The strigolactone pathway plays a crucial role in integrating metabolic and nutritional signals in plants

Resistance to Striga parasitism through reduction of strigolactone exudation

Parasitism with Striga poses a major threat to global food production. Striga germination and growth rely on strigolactones (SLs) exuded by crop roots under phosphate (Pi)-deficient conditions, although the mechanism of this host-parasite interaction remains elusive. In this study, transcriptomic and functional analyses of sorghum treated with Pi deficiency or the SL GR245DS identify two ABC transporter G (ABCG) transporters of SL, Sorghum biocolor strigolactones transporter 1 (SbSLT1) and SbSLT2. Using AlphaFold2 and amino acid conversion mutants, we identify highly conserved amino acids in SL transport channels essential for transport function. Sorghum lines with single or double knockouts of these transporters exhibit significantly reduced SL secretion from roots, leading to decreased Striga germination and parasitism in field experiments and consequently reducing the grain loss under Striga infestation. This study thus describes the mechanism of SL exudation in monocots and defines conserved residues essential for SL transporter function, offering a potential strategy for enhancing crop resistance to Striga parasitism.

Melatonin-governed growth and metabolome divergence: Circadian and stress responses in key plant species

Melatonin, a versatile biomolecule, profoundly influences plant growth and resilience through its intricate regulation of metabolic pathways, circadian rhythms, and cellular processes. The current study elucidates melatonin's concentration-dependent biphasic effects on growth dynamics in Arabidopsis thaliana and Brassica nigra. While 50 μM melatonin optimized biomass accumulation and root elongation, higher concentrations (100 μM) elicited stress responses, underscoring its dual role as a growth promoter and stress modulator. Melatonin extended photosynthetic efficiency by modulating chlorophyll and carotenoid synthesis diurnally, offering protection against photodamage. Divergent responses between the two species, driven by species-specific metabolic reprogramming, were evident in pigment biosynthesis and antioxidant pathways. B. nigra displayed robust activation of flavonoid and phenylpropanoid pathways, cytokinin signaling, and enhanced oxidative defenses, contrasting with A. thaliana, where melatonin suppressed pigment precursors and antioxidant activation. Metabolomic analysis revealed melatonin's orchestration of hormonal crosstalk, involving auxins, gibberellins, and jasmonates, to fine-tune growth and stress adaptation. Stomatal dynamics and cell wall fortification in B. nigra highlighted melatonin's role in optimizing water-use efficiency and structural resilience under abiotic stress. Cytogenetic studies confirmed melatonin's role in safeguarding genomic integrity, regulating chromatin remodeling, and promoting DNA repair mechanisms, with B. nigra demonstrating adaptive genomic strategies under stress. Moreover, melatonin influenced critical metabolic pathways, including polyamine biosynthesis, sulfur metabolism, and nucleotide regulation, emphasizing its multifaceted impact on cellular homeostasis. These findings position melatonin as a cornerstone molecule in plant biotechnology, with potential applications in enhancing crop resilience and productivity under fluctuating environmental conditions.

SL-6 Mimic Is a Biostimulant for Chlorella sorokiniana and Enhances the Plant Biostimulant Effect of Microalgal Extract

This study aimed to evaluate the impact of a more cost-efficient strigolactone mimic SL-6 on Chlorella sorokiniana NIVA-CHL 176 growth in comparison with the strigolactone analog GR24 and the plant biostimulant functions of microalgal extracts. Three molar SL-6 concentrations were tested: 10-7 M, 10-8 M, and 10-9 M, respectively. Five parameters of microalgal growth were assessed: optical density, turbidity, biomass production, chlorophyll fluorescence, and pigment concentration. Results after 15 days of culturing revealed that the SL-6 treatments significantly enhanced biomass production (13.53% at 10-9 M), pigment synthesis, and photosystem II activity (14.38% at 10-9 M). The highest increases in pigments induced by SL-6 were 15.7% for chlorophyll a (at 10-8 M SL-6), 12.87% for chlorophyll b (at 10-9 M SL-6), 2.3% for carotenoids (at 10-8 M SL-6), and 10.78% for total pigments (at 10-8 M SL-6) per gram biomass compared to the solvent control (DMSO). Higher doses of GR24 and SL-6 (10-7 M) inhibited microalgal growth, reducing cell density, biomass production, and pigment synthesis. The microalgal extracts acted as plant biostimulants, stimulating root and shoot elongation and proton pump functioning of mung seedlings in the presence and absence of salt stress. The extracts from SL-6 biostimulated C. sorokiniana were more active as plant biostimulants than the extracts from the non-stimulated C. sorokiniana.

