Search Results (12)

Strigolactones (SLs), a novel class of plant hormones, play a crucial role in plant growth and development. SMXL (SUPPRESSOR OF MAX2 1-like) is a key gene in the SL signaling pathway, regulating its function by inhibiting the reception of SL signals. Therefore, investigating how SMXL regulates SL to influence wheat growth, development, and stress resistance is of significant importance. In this study, 22 SMXL genes were identified in the Chinese Spring wheat reference genome. Bioinformatics analysis revealed that these genes belong to the Group II subfamily, exhibiting similar physicochemical properties and conserved motifs. Ka/Ks analysis indicated that these genes have undergone purifying selection during evolution. Cis-acting element analysis showed that the promoter regions of TaSMXL genes are enriched with light-responsive elements and regulatory elements related to growth, development, and stress responses. Expression pattern analysis demonstrated that TaSMXL genes exhibit significant differential expression under drought, salt, and cold stress conditions, revealing the potential molecular mechanisms of wheat’s response to multiple abiotic stresses. This study provides a theoretical foundation for understanding the functional roles of SMXL genes in wheat and offers valuable candidate gene resources for breeding stress-resistant wheat varieties. Full article

The novel plant hormone strigolactones (SL) are involved significantly in plant growth and development. Its key members SMXL6, 7, 8 can modulate SL signal reception and response negatively and can regulate plant branching remarkably. There are relatively scarce studies of cotton SMXL gene family, and this study was carried out to clarify the role of GbSMXL8 in cotton fiber development. Phylogenetic analysis identified 48 cotton SMXL genes, which were divided into SMXL-I (SMXL 1, 2), SMXL-II (SMXL 3) and SMXL-III (SMXL6, 7, 8) groups. The results of the cis-element analysis indicated that the SMXL gene could respond to hormones and the environment to modulate cotton growth process. A candidate gene GbSMXL8 was screened out based on the expression difference in extreme varieties of Gossypium barbadense. Tissue-specific analysis indicated that GbSMXL8 was mainly expressed in roots, 20D, 25D, and 35D and was involved in SL signaling pathways. In vitro ovule culture experiments showed that exogenous SLs (GR24) could promote the fiber elongation of G. barbadense, and GbSMXL8 expression was increased after GR24 treatment, indicating that GbSMXL8 was specifically responsive to GR24 in regulating fiber growth. GbSMXL8 knockout resulted in creased length and number of epidermal hairs and the length of fiber, indicating the interference role of GbSMXL8 gene with the development of cotton fiber. The GbSMXL8 transgenic plant was detected with a higher chlorophyll content and photosynthetic rate than those of the control plant, producing a direct impact on plant growth, yield, and biomass accumulation. GbSMXL8 gene knockout could increase plant height, accelerate growth rate, and lengthen fiber length. Intervening GbSMXL8 may mediate cotton growth, plant type formation and fiber elongation. In conclusion, the present study uncovers the function of GbSMXL8-mediated SL signal in cotton, providing theoretical insight for future breeding of new cotton varieties. Full article

