8-11 times higher than that of the wild type (WT) and showed different phenotypic characteristics from WT and OtsB (Escherichia coli TPP) overexpressing lines. AaTPPA-OE A. thaliana exhibited significantly higher freezing tolerance than WT and OtsB-OE lines. Transient overexpression of AaTPPA in A. arguta leaves increased the scavenging ability of reactive oxygen species (ROS) and the soluble sugar and proline contents. AaERF64, an ethylene-responsive transcription factor, was induced by ethylene treatment and bound to the GCC-box of the AaTPPA promoter to activate its expression. AaTPPA expression was also induced by abscisic acid. In summary, the temperature decrease in autumn is likely to induce AaERF64 expression through an ethylene-dependent pathway, which consequently upregulates AaTPPA expression, leading to the accumulation of osmotic protectants such as soluble sugars and proline in the overwintering tissues of A. arguta.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11032-024-01475-8.

Molecular mechanism of trehalose 6-phosphate inhibition of the plant metabolic sensor kinase SnRK1

SUCROSE-NON-FERMENTING1-RELATED PROTEIN KINASE1 (SnRK1), a central plant metabolic sensor kinase, phosphorylates its target proteins, triggering a global shift from anabolism to catabolism. Molecular modeling revealed that upon binding of KIN10 to GEMINIVIRUS REP-INTERACTING KINASE1 (GRIK1), KIN10's activation T-loop reorients into GRIK1's active site, enabling its phosphorylation and activation. Trehalose 6-phosphate (T6P) is a proxy for cellular sugar status and a potent inhibitor of SnRK1. T6P binds to KIN10, a SnRK1 catalytic subunit, weakening its affinity for GRIK1. Here, we investigate the molecular details of T6P inhibition of KIN10. Molecular dynamics simulations and in vitro phosphorylation assays identified and validated the T6P binding site on KIN10. Under high-sugar conditions, T6P binds to KIN10, blocking the reorientation of its activation loop and preventing its phosphorylation and activation by GRIK1. Under these conditions, SnRK1 maintains only basal activity levels, minimizing phosphorylation of its target proteins, thereby facilitating a general shift from catabolism to anabolism.

Metabolite-mediated adaptation of crops to drought and the acquisition of tolerance

Drought is one of the major and growing threats to agriculture productivity and food security. Metabolites are involved in the regulation of plant responses to various environmental stresses, including drought stress. The complex drought tolerance can be ascribed to several simple metabolic traits. These traits could then be used for detecting the genetic architecture of drought tolerance. Plant metabolomes show dynamic differences when drought occurs during different developmental stages or upon different levels of drought stress. Here, we reviewed the major and most recent findings regarding the metabolite-mediated plant drought response. Recent progress in the development of drought-tolerant agents is also discussed. We provide an updated schematic overview of metabolome-driven solutions for increasing crop drought tolerance and thereby addressing an impending agricultural challenge.

Unraveling Key Factors for Hypoxia Tolerance in Contrasting Varieties of Cotton Rose by Comparative Morpho-physiological and Transcriptome Analysis

The cotton rose (Hibiscus mutabilis) is a plant species commonly found in tropical and subtropical regions. It is remarkably resilient to waterlogging stress; however, the underlying mechanism behind this trait is yet unknown. This study used hypoxia-tolerant "Danbanhong" (DBH) and more hypoxia-sensitive "Yurui" (YR) genotypes and compared their morpho-physiological and transcriptional responses to hypoxic conditions. Notably, DBH had a higher number of adventitious roots (20.3) compared to YR (10.0), with longer adventitious roots in DBH (18.3 cm) than in YR (11.2 cm). Furthermore, the formation of aerenchyma was 3-fold greater in DBH compared to YR. Transcriptomic analysis revealed that DBH had more rapid transcriptional responses to hypoxia than YR. Identification of a greater number of differentially expressed genes (DEGs) for aerenchyma, adventitious root formation and development, and energy metabolism in DBH supported that DBH had better morphological and transcriptional adaptation than YR. DEG functional enrichment analysis indicated the involvement of variety-specific biological processes in adaption to hypoxia. Plant hormone signaling transduction, MAPK signaling pathway and carbon metabolism played more pronounced roles in DBH, whereas the ribosome genes were specifically induced in YR. These results show that effective multilevel coordination of adventitious root development and aerenchyma, in conjunction with plant hormone signaling and carbon metabolism, is required for increased hypoxia tolerance. This study provides new insights into the characterization of morpho-physiological and transcriptional responses to hypoxia in H. mutabilis, shedding light on the molecular mechanisms of its adaptation to hypoxic environments.