Multi-Omics Association Analysis of DOF Transcription Factors Involved in the Drought Resistance of Wheat Induced by Strigolactone

Drought is one of the main adverse factors affecting the growth and development of wheat. The molecular regulation pathway of Strigolactone (SLs or SL),which induces drought resistance in wheat, needs to be further clarified. In this study, SL and Tis (Strigolactone inhibitor) were sprayed on leaves to clarify the changes in wheat drought resistance and their effect on antioxidant enzyme activity, photosynthesis and other metabolic processes. However, 20 kinds of DOF transcription factors were identified by transcriptome metabolome association analysis, and they were highly enriched on chromosome 2. Moreover, the proline, glycosides, indoleacetic acid, betaine, etc., in wheat are the key factors affecting the change in the drought resistance of wheat. The study initially revealed the mechanism of the involvement of DOF in the SL regulation pathway and revealed its impact on different metabolites of wheat, thus providing a theoretical reference for the subsequent molecular verification and breeding of excellent drought-resistant varieties.

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.

Strigolactone and karrikin receptors regulate phytohormone biosynthetic and catabolic processes

KEY MESSAGE

Karrikin plays a more critical role in affecting the homeostasis of ABA and cytokinins, while strigolactones play a more critical role in influencing the homeostasis of jasmonic acid and gibberellins. Strigolactones (SLs) and karrikins (KARs) regulate plant growth and development through their crosstalk, and through the crosstalk between them and other phytohormones, such as abscisic acid (ABA) and auxin. However, how SL and KAR signaling pathways influence the levels of other phytohormones is still unknown. Here, we performed a comparative transcriptome analysis of the Arabidopsis thaliana double mutant dwarf14 karrikin-insensitive 2 (d14 kai2), deficient in SL and KAR perception, and the wild-type (WT) using their rosette leaves. Ten gene ontology terms related to phytohormones were enriched with differentially expressed genes derived from the 'd14 kai2 vs WT' comparison. Our data revealed that the levels of auxin, ABA and salicylic acid (SA) were higher in d14 and kai2 single and d14 kai2 mutant plants than in WT, which was consistent with the results of previous investigations. In contrast, the levels of cytokinins (CKs) were found to be lower in all single and double mutants than in WT. The levels of active gibberellins were lower in d14 and d14 kai2 mutants than in WT, while they were comparable in kai2 and WT plants. Similarly, the levels of jasmonic acid (JA) were lower in d14 and d14 kai2 plants, but higher in kai2 plants than in WT. Both transcriptome and qRT-PCR analyses indicated that SL and KAR signaling pathways affect the levels of auxin, SA, CKs, gibberellin 4 (GA4) and ABA by influencing the expression of their biosynthetic (in case of auxin, SA, GA4 and CKs) and catabolic (in case of ABA) genes. Collectively, our data demonstrated that KAI2 plays a more critical role in the homeostasis of ABA and CKs, while D14 plays a more critical role in the homeostasis of JA and gibberellins. Findings of this study indicate a complex and broad crosstalk among various phytohormones in plants, which can be considered for future exogenous applications and hormone engineering.

Nitrogen deficiency influences strigolactone levels in basal parts of shoots and shoot branching phenotype in Arabidopsis thaliana

Strigolactones (SLs) are allelochemicals attracting both symbiotic arbuscular mycorrhizal (AM) fungi and root parasitic plants and a novel class of phytohormones inhibiting lateral shoot branching. In general, nutrient deficiency significantly promotes SL production in roots and exudation into the rhizosphere, and also induces suppressed shoot branching phenotype in host plants of AM fungi, including rice, tomato, and maize. Nutrient deficiencies also inhibit the shoot branching in Arabidopsis thaliana (hereafter Arabidopsis), a nonhost of AM fungi, while the level of carlactone, a noncanonical SL and the SL precursor for the other SLs, was reported to be unaffected. Because Arabidopsis SLs, including CL and methyl carlactonoate, are highly unstable, relationships between SL levels and shoot branching in Arabidopsis remain elusive. Herein, we demonstrate that nitrogen deficiency increases SL levels in the basal part of shoots in Arabidopsis and lateral shoot branching appears to be strongly regulated by these SLs.

