Exogenous Strigolactones Research Articles

Functions of exogenous strigolactone application and strigolactone biosynthesis genes GhMAX3/GhMAX4b in response to drought tolerance in cotton (Gossypium hirsutum L.)

BackgroundDrought stress markedly constrains plant growth and diminishes crop productivity. Strigolactones (SLs) exert a beneficial influence on plant resilience to drought conditions. Nevertheless, the specific function of SLs in modulating cotton’s response to drought stress remains to be elucidated.ResultsIn this study, we assess the impact of exogenous SL (rac-GR24) administration at various concentrations (0, 1, 5, 10, 20 µM) on cotton growth during drought stress. The findings reveal that cotton seedlings treated with 5 µM exogenous SL exhibit optimal mitigation of growth suppression induced by drought stress. Treatment with 5 µM exogenous SL under drought stress conditions enhances drought tolerance in cotton seedlings by augmenting photosynthetic efficiency, facilitating stomatal closure, diminishing reactive oxygen species (ROS) generation, alleviating membrane lipid peroxidation, enhancing the activity of antioxidant enzymes, elevating the levels of osmoregulatory compounds, and upregulating the expression of drought-responsive genes. The suppression of cotton SL biosynthesis genes, MORE AXILLARY GROWTH 3 (GhMAX3) and GhMAX4b, impairs the drought tolerance of cotton. Conversely, overexpression of GhMAX3 and GhMAX4b in respective Arabidopsis mutants ameliorates the drought-sensitive phenotype in these mutants.ConclusionThese observations underscore that SLs significantly bolster cotton’s resistance to drought stress.

Exogenous strigolactones alleviate low-temperature stress in peppers seedlings by reducing the degree of photoinhibition.

The growth and yield of pepper, a typical temperature-loving vegetable, are limited by low-temperature environments. Using low-temperature sensitive 'Hangjiao No. 4' (Capsicum annuum L.) as experimental material, this study analyzed the changes in plant growth and photosynthesis under different treatments: normal control (NT), low-temperature stress alone (LT), low-temperature stress in strigolactone pretreated plants (SL_LT), and low-temperature stress in strigolactone biosynthesis inhibitor pretreated plants (Tis_LT). SL pretreatment increased the net photosynthetic rate (Pn) and PSII actual photochemical efficiency (φPSII), reducing the inhibition of LT on the growth of pepper by 17.44% (dry weight of shoot). Due to promoting the accumulation of carotenoids, such as lutein, and the de-epoxidation of the xanthophyll cycle [(Z + A)/(Z + A + V)] by strigolactone after long-term low-temperature stress (120h), non-photochemical quenching (NPQ) of pepper was increased to reduce the excess excitation energy [(1-qP)/NPQ] and the photoinhibition degree (Fv/Fm) of pepper seedlings under long-term low-temperature stress was alleviated. Twelve cDNA libraries were constructed from pepper leaves by transcriptome sequencing. There were 8776 differentially expressed genes (DEGs), including 4473 (51.0%) upregulated and 4303 (49.0%) downregulated genes. Gene ontology pathway annotation showed that based on LT, the DEGs of SL_LT and Tis_LT were significantly enriched in the cellular component, which is mainly related to the photosystem and thylakoids. Further analysis of the porphyrin and chlorophyll biosynthesis, carotenoid biosynthesis, photosynthesis-antenna protein, and photosynthetic metabolic pathways and the Calvin cycle under low-temperature stress highlighted 18, 15, 21, 29, and 31 DEGs for further study, which were almost all highly expressed under SL_LT treatment and moderately expressed under LT treatment, whereas Tis_LT showed low expression. The positive regulatory effect of SLs on the low-temperature tolerance of pepper seedlings was confirmed. This study provided new insights for the development of temperature-tolerant pepper lines through breeding programs.