Overexpression of oilseed rape trehalose-6-phosphate synthesis gene BnaC02.TPS8 confers sensitivity to low nitrogen and high sucrose-induced anthocyanin accumulation in Arabidopsis

MAIN CONCLUSION

Overexpression of BnaC02.TPS8 increased low N and high sucrose-induced anthocyanin accumulation. Anthocyanin plays a crucial role in safeguarding photosynthetic tissues against high light, UV radiation, and oxidative stress. Their accumulation is triggered by low nitrogen (N) stress and elevated sucrose levels in Arabidopsis. Trehalose-6-phosphate (T6P) serves as a pivotal signaling molecule, sensing sucrose availability, and carbon (C) metabolism. However, the mechanisms governing the regulation of T6P synthase (TPS) genes responsible for anthocyanin accumulation under conditions of low N and high sucrose remain elusive. In a previous study, we demonstrated the positive impact of a cytoplasm-localized class II TPS protein 'BnaC02.TPS8' on photosynthesis and seed yield improvement in Brassica napus. The present research delves into the biological role of BnaC02.TPS8 in response to low N and high sucrose. Ectopic overexpression of BnaC02.TPS8 in Arabidopsis seedlings resulted in elevated shoot T6P levels under N-sufficient conditions, as well as an increased carbon-to-nitrogen (C/N) ratio, sucrose accumulation, and starch storage under low N conditions. Overexpression of BnaC02.TPS8 in Arabidopsis heightened sensitivity to low N stress and high sucrose levels, accompanied by increased anthocyanin accumulation and upregulation of genes involved in flavonoid biosynthesis and regulation. Metabolic profiling revealed increased levels of intermediate products of carbon metabolism, as well as anthocyanin and flavonoid derivatives in BnaC02.TPS8-overexpressing Arabidopsis plants under low N conditions. Furthermore, yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) analyses demonstrated that BnaC02.TPS8 interacts with both BnaC08.TPS9 and BnaA01.TPS10. These findings contribute to our understanding of how TPS8-mediated anthocyanin accumulation is modulated under low N and high sucrose conditions.

Genome-Wide Analysis of Trehalose-6-Phosphate Phosphatase Gene Family and Their Expression Profiles in Response to Abiotic Stress in Groundnut

Trehalose-6-phosphate phosphatase (TPP) is a pivotal enzyme in trehalose biosynthesis which plays an essential role in plant development and in the abiotic stress response. However, little is currently known about TPPs in groundnut. In the present study, a total of 16 AhTPP genes were identified, and can be divided into three phylogenetic subgroups. AhTPP members within the same subgroups generally displayed similar exon-intron structures and conserved motifs. Gene collinearity analysis revealed that segmental duplication was the primary factor driving the expansion of the AhTPP family. An analysis of the upstream promoter region of AhTPPs revealed eight hormone- and four stress-related responsive cis-elements. Transcriptomic analysis indicated high expression levels of AhTPP genes in roots or flowers, while RT-qPCR analysis showed upregulation of the six tested genes under different abiotic stresses, suggesting that AhTPPs play roles in growth, development, and response to various abiotic stresses. Subcellular localization analysis showed that AhTPP1A and AhTPP5A were likely located in both the cytoplasm and the nucleus. To further confirm their functions, the genes AhTPP1A and AhTPP5A were individually integrated into yeast expression vectors. Subsequent experiments demonstrated that yeast cells overexpressing these genes displayed increased tolerance to osmotic and salt stress compared to the control group. This study will not only lay the foundation for further study of AhTPP gene functions, but will also provide valuable gene resources for improving abiotic stress tolerance in groundnut and other crops.

The roles of non-structural carbohydrates in fruiting: a review focusing on mango (Mangifera indica)

Reproductive development of fruiting trees, including mango (Mangifera indica L.), is limited by non-structural carbohydrates. Competition for sugars increases with cropping, and consequently, vegetative growth and replenishment of starch reserves may reduce with high yields, resulting in interannual production variability. While the effect of crop load on photosynthesis and the distribution of starch within the mango tree has been studied, the contribution of starch and sugars to different phases of reproductive development requires attention. This review focuses on mango and examines the roles of non-structural carbohydrates in fruiting trees to clarify the repercussions of crop load on reproductive development. Starch buffers the plant's carbon availability to regulate supply with demand, while sugars provide a direct resource for carbon translocation. Sugar signalling and interactions with phytohormones play a crucial role in flowering, fruit set, growth, ripening and retention, as well as regulating starch, sugar and secondary metabolites in fruit. The balance between the leaf and fruit biomass affects the availability and contributions of starch and sugars to fruiting. Crop load impacts photosynthesis and interactions between sources and sinks. As a result, the onset and rate of reproductive processes are affected, with repercussions for fruit size, composition, and the inter-annual bearing pattern.