Time-resolved oxidative signal convergence across the algae-embryophyte divide

The earliest land plants faced a significant challenge in adapting to environmental stressors. Stress on land is unique in its dynamics, entailing swift and drastic changes in light and temperature. While we know that land plants share with their closest streptophyte algal relatives key components of the genetic makeup for dynamic stress responses, their concerted action is little understood. Here, we combine time-course stress profiling using photophysiology, transcriptomics on 2.7 Tbp of data, and metabolite profiling analyses on 270 distinct samples, to study stress kinetics across three 600-million-year-divergent streptophytes. Through co-expression analysis and Granger causal inference we predict a gene regulatory network that retraces a web of ancient signal convergences at ethylene signaling components, osmosensors, and chains of major kinases. These kinase hubs already integrated diverse environmental inputs since before the dawn of plants on land.

MicroRNA399s and strigolactones mediate systemic phosphate signaling between dodder-connected host plants and control association of host plants with rhizosphere microbes

A dodder (Cuscuta) often simultaneously parasitizes two or more adjacent hosts. Phosphate (Pi) deficiency is a common stress for plants, and plants often interact with soil microbes, including arbuscular mycorrhizal fungi (AMF), to cope with Pi stress. Little is known about whether dodder transmits Pi deficiency-induced systemic signals between different hosts. In this study, dodder-connected plant clusters, each composed of two tobacco (Nicotiana tabacum) plants connected by a dodder, were established, and in each cluster, one of the two tobacco plants was treated with Pi starvation. AMF colonization efficiency, rhizosphere bacterial community, and transcriptome were analyzed in the other dodder-connected Pi-replete tobacco plant to study the functions of interplant Pi signals. We found that dodder transfers Pi starvation-induced systemic signals between host plants, resulting in enhanced AMF colonization, changes of rhizosphere bacterial communities, and alteration of transcriptomes in the roots of Pi-replete plants. Importantly, genetic analyses indicated that microRNA399s (miR399s) and strigolactones suppress the systemic Pi signals and negatively affect AMF colonization in the Pi-replete plants. These findings provide new insight into the ecological role of dodder in mediating host-host and host-microbe interactions and highlight the importance of strigolactone and miR399 pathways in systemic Pi signaling.

Novel mechanisms of strigolactone-induced DWARF14 degradation in Arabidopsis thaliana

In angiosperms, the strigolactone receptor is the α/β hydrolase DWARF14 (D14) that, upon strigolactone binding, undergoes conformational changes, triggers strigolactone-dependent responses, and hydrolyses strigolactones. Strigolactone signalling involves the formation of a complex between strigolactone-bound D14, the E3-ubiquitin ligase SCFMAX2, and the transcriptional corepressors SMXL6/7/8, which become ubiquitinated and degraded by the proteasome. Strigolactone also destabilizes the D14 receptor. The current model proposes that D14 degradation occurs after ubiquitination of the SMXLs via SCFMAX2 and proteasomal degradation. Using fluorescence and luminescence assays on transgenic lines expressing D14 fused to GREEN FLUORESCENT PROTEIN or LUCIFERASE, we showed that strigolactone-induced D14 degradation may also occur independently of SCFMAX2 and/or SMXL6/7/8 through a proteasome-independent mechanism. Furthermore, strigolactone hydrolysis was not essential for triggering either D14 or SMXL7 degradation. The activity of mutant D14 proteins predicted to be non-functional for strigolactone signalling was also examined, and their capability to bind strigolactones in vitro was studied using differential scanning fluorimetry. Finally, we found that under certain conditions, the efficiency of D14 degradation was not aligned with that of SMXL7 degradation. These findings indicate a more complex regulatory mechanism governing D14 degradation than previously anticipated and provide novel insights into the dynamics of strigolactone signalling in Arabidopsis.

The role of hydrolysis in perceiving and degrading the plant hormone strigolactones

Strigolactones (SLs) perform versatile functions in plants. The different members of the α/β-hydrolase superfamily bind and hydrolyze SLs at varying rates to transduce their signal or maintain SL homeostasis. Recent work by Palayam et al. on SL-degrading carboxylesterases (CXEs) uncovers structural elements that determine the mechanism, efficiency of SL hydrolysis, and biological functions.