Strigolactone enhances tea plant adaptation to drought and Phyllosticta theicola petch by regulating caffeine content via CsbHLH80

Strigolactones (SLs) play crucial roles in both plant growth and stress responses. However, their impact on the secondary metabolites of woody plants remains elusive. Here, we found that exogenous strigolactone analogue GR24 positively regulates tea plant flavor secondary metabolites, concurrently inhibiting caffeine biosynthesis and promoting the accumulation of caffeine catabolic pathway products. In this process, SL directly or indirectly inhibits the expression of CsSAMSs by inducing CsbHLH80, thereby reducing caffeine biosynthesis. Furthermore, CsbHLH80 enhances caffeine degradation, leading to increased allantoin. Under normal conditions, heightened allantoin reduces abscisic acid (ABA) accumulation. This inhibition reverses under drought stress. Increased ABA significantly enhances tea plant tolerance to both drought and Phyllosticta theicola Petch. In summary, this study offers novel insights for improving tea plant adaptation and quality in arid regions, particularly emphasizing the selection of stress-tolerant varieties and the refinement of production measures with a focus on high-quality production and environmentally friendly biological control methods.

Integrated transcriptomic and metabolomic analyses provide insights into the response of tobacco axillary buds to exogenous strigolactone

Integrated transcriptomic and metabolomic analyses provide insights into the response of tobacco axillary buds to exogenous strigolactone

The role of strigolactones in resistance to environmental stress in plants.

Abiotic stress impairs plant growth and development, thereby causing low yield and inferior quality of crops. Increasing studies reported that strigolactones (SL) are plant hormones that enhance plant stress resistance by regulating plant physiological processes and gene expressions. In this review, we introduce the response and regulatory role of SL in salt, drought, light, heat, cold and cadmium stresses in plants. This review also discusses how SL alleviate the damage of abiotic stress in plants, furthermore, introducing the mechanisms of SL enhancing plant stress resistance at the genetic level. Under abiotic stress, the exogenous SL analog GR24 can induce the biosynthesis of SL in plants, and endogenous SL can alleviate the damage caused by abiotic stress. SL enhanced the stress resistance of plants by protecting photosynthesis, enhancing the antioxidant capacity of plants and promoting the symbiosis between plants and arbuscular mycorrhiza (AM). SL interact with abscisic acid (ABA), salicylic acid (SA), auxin, cytokinin (CK), jasmonic acid (JA), hydrogen peroxide (H2O2) and other signal molecules to jointly regulate plant stress resistance. Lastly, both the importance of SL and their challenges for future work are outlined in order to further elucidate the specific mechanisms underlying the roles of SL in plant responses to abiotic stress.

Regulatory Mechanisms of Strigolactones on the Development of Lateral Branches in Cucumber

Cucumber (Cucumis sativus L.) belongs to the cucumber genus of the Cucurbitaceae family, and the selection of cultivars with minimal or no lateral branches can enhance the cultivation management efficiency. The growth of lateral branches is inhibited by strigolactone. To investigate the regulatory mechanism of strigolactone on the lateral branch development in cucumber, the cultivar LZ1 exhibiting multiple lateral branches was selected as the experimental material. The axillae of the plants were infiltrated with 1, 5, and 10 μmol·L−1 germination releaser 24 (GR24) at the four- to five-leaf stage. It was identified that 1 μmol·L−1 GR24 exhibited the most potent inhibitory effect on cucumber lateral branches. Additionally, exogenous strigolactone decreased the auxin content in the apical bud and axillae and increased the auxin content in the stem. This inhibited polar auxin transport in the axillary bud and promoted polar auxin transport in the apical bud. The content of strigolactone in the axilla region of cucumbers was elevated, whereas the synthesis and expression of cytokinin in the same area were reduced. A low concentration of GR24 induced the expression of cucumber branched 1 (csbrc1), whereas a high concentration of GR24 downregulated the expression of cucumber lateral suppressor (cscls) and blind (csblind), which inhibited the growth of cucumber lateral branches.

Exogenous strigolactone enhanced the drought tolerance of pepper (Capsicum chinense) by mitigating oxidative damage and altering the antioxidant mechanism.

