Comprehensive insights into the impact of bacterial indole-3-acetic acid on sensory preferences in Drosophila melanogaster.

Several bacteria of environmental and clinical origins, including some human-associated strains secrete a cross-kingdom signaling molecule indole-3-acetic acid (IAA). IAA is a tryptophan (trp) derivative mainly known for regulating plant growth and development as a hormone. However, the nutritional sources that boost IAA secretion in bacteria and the impact of secreted IAA on non-plant eukaryotic hosts remained less explored. Here, we demonstrate significant trp-dependent IAA production in Pseudomonas juntendi NEEL19 when provided with ethanol as a carbon source in liquid cultures. IAA was further characterized to modulate the odor discrimination, motility and survivability in Drosophila melanogaster. A detailed analysis of IAA-fed fly brain proteome using high-resolution mass spectrometry showed significant (fold change, ± 2; p ≤ 0.05) alteration in the proteins governing neuromuscular features, audio-visual perception and energy metabolism as compared to IAA-unfed controls. Sex-wise variations in differentially regulated proteins were witnessed despite having similar visible changes in chemo perception and psychomotor responses in IAA-fed flies. This study not only revealed ethanol-specific enhancement in trp-dependent IAA production in P. juntendi, but also showed marked behavioral alterations in flies for which variations in an array of proteins governing odor discrimination, psychomotor responses, and energy metabolism are held responsible. Our study provided novel insights into disruptive attributes of bacterial IAA that can potentially influence the eukaryotic gut-brain axis having broad environmental and clinical implications.

Ethylene controls three-dimensional growth involving reduced auxin levels in the moss Physcomitrium patens.

The conquest of land by plants was concomitant with, and possibly enabled by, the evolution of three-dimensional (3D) growth. The moss Physcomitrium patens provides a model system for elucidating molecular mechanisms in the initiation of 3D growth. Here, we investigate whether the phytohormone ethylene, which is believed to have been a signal before land plant emergence, plays a role in 3D growth regulation in P. patens. We report ethylene controls 3D gametophore formation, based on results from exogenously applied ethylene and genetic manipulation of PpEIN2, which is a central component in the ethylene signaling pathway. Overexpression (OE) of PpEIN2 activates ethylene responses and leads to earlier formation of gametophores with fewer gametophores produced thereafter, phenocopying ethylene-treated wild-type. Conversely, Ppein2 knockout mutants, which are ethylene insensitive, show initially delayed gametophore formation with more gametophores produced later. Furthermore, pharmacological and biochemical analyses reveal auxin levels are decreased in the OE lines but increased in the knockout mutants. Our results suggest that evolutionarily, ethylene and auxin molecular networks were recruited to build the plant body plan in ancestral land plants. This might have played a role in enabling ancient plants to acclimate to the continental surfaces of the planet.

Cotton sphingosine kinase GhLCBK1 participates in fiber cell elongation by affecting sphingosine-1-phophate and auxin synthesis.

Sphingolipids serve as essential components of biomembrane and possess significant bioactive properties. Sphingosine-1-phophate (S1P) plays a key role in plant resistance to stress, but its specific impact on plant growth and development remains to be fully elucidated. Cotton fiber cells are an ideal material for investigating the growth and maturation of plant cells. In this study, we examined the content and composition of sphingosine (Sph) and S1P throughout the progression of fiber cell development. The content of S1P elevated gradually during fiber elongation but declined during the transition stage. Exogenous application of S1P promoted fiber elongation while using of FTY720 (an antagonist of S1P), and DMS (an inhibitor of LCBK) hindered fiber elongation. Cotton Long Chain Base Kinase 1 (GhLCBK1) was notably expressed during the fiber elongation stage, containing all conserved domains of LCBK protein and localized in the endoplasmic reticulum. Overexpression GhLCBK1 increased the S1P content and promoted fiber elongation while retarded secondary cell wall (SCW) deposition. Conversely, downregulation of GhLCBK1 reduced the S1P levels, and suppressed fiber elongation, and accelerated SCW deposition. Transcriptome analysis revealed that upregulating GhLCBK1 or applying S1P induced the expression of GhEXPANSIN and auxin related genes. Furthermore, the levels of IAA were elevated and reduced in the fibers when up-regulating or down-regulating GhLCBK1, respectively. Our investigation demonstrated that GhLCBK1 and its product S1P facilitated the elongation of fiber cells by affecting auxin biosynthesis. This study contributes novel insights into the intricate regulatory pathways involved in fiber cell elongation, identifying GhLCBK1 as a potential target gene and laying the groundwork for enhancing fiber quality via genetic manipulation.