Strigolactones Regulate Secondary Metabolism and Nitrogen/Phosphate Signaling in Tea Plants via Transcriptional Reprogramming and Hormonal Interactions

Strigolactones (SLs) are known to regulate plant architecture formation, nitrogen (N) and phosphorus (P) responses, and secondary metabolism, but their effects in tea plants remain unclear. We demonstrated that the application of a bioactive SL analogue GR24 either to tea roots or leaves initially stimulated but later inhibited catechins, theanine, and caffeine biosynthesis. GR24 treatment also promoted the accumulation of flavonols and insoluble proanthocyanidins in a time- and dose-dependent manner. GR24 influenced flavonoid and theanine biosynthesis genes, such as up-regulating CsTT2c, CsMYB12, and CsbZIP1, modulating N-responsive and assimilation genes (CsNRT1,1, CsGSI/TS1, CsHRS1, CsPHR1, CsNLA1, and CsLBD37/38/39), and repressing N/P transport and signaling genes (CsPHO2, CsPHT1s, CsNRT2,2, CsHHO1, and CsWRKY38). GR24-induced changes in secondary metabolites were also observed in the leaves of tea plants. GR24-regulated CsLBD37a interacted with CsTT8a and CsTT2c, repressing catechins biosynthesis by interrupting MBW complex formation. GR24 regulated caffeine biosynthesis and regulator genes CsS40 and CsNAC7 and may thereby suppress caffeine production. GR24 altered the transcriptomic profiles of multiple hormone biosynthesis and signaling genes that potentially regulate tea characteristic metabolism and N/P signaling. This study provides new insights into SL-induced transcriptional reprogramming that leads to changes in N/P nutrition, secondary metabolism, and hormone signaling in tea plants.

Impact of Pristine and Aged Tire Wear Particles on Ipomoea aquatica and Rhizospheric Microbial Communities: Insights from a Long-Term Exposure Study

Tire wear particles (TWPs), generated from tire abrasion, contribute significantly to environmental contamination. The toxicity of TWPs to organisms has raised significant concerns, yet their effects on terrestrial plants remain unclear. Here, we investigated the long-term impact of pristine and naturally aged TWPs on water spinach (Ipomoea aquatica) and its rhizospheric soil. The results indicated that natural aging reduced the toxicity of TWPs, as evidenced by decreased levels of polycyclic aromatic hydrocarbons (PAHs) in soil and TWPs themselves. Consequently, aged TWPs were found to enhance the plant growth and chlorophyll content, whereas pristine TWPs increased the plant stress. Furthermore, aged TWPs improved soil organic matter (SOM) and total organic carbon (TOC), thereby boosting the microbial enzymes involved in nitrogen cycling. Metabolomic analysis revealed that aged TWPs upregulated key pathways related to carbon and nitrogen metabolism, enhancing plant growth and stress responses. Additionally, rhizosphere bacterial diversity was higher under aged TWPs, favoring nutrient-cycling taxa such as Acidobacteriota and Nitrospirota. Pristine TWPs may lead to overproliferation of certain dominant species, thereby reducing microbial diversity in soil, which could ultimately compromise the soil health. These findings contribute to a deeper understanding of the mechanisms underlying TWP toxicity in plants and highlight the necessity for further research on the impact of aged TWPs across various plant species over different exposure durations for comprehensive risk assessment.

The strigolactone receptor DWARF14 regulates flowering time in Arabidopsis

Multiple plant hormones, including strigolactone (SL), play key roles in regulating flowering time. The Arabidopsis (Arabidopsis thaliana) DWARF14 (AtD14) receptor perceives SL and recruits F-box protein MORE AXILLARY GROWTH2 (MAX2) and the SUPPRESSOR OF MAX2-LIKE (SMXL) family proteins. These interactions lead to the degradation of the SMXL repressor proteins, thereby regulating shoot branching, leaf shape, and other developmental processes. However, the molecular mechanism by which SL regulates plant flowering remains elusive. Here, we demonstrate that intact strigolactone biosynthesis and signaling pathways are essential for normal flowering in Arabidopsis. Loss-of-function mutants in both SL biosynthesis (max3) and signaling (Atd14 and max2) pathways display earlier flowering, whereas the repressor triple mutant smxl6/7/8 (s678) exhibits the opposite phenotype. Retention of AtD14 in the cytoplasm leads to its inability to repress flowering. Moreover, we show that nuclear-localized AtD14 employs dual strategies to enhance the function of the AP2 transcription factor TARGET OF EAT1 (TOE1). AtD14 directly binds to TOE1 in an SL-dependent manner and stabilizes it. In addition, AtD14-mediated degradation of SMXL7 releases TOE1 from the repressor protein, allowing it to bind to and inhibit the FLOWERING LOCUS T (FT) promoter. This results in reduced FT transcription and delayed flowering. In summary, AtD14 perception of SL enables the transcription factor TOE1 to repress flowering, providing insights into hormonal control of plant flowering.