Exogenous SL positively regulates pepper DS by altering the root morphology, photosynthetic character, antioxidant enzyme activity, stomatal behavior, and SL-related gene expression. Drought stress (DS) has always been a problem for the growth and development of crops, causing significant negative impacts on crop productivity. Strigolactone (SL) is a newly discovered class of plant hormones that are involved in plants' growth and development and environmental stresses. However, the role of SL in response to DS in pepper remains unknown. DS considerably hindered photosynthetic pigments content, damaged root architecture system, and altered antioxidant machinery. In contrast, SL application significantly restored pigment concentration modified root architecture system, and increased relative chlorophyll content (SPAD). Additionally, SL treatment reduced oxidative damage by reducing hydrogen peroxide (H2O2) (24-57%) and malondialdehyde (MDA) (79-89%) accumulation in pepper seedlings. SL-pretreated pepper seedlings showed significant improvement in antioxidant enzyme activity, proline accumulation, and soluble sugar content. Furthermore, SL-related genes (CcSMAX2, CcSMXL6, and CcSMXL3) were down-regulated under DS. These findings suggest that the foliar application of SL can alleviate the adverse effects of drought tolerance by up-regulating chlorophyll content and activating antioxidant defense mechanisms.

Exogenous strigolactone improves the cadmium accumulation in Solanum nigrum var. humile

AbstractThe effects of exogenous strigolactone (using strigolactone analog GR24) on the cadmium (Cd) accumulation in Solanum nigrum var. humile were studied by a pot experiment. The Cd treatment (0.1 mg/L) inhibited the growth of S. nigrum var. humile, indicating that 0.1 mg/L produced the stress to S. nigrum var. humile. Spraying GR24 at 1 μmol/L did not change plant dry biomass, increased the photosynthetic pigment content and catalase activity, and decreased the peroxidase activity under Cd stress. By contrast, spraying GR24 at 2 μmol/L had no significant effects on these parameters. The superoxide dismutase activity was decreased by GR24 at 1 μmol/L, but increased by GR24 at 2 μmol/L. Nevertheless, both GR24 at 1 and 2 μmol/L increased the Cd contents, bioconcentration factors, and Cd extractions in various plant organs. Compared to Cd treatment, GR24 at 1 and 2 μmol/L increased the shoot Cd extraction by 20.0% and 14.5%, respectively. So, application of exogenous strigolactone could improve the phytoremediation capacity of S. nigrum var. humile. Correlation and grey relational analyses showed that the root Cd content, shoot Cd content, and root Cd extraction were the top three parameters closely related to the shoot Cd extraction. These findings suggest that exogenous strigolactone can effectively promote the Cd accumulation in S. nigrum var. humile, presenting a promising solution to enhance its phytoremediation capacity.

Physiological and transcriptomic analyses reveal mechanisms of exogenous strigolactones to regulate cold tolerance in litchi fruit

Strigolactones (SLs) are a class of carotenoid-derived phytohormones that play diverse biological functions in plants. In the current study, we conducted physiological and transcriptomic analysis to explore the effects of two different concentrations (0.1 and 1.0 μM) of GR24, a synthetic analogue of SLs, on chilling injury (CI) and related mechanisms in litchi fruit during refrigeration at 4 °C. The results showed that 0.1 μM GR24 (GR24–0.1) dipping treatment retarded the advancement of browning and red loss in litchi pericarp during refrigeration. GR24–0.1 treatment ameliorated oxidative stress and restrained membrane deterioration, as manifested by lowered reactive oxygen species (ROS) production, relative electrolyte leakage (REL) and malondialdehyde (MDA) content. GR24–0.1 treatment inhibited the enhancement of polyphenol oxidase (PPO) and peroxidase (POD) activities, which was concomitant with diminished contents of total phenolics, flavonoids and anthocyanins. Transcriptomic analysis revealed that GR24–0.1 treatment up-regulated the expression of genes associated with abscisic acid (ABA) biosynthesis and signal transduction, C-repeat binding factor (CBF) signaling pathway, anthocyanin synthesis and transport, antioxidant system, oxidative protein repair system as well as energy metabolism, contributing to the enhanced levels of some metabolites in these biochemical pathways. In contrast to GR24–0.1 treatment, reverse transcriptional and physiological effects in parallel with aggravated CI severity occurred in GR24–1.0 treated fruit, indicating a dosage-dependent regulatory effect of GR24 on litchi CI. The present findings provide insights into the potential mechanisms by which SLs regulate cold tolerance in postharvest litchi fruit.