The activation of Arabidopsis axillary buds involves a switch from slow to rapid committed outgrowth regulated by auxin and strigolactone.

Arabidopsis thaliana (Arabidopsis) shoot architecture is largely determined by the pattern of axillary buds that grow into lateral branches, the regulation of which requires integrating both local and systemic signals. Nodal explants - stem explants each bearing one leaf and its associated axillary bud - are a simplified system to understand the regulation of bud activation. To explore signal integration in bud activation, we characterised the growth dynamics of buds in nodal explants in key mutants and under different treatments. We observed that isolated axillary buds activate in two genetically and physiologically separable phases: a slow-growing lag phase, followed by a switch to rapid outgrowth. Modifying BRANCHED1 expression or the properties of the auxin transport network, including via strigolactone application, changed the length of the lag phase. While most interventions affected only the length of the lag phase, strigolactone treatment and a second bud also affected the rapid growth phase. Our results are consistent with the hypothesis that the slow-growing lag phase corresponds to the time during which buds establish canalised auxin transport out of the bud, after which they enter a rapid growth phase. Our work also hints at a role for auxin transport in influencing the maximum growth rate of branches.

Wounding-Related Signaling Is Integrated within the Auxin-Response Framework to Induce Adventitious Rooting in Chestnut.

Wounding and exogenous auxin are needed to induce adventitious roots in chestnut microshoots. However, the specific inductive role of wounding has not been characterized in this species. In the present work, two main goals were established: First, we prompted to optimize exogenous auxin treatments to improve the overall health status of the shoots at the end of the rooting cycle. Second, we developed a time-series transcriptomic analysis to compare gene expression in response to wounding alone and wounding plus auxin, focusing on the early events within the first days after treatments. Results suggest that the expression of many genes involved in the rooting process is under direct or indirect control of both stimuli. However, specific levels of expression of relevant genes are only attained when both treatments are applied simultaneously, leading to the successful development of roots. In this sense, we have identified four transcription factors upregulated by auxin (CsLBD16, CsERF113, Cs22D and CsIAA6), with some of them also being induced by wounding. The highest expression levels of these genes occurred when wounding and auxin treatments were applied simultaneously, correlating with the rooting response of the shoots. The results of this work clarify the genetic nature of the wounding response in chestnut, its relation to adventitious rooting, and might be helpful in the development of more specific protocols for the vegetative propagation of this species.

Integrated Transcriptomic and Metabolomic Analysis of Exogenous NAA Effects on Maize Seedling Root Systems under Potassium Deficiency.

Auxin plays a crucial role in regulating root growth and development, and its distribution pattern under environmental stimuli significantly influences root plasticity. Under K deficiency, the interaction between K+ transporters and auxin can modulate root development. This study compared the differences in root morphology and physiological mechanisms of the low-K-tolerant maize inbred line 90-21-3 and K-sensitive maize inbred line D937 under K-deficiency (K+ = 0.2 mM) with exogenous NAA (1-naphthaleneacetic acid, NAA = 0.01 mM) treatment. Root systems of 90-21-3 exhibited higher K+ absorption efficiency. Conversely, D937 seedling roots demonstrated greater plasticity and higher K+ content. In-depth analysis through transcriptomics and metabolomics revealed that 90-21-3 and D937 seedling roots showed differential responses to exogenous NAA under K-deficiency. In 90-21-3, upregulation of the expression of K+ absorption and transport-related proteins (proton-exporting ATPase and potassium transporter) and the enrichment of antioxidant-related functional genes were observed. In D937, exogenous NAA promoted the responses of genes related to intercellular ethylene and cation transport to K-deficiency. Differential metabolite enrichment analysis primarily revealed significant enrichment in flavonoid biosynthesis, tryptophan metabolism, and hormone signaling pathways. Integrated transcriptomic and metabolomic analyses revealed that phenylpropanoid biosynthesis is a crucial pathway, with core genes (related to peroxidase enzyme) and core metabolites upregulated in 90-21-3. The findings suggest that under K-deficiency, exogenous NAA induces substantial changes in maize roots, with the phenylpropanoid biosynthesis pathway playing a crucial role in the maize root's response to exogenous NAA regulation under K-deficiency.