GRIK phosphorylates and activates KIN10 which also promotes its degradation

The sensor kinase Sucrose Non-fermenting-1-Related Kinase 1 (SnRK1) plays a central role in energy and metabolic homeostasis. KIN10 is a major catalytic (α) kinase subunit of SnRK1 regulated by transcription, posttranslational modification, targeted protein degradation, and its subcellular localization. Geminivirus Rep Interacting Kinase 1 and 2 (GRIK1 and 2) are immediate upstream kinases of KIN10. In the transient protein expression assays carried out in Nicotiana benthamiana (N. benthamiana) leaves, GRIK1 not only phosphorylates KIN10 but also simultaneously initiates its degradation. Posttranslational GRIK-mediated KIN10 degradation is dependent on both GRIK kinase activity and phosphorylation of the KIN10 T-loop. KIN10 proteins are significantly enriched in the grik1-1 grik2-1 double mutant, consistent with the transient assays in N. benthamiana. Interestingly. Among the enriched KIN10 proteins from grik1-1 grik2-1, is a longer isoform, putatively derived by alternative splicing which is barely detectable in wild-type plants. The reduced stability of KIN10 upon phosphorylation and activation by GRIK represents a mechanism that enables the KIN10 activity to be rapidly reduced when the levels of intracellular sugar/energy are restored to their set point, representing an important homeostatic control that prevents a metabolic overreaction to low-sugar conditions. Since GRIKs are activating kinases of KIN10, KIN10s in the grik1 grik2 double null mutant background remain un-phosphorylated, with only their basal level of activity, are more stable, and therefore increase in abundance, which also explains the longer isoform KIN10L which is a minor isoform in wild type is clearly detected in the grik1 grik2 double mutant.

Chalkiness and premature controlled by energy homeostasis in OsNAC02 Ko-mutant during vegetative endosperm development

BACKGROUND

Chalkiness is a common phenotype induced by various reasons, such as abiotic stress or the imbalance of starch synthesis and metabolism during the development period. However, the reason mainly for one gene losing its function such as NAC (TFs has a large family in rice) which may cause premature is rarely known to us.

RESULTS

The Ko-Osnac02 mutant demonstrated an obviously early maturation stage compared to the wild type (WT) with 15 days earlier. The result showed that the mature endosperm of Ko-Osnac02 mutant exhibited chalkiness, characterized by white-core and white-belly in mature endosperm. As grain filling rate is a crucial factor in determining the yield and quality of rice (Oryza sativa, ssp. japonica), it's significant that mutant has a lower amylose content (AC) and higher soluble sugar content in the mature endosperm. Interestingly among the top DEGs in the RNA sequencing of N2 (3DAP) and WT seeds revealed that the OsBAM2 (LOC_Os10g32810) expressed significantly high in N2 mutant, which involved in Maltose up-regulated by the starch degradation. As Prediction of Protein interaction showed in the chalky endosperm formation in N2 seeds (3 DAP), seven genes were expressed at a lower-level which should be verified by a heatmap diagrams based on DEGs of N2 versus WT. The Tubulin genes controlling cell cycle are downregulated together with the MCM family genes MCM4 ( ↓), MCM7 ( ↑), which may cause white-core in the early endosperm development. In conclusion, the developing period drastically decreased in the Ko-Osnac02 mutants, which might cause the chalkiness in seeds during the early endosperm development.

CONCLUSIONS

The gene OsNAC02 which controls a great genetic co-network for cell cycle regulation in early development, and KO-Osnac02 mutant shows prematurity and white-core in endosperm.

Sucrose homeostasis: Mechanisms and opportunity in crop yield improvement

Sugar homeostasis is a critical feature of biological systems. In humans, raised and dysregulated blood sugar is a serious health issue. In plants, directed changes in sucrose homeostasis and allocation represent opportunities in crop improvement. Plant tissue sucrose varies more than blood glucose and is found at higher concentrations (cytosol and phloem ca. 100 mM v 3.9-6.9 mM for blood glucose). Tissue sucrose varies with developmental stage and environment, but cytosol and phloem exhibit tight sucrose control. Sucrose homeostasis is a consequence of the integration of photosynthesis, synthesis of storage end-products such as starch, transport of sucrose to sinks and sink metabolism. Trehalose 6-phosphate (T6P)-SnRK1 and TOR play central, still emerging roles in regulating and coordinating these processes. Overall, tissue sucrose levels are more strongly related to growth than to photosynthesis. As a key sucrose signal, T6P regulates sucrose levels, transport and metabolic pathways to coordinate source and sink at a whole plant level. Emerging evidence shows that T6P interacts with meristems. With careful targeting, T6P manipulation through exploiting natural variation, chemical intervention and genetic modification is delivering benefits for crop yields. Regulation of cereal grain set, filling and retention may be the most strategically important aspect of sucrose allocation and homeostasis for food security.

Cytochrome c levels affect the TOR pathway to regulate growth and metabolism under energy-deficient conditions

Mitochondrial function is essential for plant growth, but the mechanisms involved in adjusting growth and metabolism to changes in mitochondrial energy production are not fully understood. We studied plants with reduced expression of CYTC-1, one of two genes encoding the respiratory chain component cytochrome c (CYTc) in Arabidopsis, to understand how mitochondria communicate their status to coordinate metabolism and growth. Plants with CYTc deficiency show decreased mitochondrial membrane potential and lower ATP content, even when carbon sources are present. They also exhibit higher free amino acid content, induced autophagy, and increased resistance to nutritional stress caused by prolonged darkness, similar to plants with triggered starvation signals. CYTc deficiency affects target of rapamycin (TOR)-pathway activation, reducing S6 kinase (S6K) and RPS6A phosphorylation, as well as total S6K protein levels due to increased protein degradation via proteasome and autophagy. TOR overexpression restores growth and other parameters affected in cytc-1 mutants, even if mitochondrial membrane potential and ATP levels remain low. We propose that CYTc-deficient plants coordinate their metabolism and energy availability by reducing TOR-pathway activation as a preventive signal to adjust growth in anticipation of energy exhaustion, thus providing a mechanism by which changes in mitochondrial activity are transduced to the rest of the cell.