Strigolactone-mediated amelioration of salinity stress in bread wheat: Insights from phytochemical and ion channels related genes expression analyses

Foliar application of growth regulators seems to alleviate the adverse effects of abiotic stresses in plants through different mechanisms such as antioxidative and gene expression regulation. As an important abiotic stress, salinity has an enormous negative impact on crop plants such as bread wheat. In the present study, exogenous strigolactone (GR24) was considered for its potential stress-mitigating effect in two contrasting wheats cultivars (‘Arta’ and ‘Karchia’) grown under 2,053,100 mM NaCl stress (10 dS m−1). Yield-related traits, oxidative (APX, POX, CAT, H2O2, MDA, GB and Proline), ionic indices (Na+ and K+ content in leaf and root), and the expression of a selected set of oxidative stress related genes (TaAPX, TaGPX, TaP5CS, TaNHX2, TaSOS1, TaHAK, TaAKT2 and TaHKT2;1) were surveyed in the flowering stage. Strigolactone application (10 μM) had a significant effect on the induction and improvement of biochemical and ionic features such as reducing the electrolyte leakage, H2O2 and MDA or increasing the grain yield, total protein, proline, GB and antioxidant enzymes (APX, POX) activity, of salinity-stressed plants. The gene expression analysis with real-time PCR showed transcriptional variation of selected genes in response to salt stress and GR24. Improved homeostasis in Na+ and K+ and their ratio was found to be correlated with the expression of the antiporter genes and the consequent reduction of ion toxicity. The findings of this study can improve our knowledge about complex mechanism of strigolactone plant hormone during salt stress in crop plans to mitigation of salinity stress.

Physiological and Transcriptome Analysis of the Effects of Exogenous Strigolactones on Drought Responses of Pepper Seedlings.

Drought stress significantly restricts the growth, yield, and quality of peppers. Strigolactone (SL), a relatively new plant hormone, has shown promise in alleviating drought-related symptoms in pepper plants. However, there is limited knowledge on how SL affects the gene expression in peppers when exposed to drought stress (DS) after the foliar application of SL. To explore this, we conducted a thorough physiological and transcriptome analysis investigation to uncover the mechanisms through which SL mitigates the effects of DS on pepper seedlings. DS inhibited the growth of pepper seedlings, altered antioxidant enzyme activity, reduced relative water content (RWC), and caused oxidative damage. On the contrary, the application of SL significantly enhanced RWC, promoted root morphology, and increased leaf pigment content. SL also protected pepper seedlings from drought-induced oxidative damage by reducing MDA and H2O2 levels and maintaining POD, CAT, and SOD activity. Moreover, transcriptomic analysis revealed that differentially expressed genes were enriched in ribosomes, ABC transporters, phenylpropanoid biosynthesis, and Auxin/MAPK signaling pathways in DS and DS + SL treatment. Furthermore, the results of qRT-PCR showed the up-regulation of AGR7, ABI5, BRI1, and PDR4 and down-regulation of SAPK6, NTF4, PYL6, and GPX4 in SL treatment compared with drought-only treatment. In particular, the key gene for SL signal transduction, SMXL6, was down-regulated under drought. These results elucidate the molecular aspects underlying SL-mediated plant DS tolerance, and provide pivotal strategies for effectively achieving pepper drought resilience.

Physiological and RNA-Seq Analyses on Exogenous Strigolactones Alleviating Drought by Improving Antioxidation and Photosynthesis in Wheat (Triticum aestivum L.).