Strigolactone signalling inhibits trehalose 6-phosphate signalling independently of BRC1 to suppress shoot branching

The phytohormone strigolactone (SL) inhibits shoot branching, whereas the signalling metabolite trehalose 6-phosphate (Tre6P) promotes branching. How Tre6P and SL signalling may interact and which molecular mechanisms might be involved remains largely unknown. Transcript profiling of Arabidopsis SL mutants revealed a cluster of differentially expressed genes highly enriched in the Tre6P pathway compared with wild-type (WT) plants or brc1 mutants. Tre6P-related genes were also differentially expressed in axillary buds of garden pea (Pisum sativum) SL mutants. Tre6P levels were elevated in the SL signalling mutant more axillary (max) growth 2 compared with other SL mutants or WT plants indicating a role of MAX2-dependent SL signalling in regulating Tre6P levels. A transgenic approach to increase Tre6P levels demonstrated that all SL mutant lines and brc1 flowered earlier, showing all of these mutants were responsive to Tre6P. Elevated Tre6P led to increased branching in WT plants but not in max2 and max4 mutants, indicating some dependency between the SL pathway and Tre6P regulation of shoot branching. By contrast, elevated Tre6P led to an enhanced branching phenotype in brc1 mutants indicating independence between BRC1 and Tre6P. A model is proposed whereby SL signalling represses branching via Tre6P and independently of the BRC1 pathway.

Strigolactones: A promising tool for nutrient acquisition through arbuscular mycorrhizal fungi symbiosis and abiotic stress tolerance

Strigolactones (SLs) constitute essential phytohormones that control pathogen defense, resilience to phosphate deficiency and abiotic stresses. Furthermore, SLs are released into the soil by roots, especially in conditions in which there is inadequate phosphate or nitrogen available. SLs have the aptitude to stimulate the root parasite plants and symbiotic cooperation with arbuscular mycorrhizal (AM) fungi in rhizosphere. The use of mineral resources, especially phosphorus (P), by host plants is accelerated by AMF, which also improves plant growth and resilience to a series of biotic and abiotic stresses. Thus, these SL treatments that promote rhizobial symbiosis are substitutes for artificial fertilizers and other chemicals, supporting ecologically friendly farming practices. Moreover, SLs have become a fascinating target for abiotic stress adaptation in plants, with an array of uses in sustainable agriculture. In this review, the biological activity has been summarized that SLs as a signaling hormone for AMF symbiosis, nutrient acquisition, and abiotic stress tolerance through interaction with other hormones. Furthermore, the processes behind the alterations in the microbial population caused by SL are clarified, emphasizing the interplay with other signaling mechanisms. This review covers the latest developments in SL studies as well as the properties of SLs on microbial populations, plant hormone transductions, interactions and abiotic stress tolerance.

OsCYP706C2 diverts rice strigolactone biosynthesis to a noncanonical pathway branch

Strigolactones exhibit dual functionality as regulators of plant architecture and signaling molecules in the rhizosphere. The important model crop rice exudes a blend of different strigolactones from its roots. Here, we identify the inaugural noncanonical strigolactone, 4-oxo-methyl carlactonoate (4-oxo-MeCLA), in rice root exudate. Comprehensive, cross-species coexpression analysis allowed us to identify a cytochrome P450, OsCYP706C2, and two methyl transferases as candidate enzymes for this noncanonical rice strigolactone biosynthetic pathway. Heterologous expression in yeast and Nicotiana benthamiana indeed demonstrated the role of these enzymes in the biosynthesis of 4-oxo-MeCLA, which, expectedly, is derived from carlactone as substrate. The oscyp706c2 mutants do not exhibit a tillering phenotype but do have delayed mycorrhizal colonization and altered root phenotype. This work sheds light onto the intricate complexity of strigolactone biosynthesis in rice and delineates its role in symbiosis and development.