GhTPPA_2 enhancement of tobacco sugar accumulation and drought tolerance

Trehalose metabolism plays an important role in plant growth and response to abiotic stress. Trehalose-6-phosphate (Tre6P) can help regulate sugar homeostasis and act as an indication signal for intracellular sugar levels. Crop productivity can be greatly increased by altering the metabolic level of endogenous trehalose in plants, which can optimize the source-sink connection. In this study, the upland cotton GhTPP protein family was first homologously compared and 24 GhTPP genes were found. Transcriptome analysis revealed that GhTPP members had obvious tissue expression specificity. Among them, GhTPPA_2 (Gh_A12G223300.1) was predominantly expressed in leaves and bolls. The results of subcellular localization showed that GhTPPA_2 is localized in the chloroplast. Via PlantCare, we analyzed the promoters and found that the expression of GhTPPA_2 may be induced by light, abiotic stress, and hormones such as abscisic acid, ethylene, salicylic acid and jasmonic acid. In addition, GhTPPA_2 was overexpressed (TPPAoe) in tobacco, and we found that the TPPase activity of TPPAoe tobacco increased by 66 %. Soluble sugar content increased by 39 % and starch content increased by 27 %. Whereas, the transgenic tobacco had obvious growth advantages under 100 mM mannitol stress. Transcriptome sequencing results showed that the differential genes between TPPAoe and control were considerably enriched in functions related to photosynthesis, phosphate group metabolism, and carbohydrate metabolism. This study shows that GhTPPA_2 is involved in regulating sugar metabolism, improving soluble sugar accumulation and drought stress tolerance of tobacco, which provides theoretical basis for research on high yield and drought tolerance of crops.

The maturation profile triggers differential expression of sugar metabolism genes in melon fruits

Melons are commercially important crops that requires specific quality attributes for successful commercialization, including accumulation of sugars, particularly sucrose. This trait can be influenced by various factors, such as the type of ripening. Cucumis melo L. is an ideal species for studying sugar metabolism because it has both climacteric and non-climacteric cultivars. Thus, this study aimed to examine the gene expression of sucrose metabolism candidates using RT-qPCR, in conjunction with postharvest physiological analyzes and high-performance liquid chromatography-based sugar quantification, in the melon cultivars 'Gaúcho' (climacteric) and 'Eldorado' (non-climacteric). The results showed that sucrose synthase 1 played a role in the synthesis and accumulation of sucrose in both cultivars, whereas sucrose synthase 2 was more highly expressed in 'Gaúcho', contributing to lower hexose content. Invertase inhibitor 1 was more highly expressed in 'Eldorado' and may be involved in sugar-induced maturation. Neutral α-galactosidase had distinct functions, playing a role in substrate synthesis for the growth of young 'Eldorado' fruits, whereas in mature 'Gaúcho' fruits it participated in the metabolism of raffinose family oligosaccharides for sucrose accumulation. The expression of trehalose-6-phosphate synthase genes indicated a greater involvement of these enzymes in the sugar regulation in 'Gaúcho' melons. These findings shed light on the intraspecific differences related to fruit quality attributes in different types of maturation and contribute to a deeper understanding of the underlying molecular mechanisms involved in the metabolism of sugars in melons, which can inform breeding programs aimed at improving fruit quality attributes in this crop.

Melatonin-mediated regulation of autophagy is independent of ABA under drought stress in sensitive variety of Gossypium hirsutum L

Autophagy is a highly conserved process that plays a crucial role in adaptation of plants to stress conditions. Melatonin and abscisic acid (ABA) share an antagonistic relationship; however, both are reported to elevate autophagy individually. Here, we report that melatonin alleviates drought stress effects like wilting and stunted growth in 18-day-old plants of drought-sensitive variety of cotton (Gossypium hirsutum L.) and improves the plant growth, chlorophyll content, photosynthetic efficiency, and sugar metabolism and transport. Melatonin priming increased the endogenous melatonin content (5.02-times) but decreased the ABA (2.63-times) by reducing NCED3 expression as compared to unprimed plants under drought. Also, elevated expression of ATG8c and ATG8f correlated with higher lipidated-ATG8 levels and modulation of RAPTOR1 suggesting a higher occurrence of autophagy and regulation of plant growth in primed stressed plants. Additionally, decreased TPS63 and increased TPP22 expression could have lowered the accumulation of trehalose-6-P (T6P) in primed stressed plants thus contributing to autophagy progression. Priming also enhanced the expression of MAPK6 and RAF18, and increased the transcript/protein levels of SnRK2.6 and KIN10, which is pointing towards melatonin's beneficial effect on autophagy under drought. Despite higher ABA content, elevated TPS63 and downregulated TPP22 could have hindered autophagy induction in unprimed stressed plants. Although fluridone treatment reduced the ABA content, the expression of SnRK2.6 and KIN10 remained unaltered in fluridone-treated and untreated primed plants indicating the ABA-independent expression. These results suggest that the melatonin-mediated activation of MAPK contributes to the ABA-independent activation of SnRK2, consequently, SnRK1 and autophagy under drought.