Drought poses a significant challenge to global wheat production, and the application of exogenous phytohormones offers a convenient approach to enhancing drought tolerance of wheat. However, little is known about the molecular mechanism by which strigolactones (SLs), newly discovered phytohormones, alleviate drought stress in wheat. Therefore, this study is aimed at elucidating the physiological and molecular mechanisms operating in wheat and gaining insights into the specific role of SLs in ameliorating responses to the stress. The results showed that SLs application upregulated the expression of genes associated with the antioxidant defense system (Fe/Mn-SOD, PER1, PER22, SPC4, CAT2, APX1, APX7, GSTU6, GST4, GOR, GRXC1, and GRXC15), chlorophyll biogenesis (CHLH, and CPX), light-harvesting chlorophyll A-B binding proteins (WHAB1.6, and LHC Ib-21), electron transfer (PNSL2), E3 ubiquitin-protein ligase (BB, CHIP, and RHY1A), heat stress transcription factor (HSFA1, HSFA4D, and HSFC2B), heat shock proteins (HSP23.2, HSP16.9A, HSP17.9A, HSP21, HSP70, HSP70-16, HSP70-17, HSP70-8, HSP90-5, and HSP90-6), DnaJ family members (ATJ1, ATJ3, and DJA6), as well as other chaperones (BAG1, CIP73, CIPB1, and CPN60I). but the expression level of genes involved in chlorophyll degradation (SGR, NOL, PPH, PAO, TIC55, and PTC52) as well as photorespiration (AGT2) was found to be downregulated by SLs priming. As a result, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were enhanced, and chlorophyll content and photosynthetic rate were increased, which indicated the alleviation of drought stress in wheat. These findings demonstrated that SLs alleviate drought stress by promoting photosynthesis through enhancing chlorophyll levels, and by facilitating ROS scavenging through modulation of the antioxidant system. The study advances understandings of the molecular mechanism underlying SLs-mediated drought alleviation and provides valuable insights for implementing sustainable farming practice under water restriction.

Exogenous strigolactones alleviate drought stress in wheat (Triticum aestivum L.) by promoting cell wall biogenesis to optimize root architecture

Exogenous strigolactones (SLs, GR24) are widely used to alleviate drought stress in wheat. The physiological and biochemical mechanisms via which SLs help overcome drought stress in wheat shoots have been reported; however, the mechanisms in wheat roots are unclear. The present study explored the effects of the exogenous application of SLs on wheat roots’ growth and molecular responses under drought stress using physiological analysis and RNA-seq. RNA-seq of roots showed that SLs mainly upregulated signal transduction genes (SIS8, CBL3, GLR2.8, LRK10L-2.4, CRK29, and CRK8) and transcription factors genes (ABR1, BHLH61, and MYB93). Besides, SLs upregulated a few downstream target genes, including antioxidant genes (PER2, GSTF1, and GSTU6), cell wall biogenesis genes (SUS4, ADF3, UGT13248, UGT85A24, UGT709G2, BGLU31, and LAC5), an aquaporin-encoding gene (TIP4-3), and dehydrin-encoding genes (DHN2, DHN3, and DHN4). As a result, SLs reduced oxidative damage, optimized root architecture, improved leaf-water relation, and alleviated drought damage. Thus, the present study provides novel insights into GR24-mediated drought stress management and a scientific basis for proposing GR24 application.

Effect of strigolactone on growth, photosynthetic efficiency, antioxidant activity, and osmolytes accumulation in different maize (Zea mays L.) hybrids grown under drought stress

ABSTRACT Drought alters plant physiology, morphology, and biochemical pathways, necessitating effective mitigation strategies. Strigolactones (SLs) are phytohormones known to enhance plant growth under abiotic stress. However, their specific impact on drought stress in maize remains unclear. This study aimed to determine the optimal SL concentration for mitigating drought stress in two maize hybrids (HY-1898, FH-1046). Maize plants were subjected to 60% field capacity drought stress in a pot experiment. After 40 d, different concentrations (0, 0.001, 0.01, and 0.1 mg L−1) of the synthetic SL analogue GR24 were applied to evaluate their effects on growth features, photosynthesis attributes, and osmolyte accumulation in the maize hybrids. Results showed that exogenous SL application significantly increased photosynthetic pigments in maize hybrids under drought stress. Chlorophyll content, gas exchange characteristics, net CO2 assimilation rate, stomatal conductance, water use efficiency, and antioxidant activities were enhanced by GR24. Leaf ascorbic acid and total phenolics also increased with SL application. Organic osmolytes, such as glycine betaine and free proline, were elevated in both maize hybrids under drought stress. Yield-related parameters, including cob diameter, cob weight, number of seeds per cob, and number of seeds per plant, were significantly increased by GR24 under drought stress. Our findings highlight the potential of GR24 foliar application to mitigate drought stress and promote maize growth and grain yield in a concentration-dependent manner. The minimum effective SL concentration against drought stress was determined to be 0.01 mg L−1. Overall, foliar application of GR24 could serve as a sustainable approach for drought tolerance in agriculture.