SUPPRESSOR OF MAX2 1-LIKE (SMXL) proteins are negative regulators of strigolactone (SL) signal transduction that play an important role in regulating plant branching and responses to abiotic stress. Here, we studied the role of SMXL proteins in pear growth, development, and stress resistance. A total of 18 SMXL members were characterized in ‘duli’. All SMXL members were localized to chloroplasts. Chromosome mapping analysis showed that the members of this family were unevenly distributed on 14 chromosomes. Gene fragment replication analysis showed that there were no tandem repeat genes in PbSMXLs, and 12 pairs of homologous genes were fragment duplications. There were 30 pairs of homologous genes between ‘duli’ and apples, and 17 between ‘duli’ and Arabidopsis thaliana. Analysis of cis-acting elements showed that there was a large number of photo-effector elements, short-effector elements, hormone-responsive elements, and abiotic stress-responsive elements in the promoter sequences of this family. Analysis of enzyme activity and endogenous SL showed that β-carotenoid isomerase (D27), carotenoid cleavage dioxygenase 7 (CCD7), lateral branch oxidoreductase (LBO) levels, and SL content were higher in ‘duli’ roots and leaves compared in the control under exogenous GA₃ (gibberellin 3), IAA (indole-3-acetic acid), GR24 (synthetic SL analog), and NaCl. Most SMXL genes in ‘duli’ were highly expressed in branches and axillary lobes, but their expression was low in fruits. qRT-PCR analysis revealed that eight PbSMXL genes were responsive to GA₃, PAC (Paclobutrazol), IAA, ABA (abscisic acid), GR24, and Tis108 (SL biosynthesis inhibitor). PbSMXLs responded positively to salt stress. The expression of PbSMXL6 and PbSMXL15 was significantly induced under salt stress. The expression of PbSMXL7, PbSMXL10, and PbSMXL15 was significantly induced by Tis108 treatment. The results of this study enhance our understanding of the role of SMXL genes in the responses to plant growth regulators and salt stress. Our findings will also aid future studies of the functions of SMXL genes in ‘duli’. Full article

The development of branching plays a pivotal role in the cultivation of ornamental chrysanthemums, as it dictates the ultimate morphology and quality of the plants. Strigolactones (SLs) are associated with apical dominance to indirectly inhibit shoot branching. Chrysanthemum morifolium ‘Baltasar’ in this study was subjected to treatment with three hormones: auxin (IAA), 6-BA, and GR24. Following the exogenous application of GR24 and IAA, a significant reduction in both the length and quantity of lateral buds on chrysanthemums was observed. Additionally, there was a notable down-regulation in the expression levels of CmPIN1 (associated with auxin transport) and CmIPT3, which is involved in cytokinin (CK) synthesis. After the application of 6-BA, there was a significant increase in both the length and quantity of lateral buds on chrysanthemums. Subsequently, the separate application of IAA and 6-BA to C. morifolium ‘Baltasar’ notably induced the expression of CmMAX1, a gene involved in the biosynthesis of strigolactones, and CmSMXL6, a gene associated with the signaling pathway of SLs, suggesting a negative regulatory role for SLs and auxin in chrysanthemum lateral buds, while CK demonstrated positive regulation. Cloning and expression analysis of CmSMXL6, a member of the D53/SMXL gene family in chrysanthemum, revealed its up-regulation following GR24 treatment, peaking at 9 h. The overexpression of CmSMXL6 in Arabidopsis thaliana promoted increased numbers of primary and secondary branches. In transgenic lines, genes associated with SLs synthesis (AtMAX1, AtMAX2, and AtMAX3) exhibited varying degrees of down-regulation, while the branching-inhibitory gene AtBRC1 also displayed decreased expression levels. These findings suggest that CmSMXL6 plays a role in promoting branching. Full article

SMXL genes constitute a conserved gene family that is ubiquitous in angiosperms and involved in regulating various plant processes, including branching, leaf elongation, and anthocyanin biosynthesis, but little is known about their molecular functions in pear branching. Here, we performed genome-wide identification and investigation of the SMXL genes in 16 angiosperms and analyzed their phylogenetics, structural features, conserved motifs, and expression patterns. In total, 121 SMXLs genes were identified and were classified into four groups. The number of non-redundant SMXL genes in each species varied from 3 (Amborella trichopoda Baill.) to 18 (Glycine max Merr.) and revealed clear gene expansion events over evolutionary history. All the SMXL genes showed conserved structures, containing no more than two introns. Three-dimensional protein structure prediction revealed distinct structures between but similar structures within groups. A quantitative real-time PCR analysis revealed different expressions of 10 SMXL genes from pear branching induced by fruit-thinning treatment. Overall, our study provides a comprehensive investigation of SMXL genes in the Rosaceae family, especially pear. The results offer a reference for understanding the evolutionary history of SMXL genes and provide excellent candidates for studying fruit tree branching regulation, and in facilitating pear pruning and planting strategies. Full article