Induced responses to the wheat pathogen: Tan Spot-(Pyrenophora tritici-repentis) in wheat (Triticum aestivum) focus on changes in defence associated and sugar metabolism

INTRODUCTION

Tan Spot (TS) disease of wheat is caused by Pyrenophora tritici-repentis (Ptr), where most of the yield loss is linked to diseased flag leaves. As there are no fully resistant cultivars available, elucidating the responses of wheat to Ptr could inform the derivation of new resistant genotypes.

OBJECTIVES

The study aimed to characterise the flag-leaf metabolomes of two spring wheat cultivars (Triticum aestivum L. cv. PF 080719 [PF] and cv. Fundacep Horizonte [FH]) following challenge with Ptr to gain insights into TS disease development.

METHODS

PF and FH plants were inoculated with a Ptr strain that produces the necrotrophic toxin ToxA. The metabolic changes in flag leaves following challenge (24, 48, 72, and 96 h post-inoculation [hpi]) with Ptr were investigated using untargeted flow infusion ionisation-high resolution mass spectroscopy (FIE-HRMS).

RESULTS

Both cultivars were susceptible to Ptr at the flag-leaf stage. Comparisons of Ptr- and mock-inoculated plants indicated that a major metabolic shift occurred at 24 hpi in FH, and at 48 hpi in PF. Although most altered metabolites were genotype specific, they were linked to common pathways; phenylpropanoid and flavonoid metabolism. Alterations in sugar metabolism as well as in glycolysis and glucogenesis pathways were also observed. Pathway enrichment analysis suggested that Ptr-triggered alterations in chloroplast and photosynthetic machinery in both cultivars, especially in FH at 96 hpi. In a wheat-Ptr interactome in integrative network analysis, "flavone and flavonol biosynthesis" and "starch and sucrose metabolism" were targeted as the key metabolic processes underlying PF-FH-Ptr interactions.

CONCLUSION

These observations suggest the potential importance of flavone and flavonol biosynthesis as well as bioenergetic shifts in susceptibility to Ptr. This work highlights the value of metabolomic approaches to provide novel insights into wheat pathosystems.

Genome-wide identification of TPS and TPP genes in cultivated peanut (Arachis hypogaea) and functional characterization of AhTPS9 in response to cold stress

Introduction

Trehalose is vital for plant metabolism, growth, and stress resilience, relying on Trehalose-6-phosphate synthase (TPS) and Trehalose-6-phosphate phosphatase (TPP) genes. Research on these genes in cultivated peanuts (Arachis hypogaea) is limited.

Methods

This study employed bioinformatics to identify and analyze AhTPS and AhTPP genes in cultivated peanuts, with subsequent experimental validation of AhTPS9's role in cold tolerance.

Results

In the cultivated peanut genome, a total of 16 AhTPS and 17 AhTPP genes were identified. AhTPS and AhTPP genes were observed in phylogenetic analysis, closely related to wild diploid peanuts, respectively. The evolutionary patterns of AhTPS and AhTPP genes were predominantly characterized by gene segmental duplication events and robust purifying selection. A variety of hormone-responsive and stress-related cis-elements were unveiled in our analysis of cis-regulatory elements. Distinct expression patterns of AhTPS and AhTPP genes across different peanut tissues, developmental stages, and treatments were revealed, suggesting potential roles in growth, development, and stress responses. Under low-temperature stress, qPCR results showcased upregulation in AhTPS genes (AhTPS2-5, AhTPS9-12, AhTPS14, AhTPS15) and AhTPP genes (AhTPP1, AhTPP6, AhTPP11, AhTPP13). Furthermore, AhTPS9, exhibiting the most significant expression difference under cold stress, was obviously induced by cold stress in cultivated peanut, and AhTPS9-overexpression improved the cold tolerance of Arabidopsis by protect the photosynthetic system of plants, and regulates sugar-related metabolites and genes.

Discussion

This comprehensive study lays the groundwork for understanding the roles of AhTPS and AhTPP gene families in trehalose regulation within cultivated peanuts and provides valuable insights into the mechanisms related to cold stress tolerance.

Rapid genomic evolution in Brassica rapa with bumblebee selection in experimental evolution

BACKGROUND

Insect pollinators shape rapid phenotypic evolution of traits related to floral attractiveness and plant reproductive success. However, the underlying genomic changes remain largely unknown despite their importance in predicting adaptive responses to natural or to artificial selection. Based on a nine-generation experimental evolution study with fast cycling Brassica rapa plants adapting to bumblebees, we investigate the genomic evolution associated with the previously observed parallel phenotypic evolution. In this current evolve and resequencing (E&R) study, we conduct a genomic scan of the allele frequency changes along the genome in bumblebee-pollinated and hand-pollinated plants and perform a genomic principal component analysis (PCA).