Strigolactones modulate cotton fiber elongation and secondary cell wall thickening

Cotton is one of the most important economic crops in the world, and it is a major source of fiber in the textile industry. Strigolactones (SLs) are a class of carotenoid-derived plant hormones involved in many processes of plant growth and development, although the functions of SL in fiber development remain largely unknown. Here, we found that the endogenous SLs were significantly higher in fibers at 20 days post-anthesis (DPA). Exogenous SLs significantly increased fiber length and cell wall thickness. Furthermore, we cloned three key SL biosynthetic genes, namely GhD27, GhMAX3, and GhMAX4, which were highly expressed in fibers, and subcellular localization analyses revealed that GhD27, GhMAX3, and GhMAX4 were localized in the chloroplast. The exogenous expression of GhD27, GhMAX3, and GhMAX4 complemented the physiological phenotypes of d27, max3, and max4 mutations in Arabidopsis, respectively. Knockdown of GhD27, GhMAX3, and GhMAX4 in cotton resulted in increased numbers of axillary buds and leaves, reduced fiber length, and significantly reduced fiber thickness. These findings revealed that SLs participate in plant growth, fiber elongation, and secondary cell wall formation in cotton. These results provide new and effective genetic resources for improving cotton fiber yield and plant architecture.

Effects of exogenous strigolactone on growth, dry matter accumulation, and yield of tissue-cultured ginger

ABSTRACT Ginger tissue culture seedlings can reduce the incidence of soil-borne diseases. However, they have several branches, small ginger bulbs, and slow seed recovery. Strigolactone can inhibit the growth of lateral buds, adjust plant types, and increase crop yield. This study used exogenous strigolactone to treat tissue-cultured ginger and assess its effects on growth, dry matter accumulation, and yield. The results showed that the number of branches and ginger bulbs per plant decreased significantly with the application of exogenous GR24 (Synthetic analog of strigolactone, rac-GR24), and higher concentrations led to a greater decrease. Plant height, stem diameter, root, rhizome, stem sheath, leaf and plant dry matter accumulation, average ginger bulb weight, and yield increased significantly, increasing initially and then decreasing with increasing concentration. Depending on the concentrations, exogenous strigolactone can inhibit the branching of tissue-cultured ginger, reduce the number of branches, increase plant height and stem diameter, optimize the aboveground plant type, increase dry matter accumulation and root-shoot ratio, decrease the number of ginger bulbs per plant, increase the average ginger ball weight, and increase yield. When the GR24 concentration was further increased, the number of branches, the plant height, stem diameter, dry matter accumulation, root shoot ratio, ginger bulbs per plant, average weight of ginger bulbs, and ginger yield decreased. Treatment with 7.5 um L−1 of exogenous GR24 could optimize the plant type of tissue-cultured ginger and increase yield.

The Yield and Quality Formation of Wheat Induced by Exogenous Strigolactones in Drought Condition

Drought is one of the major disasters affecting wheat. The change of wheat yield and quality directly affects the global population diet health. In this study, Strigolactones (SL) were sprayed on the leaf surface to study the relationship between wheat photosynthesis, nitrogen transport and yield and quality formation, further clarifying the influence of Sl on the synergic formation of yield and quality. The results showed that Sl could promote the accumulation of photosynthetic pigments in leaves, reduce nitrogen content in aging leaves and improve nitrogen transport level, then promote the improvement of grain yield and quality, so as to provide a reference for the application of Sl in wheat stress-resistant cultivation.

Combined analyses of transcriptome and metabolome reveal the mechanism of exogenous strigolactone regulating the response of elephant grass to drought stress.