Petioles of non-heading Chinese cabbage are not only an important edible part but also a conduit for nutrient transport, holding significant agricultural and research value. In this study, we conducted a comprehensive genetic analysis of petiole-related traits using a segregating population. Modern quantitative genetic approaches were applied to investigate the genetic regulation of petiole thickness. The results indicated that petiole thickness is a quantitative trait, and the identified genetic model was consistent with two pairs of additive-dominant main genes and additive-dominant polygenes (2MG-AD). BSA-seq analysis identified a major effect of QTL controlling petiole thickness on chromosome A09: 42.08–45.09 Mb, spanning 3.01 Mb, designated as QTL-BrLH9. Utilizing InDel markers, the interval was narrowed down to 51 kb, encompassing 14 genes with annotations for 10 of them. Within the interval, four mutated genes were detected. Combined with gene annotation, protein sequence analysis, and homology alignment, it was found that BraA09g063520.3C’s homologous gene SMXL6 in Arabidopsis (Arabidopsis thaliana (L.) Heynh) is an inhibitor of the coding and synthesis of the strigolactone pathway. Strigolactone (SLs) plays an important role in plant growth and development. The cloning results showed that multiple frameshift mutations and non-synonymous mutations occurred on the exon. The qPCR results showed that the expression of the gene was significantly different between the two parents at the adult stage, so it was speculated that it would lead to changes in petiole thickness. BraA09g063520.3C was predicted as the final candidate gene. Full article

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. Full article

SUPPRESSOR OF MAX2-LIKE 6, 7, and 8 (SMXL6,7,8) function as repressors and transcription factors of the strigolactone (SL) signaling pathway, playing an important role in the development and stress tolerance in Arabidopsis thaliana. However, the molecular mechanism by which SMXL6,7,8 negatively regulate drought tolerance and ABA response remains largely unexplored. In the present study, the interacting protein and downstream target genes of SMXL6,7,8 were investigated. Our results showed that the substrate receptor for the CUL4-based E3 ligase DDB1-BINDING WD-REPEAT DOMAIN (DWD) HYPERSENSITIVE TO ABA DEFICIENT 1 (ABA1) (DWA1) physically interacted with SMXL6,7,8. The degradation of SMXL6,7,8 proteins were partially dependent on DWA1. Disruption of SMXL6,7,8 resulted in increased drought tolerance and could restore the drought-sensitive phenotype of the dwa1 mutant. In addition, SMXL6,7,8 could directly bind to the promoter of SUCROSE NONFERMENTING 1 (SNF1)-RELATED PROTEIN KINASE 2.3 (SnRK2.3) to repress its transcription. The mutations in SnRK2.2/2.3 significantly suppressed the hypersensitivity of smxl6/7/8 to ABA-mediated inhibition of seed germination. Conclusively, SMXL6,7,8 interact with DWA1 to negatively regulate drought tolerance and target ABA-response genes. These data provide insights into drought tolerance and ABA response in Arabidopsis via the SMXL6,7,8-mediated SL signaling pathway. Full article

Strigolactones (SLs), a new class of plant hormones, are implicated in the regulation of various biological processes. However, the related family members and functions are not identified in longan (Dimocarpus longan Lour.). In this study, 23 genes in the CCD, D27, and SMXL family were identified in the longan genome. The phylogenetic relationships, gene structure, conserved motifs, promoter elements, and transcription factor-binding site predictions were comprehensively analysed. The expression profiles indicated that these genes may play important roles in longan organ development and abiotic stress responses, especially during early somatic embryogenesis (SE). Furthermore, GR24 (synthetic SL analogue) and Tis108 (SL biosynthesis inhibitor) could affect longan early SE by regulating the levels of endogenous IAA (indole-3-acetic acid), JA (jasmonic acid), GA (gibberellin), and ABA (abscisic acid). Overexpression of SMXL6 resulted in inhibition of longan SE by regulating the synthesis of SLs, carotenoids, and IAA levels. This study establishes a foundation for further investigation of SL genes and provides novel insights into their biological functions. Full article