RESULTS

We highlight rapid genomic evolution associated with the observed phenotypic evolution mediated by bumblebees. Controlling for genetic drift, we observe significant changes in allelic frequencies at multiple loci. However, this pattern differs according to the replicate of bumblebee-pollinated plants, suggesting putative non-parallel genomic evolution. Finally, our study underlines an increase in genomic variance implying the putative involvement of multiple loci in short-term pollinator adaptation.

CONCLUSIONS

Overall, our study enhances our understanding of the complex interactions between pollinator and plants, providing a stepping stone towards unravelling the genetic basis of plant genomic adaptation to biotic factors in the environment.

Flooding-adaptive root and shoot traits in rice

Wetland plants, including rice (Oryza spp.), have developed multiple functional adaptive traits to survive soil flooding, partial submergence or even complete submergence. In waterlogged soils and under water, diffusion of O2 and CO2 is extremely slow with severe impacts on photosynthesis and respiration. As a response to shallow floods or rising floodwater, several rice varieties, including deepwater rice, elongate their stems to keep their leaves above the water surface so that photosynthesis can occur unhindered during partial submergence. In stark contrast, some other varieties hardly elongate even if they become completely submerged. Instead, their metabolism is reduced to an absolute minimum so that carbohydrates are conserved enabling fast regrowth once the floodwater recedes. This review focuses on the fascinating functional adaptive traits conferring tolerance to soil flooding, partial or complete submergence. We provide a general analysis of these traits focusing on molecular, anatomical and morphological, physiological and ecological levels. Some of these key traits have already been introgressed into modern high-yielding genotypes improving flood tolerance of several cultivars used by millions of farmers in Asia. However, with the ongoing changes in climate, we propose that even more emphasis should be placed on improving flood tolerance of rice by breeding for rice that can tolerate longer periods of complete submergence or stagnant flooding. Such tolerance could be achieved via additional tissues; i.e. aquatic adventitious roots relevant during partial submergence, and leaves with higher underwater photosynthesis caused by a longer gas film retention time.

Oligosaccharide production and signaling correlate with delayed flowering in an Arabidopsis genotype grown and selected in high [CO2]

Since industrialization began, atmospheric CO2 ([CO2]) has increased from 270 to 415 ppm and is projected to reach 800-1000 ppm this century. Some Arabidopsis thaliana (Arabidopsis) genotypes delayed flowering in elevated [CO2] relative to current [CO2], while others showed no change or accelerations. To predict genotype-specific flowering behaviors, we must understand the mechanisms driving flowering response to rising [CO2]. [CO2] changes alter photosynthesis and carbohydrates in plants. Plants sense carbohydrate levels, and exogenous carbohydrate application influences flowering time and flowering transcript levels. We asked how organismal changes in carbohydrates and transcription correlate with changes in flowering time under elevated [CO2]. We used a genotype (SG) of Arabidopsis that was selected for high fitness at elevated [CO2] (700 ppm). SG delays flowering under elevated [CO2] (700 ppm) relative to current [CO2] (400 ppm). We compared SG to a closely related control genotype (CG) that shows no [CO2]-induced flowering change. We compared metabolomic and transcriptomic profiles in these genotypes at current and elevated [CO2] to assess correlations with flowering in these conditions. While both genotypes altered carbohydrates in response to elevated [CO2], SG had higher levels of sucrose than CG and showed a stronger increase in glucose and fructose in elevated [CO2]. Both genotypes demonstrated transcriptional changes, with CG increasing genes related to fructose 1,6-bisphosphate breakdown, amino acid synthesis, and secondary metabolites; and SG decreasing genes related to starch and sugar metabolism, but increasing genes involved in oligosaccharide production and sugar modifications. Genes associated with flowering regulation within the photoperiod, vernalization, and meristem identity pathways were altered in these genotypes. Elevated [CO2] may alter carbohydrates to influence transcription in both genotypes and delayed flowering in SG. Changes in the oligosaccharide pool may contribute to delayed flowering in SG. This work extends the literature exploring genotypic-specific flowering responses to elevated [CO2].

Functions of sucrose and trehalose 6-phosphate in controlling plant development

Plants exhibit enormous plasticity in regulating their architecture to be able to adapt to a constantly changing environment and carry out vital functions such as photosynthesis, anchoring, and nutrient uptake. Phytohormones play a role in regulating these responses, but sugar signalling mechanisms are also crucial. Sucrose is not only an important source of carbon and energy fuelling plant growth, but it also functions as a signalling molecule that influences various developmental processes. Trehalose 6-phosphate (Tre6P), a sucrose-specific signalling metabolite, is emerging as an important regulator in plant metabolism and development. Key players involved in sucrose and Tre6P signalling pathways, including MAX2, SnRK1, bZIP11, and TOR, have been implicated in processes such as flowering, branching, and root growth. We will summarize our current knowledge of how these pathways shape shoot and root architecture and highlight how sucrose and Tre6P signalling are integrated with known signalling networks in shaping plant growth.