Analysis of the regulatory mechanism of exogenous IAA-mediated tryptophan accumulation and synthesis of endogenous IAA in Chlorococcum humicola.

The activated sludge method is widely used for the treatment of phenol-containing wastewater, which gives rise to the problem of toxic residual sludge accumulation. Indole-3-acetic acid (IAA), a typical phytohormone, facilitates the microalgal resistance to toxic inhibition while promoting biomass accumulation. In this study, Chlorococcum humicola (C. humicola) was cultured in toxic sludge extract and different concentrations of IAA were used to regulate its physiological properties and enrichment of high value-added products. Ultimately, proteomics analysis was used to reveal the response mechanism of C. humicola to exogenous IAA. The results showed that the IAA concentration of 5 × 10-6 mol/L (M) was most beneficial for C. humicola to cope with the toxic stress in the sludge extract medium, to promote the activity of rubisco enzyme, to enhance the efficiency of photosynthesis, and, finally, to accumulate protein as a percentage of specific dry weight 1.57 times more than that of the control group. Exogenous IAA altered the relative abundance of various amino acids in C. humicola cells, and proteomic analyses showed that exogenous IAA stimulated the algal cells to produce more indole-3-glycerol phosphate (IGP), indole, and serine by up-regulating the enzymes. These precursors are converted to tryptophan under the regulation of tryptophan synthase (A0A383V983), and tryptophan can be metabolized to endogenous IAA to promote the growth of C. humicola. These findings have important implications for the treatment of toxic residual sludge while enriching for high-value amino acids.

Effect of gibberellin on crown root development in the mutant of the rice plasmodesmal Germin-like protein OsGER4.

Rice is an essential but highly stress-susceptible crop, whose root system plays an important role in plant development and stress adaptation. The rice root system architecture is controlled by gene regulatory networks involving different phytohormones including auxin, jasmonate, and gibberellin. Gibberellin is generally known as a molecular clock that interacts with different pathways to regulate root meristem development. The exogenous treatment of rice plantlets with Gibberellin reduced the number of crown roots, whilst the exogenous jasmonic acid treatment enhanced them by involving a Germin-like protein OsGER4. Due to those opposite effects, this study aims to investigate the effect of Gibberellin on crown root development in the rice mutant of the plasmodesmal Germin-like protein OsGER4. Under exogenous gibberellin treatment, the number of crown roots significantly increased in osger4 mutant lines and decreased in the OsGER4 overexpressed lines. GUS staining showed that OsGER4 was strongly expressed in rice root systems, particularly crown and lateral roots under GA3 application. Specifically, OsGER4 was strongly expressed from the exodermis, epidermis, sclerenchyma to the endodermis layers of the crown root, along the vascular bundle and throughout LR primordia. The plasmodesmal protein OsGER4 is suggested to be involved in crown root development by maintaining hormone homeostasis, including Gibberillin.

Above and belowground phenotypic response to exogenous auxin across Arabidopsis thaliana mutants and natural accessions varies from seedling to reproductive maturity.