Elephant grass is widely used in feed production and ecological restoration because of its huge biomass and low occurrence of diseases and insect pets. However, drought seriously affects growth and development of this grass. Strigolactone (SL), a small molecular phytohormone, reportedly participates in improving resilience to cope with arid environment. But the mechanism of SL regulating elephant grass to response to drought stress remains unknown and needs further investigation. We conducted RNA-seq experiments and identified 84,296 genes including 765 and 2325 upregulated differential expression genes (DEGs) and 622 and 1826 downregulated DEGs, compared drought rehydration with spraying SL in roots and leaves, respectively. Combined with targeted phytohormones metabolite analysis, five hormones including 6-BA, ABA, MeSA, NAA, and JA had significant changes under re-watering and spraying SL stages. Moreover, a total of 17 co-expression modules were identified, of which eight modules had the most significant correlation with all physiological indicators with weighted gene co-expression network analysis. The venn analysis revealed the common genes between Kyoto Encyclopedia of Genes and Genomes enriched functional DEGs and the top 30 hub genes of higher weights in eight modules, respectively. Finally, 44 DEGs had been identified as key genes which played a major role in SL response to drought stress. After verification of its expression level by qPCR, six key genes in elephant grass including PpPEPCK, PpRuBPC, PpPGK, PpGAPDH, PpFBA, and PpSBPase genes regulated photosynthetic capacity under the SL treatment to respond to drought stress. Meanwhile, PpACAT, PpMFP2, PpAGT2, PpIVD, PpMCCA, and PpMCCB regulated root development and phytohormone crosstalk to respond to water deficit conditions. Our research led to a more comprehensive understanding about exogenous SL that plays a role in elephant grass response to drought stress and revealed insights into the SL regulating molecular mechanism in plants to adapt to the arid environment.

The Attraction of Apple Rhizosphere Microorganisms and Changing Leaf Characteristics by Strigolactone

Apple leaf characteristics are the most important vegetative growth and development traits. The apple rhizosphere is also indirectly responsible for apple growth and development. It provides roots with elements and compounds that improve roots’ and shoots’ growth and development. The application of exogenous plant growth regulators such as strigolactones (SLs) has become one of the main trends for improving vegetative growth and enhancing the rhizosphere microbiome. This study aimed to investigate the effect of the exogenous SLs on some leaf characteristics, such as leaf area, angle, nitrogen content, chlorophyll content, and apical area diameter, in addition to the composition of the rhizosphere microbiome of apple M9 rootstock. The apple rootstocks were treated with various concentrations of GR24, an analog of SLs; the concentrations were 0, 1, 5, and 10 µM. The study found that the treatments of 5 µM increased the leaf–stem angles and leaf length while decreasing the apical diameter. The treatments of 1 and 5 µM increased leaf nitrogen content; however, this effect was not observed when using the higher concentration of 10 µM. The lower concentration (1 µM) led to a different abundance and diversity of microorganisms compared to the higher concentration (10 µm).

Insights into strigolactone (GR24) mediated regulation of cadmium-induced changes and ROS metabolism in Artemisia annua

Agricultural soil contamination and subsequently crops still require alternative solutions to reduce associated environmental risks. The effects of strigolactones (SLs) in alleviating cadmium (Cd) phytotoxicity in Artemisia annua plants were investigated during this study. Strigolactones play a vital role during plant growth and development due to their complex interplay during a plethora of biochemical processes. However, information on the potential of SLs to elicit abiotic stress signaling and trigger physiological modifications in plants is limited. In order to decipher the same, A. annua plants were exposed to different concentrations of Cd (20 and 40 mg kg-1), with or without the supplementation of exogenous SL (GR24, a SL analogue) at 4 µM concentration. Under Cd stress, excess Cd accumulation resulted in reduced growth, physio-biochemical traits, and artemisinin content. However, the follow-up treatment of GR24 maintained a steady state equilibrium between reactive oxygen species and antioxidant enzymes, improved chlorophyll fluorescence parameters such as Fv/Fm, ФPSII, and ETR for improved photosynthesis, enhanced chlorophyll content, maintained chloroplast ultrastructure, improved the glandular trichome (GT) attributes and artemisinin production in A. annua. Moreover, it also resulted in improved membrane stability, reduced Cd accumulation, and regulated the behaviour of stomatal apertures for better stomatal conductance under Cd stress. The results of our study suggest that GR24 could be highly effective in alleviating Cd-induced damages in A. annua. It acts via the modulation of the antioxidant enzyme system for redox homeostasis, protection of the chloroplasts and pigments for improved photosynthetic performance, and improved GT attributes for enhanced artemisinin production in A. annua.