Leaf senescence attributes: the novel and emerging role of sugars as signaling molecules and the overlap of sugars and hormones signaling nodes

Sugars are the primary products of photosynthesis and play multiple roles in plants. Although sugars are usually considered to be the building blocks of energy storage and carbon transport molecules, they have also gradually come to be acknowledged as signaling molecules that can initiate senescence. Senescence is an active and essential process that occurs at the last developmental stage and corresponds to programmed degradation of: cells, tissues, organs, and entire organisms. It is a complex process involving: numerous biochemical changes, transporters, genes, and transcription factors. The process is controlled by multiple developmental signals, among which sugar signals are considered to play a vital role; however, the regulatory pathways involved are not fully understood. The dynamic mechanistic framework of sugar accumulation has an inconsistent effect on senescence through the sugar signaling pathway. Key metabolizing enzymes produce different sugar signals in response to the onset of senescence. Diverse sugar signal transduction pathways and a variety of sugar sensors are involved in controlling leaf senescence. This review highlights the processes underlying initiation of sugar signaling and crosstalk between sugars and hormones signal transduction pathways affecting leaf senescence. This summary of the state of current knowledge across different plants aids in filling knowledge gaps and raises key questions that remain to be answered with respect to regulation of leaf senescence by sugar signaling pathways.

Curcumin-loaded porous particles functionalized with pH-responsive cell-penetrating peptide for colorectal cancer targeted drug delivery

The anticancer properties of curcumin have been broadly examined in several shapes, such as nanoparticles and nanocomposite structures. Despite its benefits, curcumin also has some disadvantages, including rapid metabolism, poor absorption, and rapid systemic excretion. Therefore, numerous strategies have been used to increase curcumin's bioavailability. One of these approaches is the use of porous particles like aerogels as drug carriers. Aerogels are special due to their peculiar physical structure. They have a high specific surface area, a significant amount of porosity, and a solid composition, which make them a good choice for drug delivery systems. In the present study, a pH-sensitive aerogel was constructed and evaluated for targeted drug delivery of curcumin to colon cancer. To control the release of curcumin, trehalose was used as a coating agent, and PLP (poly(l-lysine isophthalamide)) was used as a targeted drug delivery agent. PLP is a pseudo-peptidic polymer that increases the cell permeability. In order to investigate and compare the synthesized aerogel before and after loading curcumin and coating with trehalose, physicochemical characterization analyses were performed. Finally, the efficacy of the final formulation was evaluated on HT29 colon cells using the cell bioavailability test. The results indicated the successful synthesis of the aerogel with porous structure with solitary cavities. The trehalose coating performed well, preventing drug release at lower pH but allowing the drug to be released at its intended site. The designed curcumin-loaded porous particles functionalized with PLP showed significant efficacy due to increasing penetration of curcumin into cells, and has potential for use as a new drug carrier with dual effectivity in cancer therapy.

Genetic architecture of source-sink-regulated senescence in maize

Source and sink interactions play a critical but mechanistically poorly understood role in the regulation of senescence. To disentangle the genetic and molecular mechanisms underlying source-sink-regulated senescence (SSRS), we performed a phenotypic, transcriptomic, and systems genetics analysis of senescence induced by the lack of a strong sink in maize (Zea mays). Comparative analysis of genotypes with contrasting SSRS phenotypes revealed that feedback inhibition of photosynthesis, a surge in reactive oxygen species, and the resulting endoplasmic reticulum (ER) stress were the earliest outcomes of weakened sink demand. Multienvironmental evaluation of a biparental population and a diversity panel identified 12 quantitative trait loci and 24 candidate genes, respectively, underlying SSRS. Combining the natural diversity and coexpression networks analyses identified 7 high-confidence candidate genes involved in proteolysis, photosynthesis, stress response, and protein folding. The role of a cathepsin B like protease 4 (ccp4), a candidate gene supported by systems genetic analysis, was validated by analysis of natural alleles in maize and heterologous analyses in Arabidopsis (Arabidopsis thaliana). Analysis of natural alleles suggested that a 700-bp polymorphic promoter region harboring multiple ABA-responsive elements is responsible for differential transcriptional regulation of ccp4 by ABA and the resulting variation in SSRS phenotype. We propose a model for SSRS wherein feedback inhibition of photosynthesis, ABA signaling, and oxidative stress converge to induce ER stress manifested as programed cell death and senescence. These findings provide a deeper understanding of signals emerging from loss of sink strength and offer opportunities to modify these signals to alter senescence program and enhance crop productivity.

The trehalose 6-phosphate phosphatase family in plants

Trehalose 6-phosphate (Tre6P), the intermediate of trehalose biosynthesis, is an essential signalling metabolite linking plant growth and development to carbon metabolism. While recent work has focused predominantly on the enzymes that produce Tre6P, little is known about the proteins that catalyse its degradation, the trehalose 6-phosphate phosphatases (TPPs). Often occurring in large protein families, TPPs exhibit cell-, tissue- and developmental stage-specific expression patterns, suggesting important regulatory functions in controlling local levels of Tre6P and trehalose as well as Tre6P signalling. Furthermore, growing evidence through gene expression studies and transgenic approaches shows that TPPs play an important role in integrating environmental signals with plant metabolism. This review highlights the large diversity of TPP isoforms in model and crop plants and identifies how modulating Tre6P metabolism in certain cell types, tissues, and at different developmental stages may promote stress tolerance, resilience and increased crop yield.