Biosynthesis and signal transduction of plant growth regulators and their effects on bioactive compound production in Salvia miltiorrhiza (Danshen)

Plant growth regulators (PGRs) are involved in multiple aspects of plant life, including plant growth, development, and response to environmental stimuli. They are also vital for the formation of secondary metabolites in various plants. Salvia miltiorrhiza is a famous herbal medicine and has been used commonly for > 2000 years in China, as well as widely used in many other countries. S. miltiorrhiza is extensively used to treat cardiovascular and cerebrovascular diseases in clinical practices and has specific merit against various diseases. Owing to its outstanding medicinal and commercial potential, S. miltiorrhiza has been extensively investigated as an ideal model system for medicinal plant biology. Tanshinones and phenolic acids are primary pharmacological constituents of S. miltiorrhiza. As the growing market for S. miltiorrhiza, the enhancement of its bioactive compounds has become a research hotspot. S. miltiorrhiza exhibits a significant response to various PGRs in the production of phenolic acids and tanshinones. Here, we briefly review the biosynthesis and signal transduction of PGRs in plants. The effects and mechanisms of PGRs on bioactive compound production in S. miltiorrhiza are systematically summarized and future research is discussed. This article provides a scientific basis for further research, cultivation, and metabolic engineering in S. miltiorrhiza.

The Cooperation Regulation of Antioxidative System and Hormone Contents on Physiological Responses of Wedelia trilobata and Wedelia chinensis under Simulated Drought Environment

Drought-induced metabolic dysregulation significantly enhances the production of reactive oxygen species (ROS), which, in turn, exerts a substantial influence on the oxidation-reduction regulatory status of cells. These ROS, under conditions of drought stress, become highly reactive entities capable of targeting various plant organelles, metabolites, and molecules. Consequently, disruption affects a wide array of metabolic pathways and eventually leads to the demise of the cells. Given this understanding, this study aimed to investigate the effects of different drought stress levels on the growth and development of the invasive weed Wedelia trilobata and its co-responding native counterpart Wedelia chinensis. Both plants evolved their defense mechanisms to increase their antioxidants and hormone contents to detoxify ROS to avoid oxidative damage. Still, the chlorophyll content fluctuated and increased in a polyethylene-glycol-simulated drought. The proline content also rose in the plants, but W. chinensis showed a significant negative correlation between proline and malondialdehyde in different plant parts. Thus, W. trilobata and W. chinensis exhibited diverse or unlike endogenous hormone regulation patterns under drought conditions. Meanwhile, W. trilobata and W. chinensis pointedly increased the content of indole acetic acid and gibberellic acid in a different drought stress environment. A positive correlation was found between endogenous hormones in other plant parts, including in the roots and leaves. Both simulated and natural drought conditions exerted a significant influence on both plant species, with W. trilobata displaying superior adaptation characterized by enhanced growth, bolstered antioxidant defense mechanisms, and heightened hormonal activities.

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.

Novel Strigolactone Mimics That Modulate Photosynthesis and Biomass Accumulation in Chlorella sorokiniana

In terrestrial plants, strigolactones act as multifunctional endo- and exo-signals. On microalgae, the strigolactones determine akin effects: induce symbiosis formation with fungi and bacteria and enhance photosynthesis efficiency and accumulation of biomass. This work aims to synthesize and identify strigolactone mimics that promote photosynthesis and biomass accumulation in microalgae with biotechnological potential. Novel strigolactone mimics easily accessible in significant amounts were prepared and fully characterized. The first two novel compounds contain 3,5-disubstituted aryloxy moieties connected to the bioactive furan-2-one ring. In the second group of compounds, a benzothiazole ring is connected directly through the cyclic nitrogen atom to the bioactive furan-2-one ring. The novel strigolactone mimics were tested on Chlorella sorokiniana NIVA-CHL 176. All tested strigolactones increased the accumulation of chlorophyll b in microalgae biomass. The SL-F3 mimic, 3-(4-methyl-5-oxo-2,5-dihydrofuran-2-yl)-3H-benzothiazol-2-one (7), proved the most efficient. This compound, applied at a concentration of 10-7 M, determined a significant biomass accumulation, higher by more than 15% compared to untreated control, and improved the quantum yield efficiency of photosystem II. SL-F2 mimic, 5-(3,5-dibromophenoxy)-3-methyl-5H-furan-2-one (4), applied at a concentration of 10-9 M, improved protein production and slightly stimulated biomass accumulation. Potential utilization of the new strigolactone mimics as microalgae biostimulants is discussed.

Strigolactones and Shoot Branching: What Is the Real Hormone and How Does It Work?

There have been substantial advances in our understanding of many aspects of strigolactone regulation of branching since the discovery of strigolactones as phytohormones. These include further insights into the network of phytohormones and other signals that regulate branching, as well as deep insights into strigolactone biosynthesis, metabolism, transport, perception and downstream signaling. In this review, we provide an update on recent advances in our understanding of how the strigolactone pathway co-ordinately and dynamically regulates bud outgrowth and pose some important outstanding questions that are yet to be resolved.