SMXL6,7,8 are important target proteins in strigolactone (SL) signal pathway, which negatively regulate the reception and response of SL signal, and play an important role in regulating plant branching. However, there is a relative lack of research on soybean SMXL gene family. In this study, 31 soybean SMXL genes were identified by phylogenetic analysis and divided into three groups. Based on the analysis of GmSMXL gene’s structure and motif composition, it was found that the GmSMXL members in the same group were similar. The results of cis-element analysis showed that GmSMXL genes may regulate the growth and development of soybean by responding to hormones and environment. Based on the tissue specificity analysis and GR24 treatment, the results showed that four GmSMXLs in G1 group were predominantly expressed in stems, axillary buds and leaves and involved in SL signal pathway. Finally, under shading stress, the expression of four genes in G1 group was slightly different in different varieties, which may be the reason for the difference in branching ability of different varieties under shading stress. We have systematically studied the SMXL gene family in soybean, which may lay a foundation for the study of the function of GmSMXL gene in the future. Full article

Mexiletine (MXL) is a class IB antiarrhythmic agent, acting as a non-selective voltage-gated sodium channel blocker, used in therapy as a racemic mixture R,S-MXL hydrochloride. The aim of the current study was the development of a new, fast, and efficient method for the chiral separation of MXL enantiomers using capillary electrophoresis (CE) and cyclodextrins (CDs) as chiral selectors (CSs). After an initial CS screening, using several neutral and charged CDs, at four pH levels, heptakis-2,3,6-tri-O-methyl-β-CD (TM-β-CD), a neutral derivatized CD, was chosen as the optimum CS for the enantioseparation. For method optimization, an initial screening fractional factorial design was applied to identify the most significant parameters, followed by a face-centered central composite design to establish the optimal separation conditions. The best results were obtained by applying the following optimized electrophoretic conditions: 60 mM phosphate buffer, pH 5.0, 50 mM TM-β-CD, temperature 20 °C, applied voltage 30 kV, hydrodynamic injection 50 mbar/s. MXL enantiomers were baseline separated with a resolution of 1.52 during a migration time of under 5 min; S-MXL was the first migrating enantiomer. The method’s analytical performance was verified in terms of precision, linearity, accuracy, and robustness (applying a Plackett–Burman design). The developed method was applied for the determination of MXL enantiomers in pharmaceuticals. A computer modeling of the MXL-CD complexes was applied to characterize host–guest chiral recognition. Full article

Previous investigations have shown that the SUPPRESSORS OF MAX2 1-LIKE6, 7 and 8 (SMXL6, 7 and 8) proteins redundantly repress strigolactone (SL) signaling in plant growth and development. Recently, a growing body of evidence indicated that SLs positively regulate plant drought resistance through functional analyses of genes involved in SL biosynthesis and positive regulation of SL signaling. However, the functions of the SL-signaling negative regulators SMXL6, 7 and 8 in drought resistance and the associated mechanisms remain elusive. To reveal the functions of these SMXL proteins, we analyzed the drought-resistant phenotype of the triple smxl6,7,8 mutant plants and studied several drought resistance-related traits. Our results showed that the smxl6,7,8 mutant plants were more resistant to drought than wild-type plants. Physiological investigations indicated that the smxl6,7,8 mutant plants exhibited higher leaf surface temperature, reduced cuticle permeability, as well as decreases in drought-induced water loss and cell membrane damage in comparison with wild-type plants. Additionally, smxl6,7,8 mutant plants displayed an increase in anthocyanin biosynthesis during drought, enhanced detoxification capacity and increased sensitivity to abscisic acid in cotyledon opening and growth inhibition assays. A good correlation between the expression levels of some relevant genes and the examined physiological and biochemical traits was observed. Our findings together indicate that the SMXL6, 7 and 8 act as negative regulators of drought resistance, and that disruption of these SMXL genes in crops may provide a novel way to improve their drought resistance. Full article