Circadian regulation of metabolism across photosynthetic organisms

Circadian regulation produces a biological measure of time within cells. The daily cycle in the availability of light for photosynthesis causes dramatic changes in biochemical processes in photosynthetic organisms, with the circadian clock having crucial roles in adaptation to these fluctuating conditions. Correct alignment between the circadian clock and environmental day-night cycles maximizes plant productivity through its regulation of metabolism. Therefore, the processes that integrate circadian regulation with metabolism are key to understanding how the circadian clock contributes to plant productivity. This forms an important part of exploiting knowledge of circadian regulation to enhance sustainable crop production. Here, we examine the roles of circadian regulation in metabolic processes in source and sink organ structures of Arabidopsis. We also evaluate possible roles for circadian regulation in root exudation processes that deposit carbon into the soil, and the nature of the rhythmic interactions between plants and their associated microbial communities. Finally, we examine shared and differing aspects of the circadian regulation of metabolism between Arabidopsis and other model photosynthetic organisms, and between circadian control of metabolism in photosynthetic and non-photosynthetic organisms. This synthesis identifies a variety of future research topics, including a focus on metabolic processes that underlie biotic interactions within ecosystems.

Natural variation of warm temperature-induced raffinose accumulation identifies TREHALOSE-6-PHOSPHATE SYNTHASE 1 as a modulator of thermotolerance

High-temperature stress limits plant growth and reproduction. Exposure to high temperature, however, also elicits a physiological response, which protects plants from the damage evoked by heat. This response involves a partial reconfiguration of the metabolome including the accumulation of the trisaccharide raffinose. In this study, we explored the intraspecific variation of warm temperature-induced raffinose accumulation as a metabolic marker for temperature responsiveness with the aim to identify genes that contribute to thermotolerance. By combining raffinose measurements in 250 Arabidopsis thaliana accessions following a mild heat treatment with genome-wide association studies, we identified five genomic regions that were associated with the observed trait variation. Subsequent functional analyses confirmed a causal relationship between TREHALOSE-6-PHOSPHATE SYNTHASE 1 (TPS1) and warm temperature-dependent raffinose synthesis. Moreover, complementation of the tps1-1 null mutant with functionally distinct TPS1 isoforms differentially affected carbohydrate metabolism under more severe heat stress. While higher TPS1 activity was associated with reduced endogenous sucrose levels and thermotolerance, disruption of trehalose 6-phosphate signalling resulted in higher accumulation of transitory starch and sucrose and was associated with enhanced heat resistance. Taken together, our findings suggest a role of trehalose 6-phosphate in thermotolerance, most likely through its regulatory function in carbon partitioning and sucrose homoeostasis.

The rice SnRK family: biological roles and cell signaling modules

Stimulus-activated signaling pathways orchestrate cellular responses to control plant growth and development and mitigate the effects of adverse environmental conditions. During this process, signaling components are modulated by central regulators of various signal transduction pathways. Protein phosphorylation by kinases is one of the most important events transmitting signals downstream, via the posttranslational modification of signaling components. The plant serine and threonine kinase SNF1-related protein kinase (SnRK) family, which is classified into three subgroups, is highly conserved in plants. SnRKs participate in a wide range of signaling pathways and control cellular processes including plant growth and development and responses to abiotic and biotic stress. Recent notable discoveries have increased our understanding of how SnRKs control these various processes in rice (Oryza sativa). In this review, we summarize current knowledge of the roles of OsSnRK signaling pathways in plant growth, development, and stress responses and discuss recent insights. This review lays the foundation for further studies on SnRK signal transduction and for developing strategies to enhance stress tolerance in plants.

Multilayered regulation of developmentally programmed pre-anthesis tip degeneration of the barley inflorescence

Leaf and floral tissue degeneration is a common feature in plants. In cereal crops such as barley (Hordeum vulgare L.), pre-anthesis tip degeneration (PTD) starts with growth arrest of the inflorescence meristem dome, which is followed basipetally by the degeneration of floral primordia and the central axis. Due to its quantitative nature and environmental sensitivity, inflorescence PTD constitutes a complex, multilayered trait affecting final grain number. This trait appears to be highly predictable and heritable under standardized growth conditions, consistent with a developmentally programmed mechanism. To elucidate the molecular underpinnings of inflorescence PTD, we combined metabolomic, transcriptomic, and genetic approaches to show that barley inflorescence PTD is accompanied by sugar depletion, amino acid degradation, and abscisic acid responses involving transcriptional regulators of senescence, defense, and light signaling. Based on transcriptome analyses, we identified GRASSY TILLERS1 (HvGT1), encoding an HD-ZIP transcription factor, as an important modulator of inflorescence PTD. A gene-edited knockout mutant of HvGT1 delayed PTD and increased differentiated apical spikelets and final spikelet number, suggesting a possible strategy to increase grain number in cereals. We propose a molecular framework that leads to barley PTD, the manipulation of which may increase yield potential in barley and other related cereals.