Background: Plant hormones influence phenology, development, and function of above and belowground plant structures. In seedlings, auxin influences the initiation and development of lateral roots and root systems. How auxin-related genes influence root initiation at early life stages has been investigated from numerous perspectives. There is a gap in our understanding of how these genes influence root size through the life cycle and in mature plants. Across development, the influence of a particular gene on plant phenotypes is partly regulated by the addition of a poly-A tail to mRNA transcripts via alternative polyadenylation (APA). Auxin related genes have documented variation in APA, with auxin itself contributing to APA site switches. Studies of the influence of exogenous auxin on natural plant accessions and mutants of auxin pathway gene families exhibiting variation in APA are required for a more complete understanding of genotype by development by hormone interactions in whole plant and fitness traits. Methods: We studied Arabidopsis thaliana homozygous mutant lines with inserts in auxin-related genes previously identified to exhibit variation in number of APA sites. Our growth chamber experiment included wildtype Col-0 controls, mutant lines, and natural accession phytometers. We applied exogenous auxin through the life cycle. We quantified belowground and aboveground phenotypes in 14 day old, 21 day old seedlings and plants at reproductive maturity. We contrasted root, rosette and flowering phenotypes across wildtype, auxin mutant, and natural accession lines, APA groups, hormone treatments, and life stages using general linear models. Results: The root systems and rosettes of mutant lines in auxin related genes varied in response to auxin applications across life stages and varied between genotypes within life stages. In seedlings, exposure to auxin decreased size, but increased lateral root density, whereas at reproductive maturity, plants displayed greater aboveground mass and total root length. These differences may in part be due to a shift which delayed the reproductive stage when plants were treated with auxin. Root traits of auxin related mutants depended on the number of APA sites of mutant genes and the plant's developmental stage. Mutants with inserts in genes with many APA sites exhibited lower early seedling belowground biomass than those with few APA sites but only when exposed to exogenous auxin. As we observed different responses to exogenous auxin across the life cycle, we advocate for further studies of belowground traits and hormones at reproductive maturity. Studying phenotypic variation of genotypes across life stages and hormone environments will uncover additional shared patterns across traits, assisting efforts to potentially reach breeding targets and enhance our understanding of variation of genotypes in natural systems.

Low-concentration exogenous 3-indoleacetic acid improves fruit-setting rate of Marsdenia tenacissima by inhibiting the expression of embryo abortion-related genes.

Marsdenia tenacissima is a medicinal plant characterized by many flowers, few fruits, and a low fruit-setting rate. Exogenous auxins can improve the fruit-setting rate of plants; however, their impacts on M. tenacissima and regulatory mechanisms remain unclear. In this study, we conducted a field experiment to determine the fruit-setting rate, seed-setting rate, fruit size, and changes in transcriptional expression of related genes by spraying 10 and 50 mg·L-1 of 3-indoleacetic acid (IAA). The control plants were sprayed with distilled water. Our results indicated that the fruit-setting rate was 0.15 when treated with 10 mg·L-1 of IAA, which was 2.76-fold higher than that of the control. Compared with that of the control, the number of differentially expressed genes (DEGs) regulated by 10 mg·L-1 of IAA was 28.6-fold higher than that regulated by 50 mg·L-1 of IAA. These DEGs were closely related to hormone metabolism and fruit development. By transcriptome analysis, spraying 10 mg·L-1 of IAA increased the expressions of STP6, MYB17, and LAX3 and reduced those of CXE18, ILR1-like 3, and SAUR50; this possibly affected the ovule, embryo, and fruit development, thereby elevating the fruit-setting rate of M. tenacissima. Our results indicated that low IAA concentration increased the fruit-setting rate of M. tenacissima, providing theoretical and practical support for promoting the seed yield of M. tenacissima.

Transient efflux inhibition improves plant regeneration by natural auxins.

Plant genome editing and propagation are important tools in crop breeding and production. Both rely heavily on the development of efficient in vitro plant regeneration systems. Two prominent regeneration systems that are widely employed in crop production are somatic embryogenesis (SE) and de novo shoot regeneration. In many of the protocols for SE or shoot regeneration, explants are treated with the synthetic auxin analog 2,4-dichlorophenoxyacetic acid (2,4-D), since natural auxins, such as indole-3-acetic acid (IAA) or 4-chloroindole-3-acetic acid (4-Cl-IAA), are less effective or even fail to induce regeneration. Based on previous reports that 2,4-D, compared to endogenous auxins, is not effectively exported from plant cells, we investigated whether efflux inhibition of endogenous auxins could convert these auxins into efficient inducers of SE in Arabidopsis immature zygotic embryos (IZEs). We show that natural auxins and synthetic analogs thereof become efficient inducers of SE when their efflux is transiently inhibited by co-application of the auxin transport inhibitor naphthylphthalamic acid (NPA). Moreover, IZEs of auxin efflux mutants pin2 or abcb1 abcb19 show enhanced SE efficiency when treated with IAA or efflux-inhibited IAA, confirming that auxin efflux reduces the efficiency of Arabidopsis SE. Importantly, in contrast to the 2,4-D system, where only 50-60% of the embryos converted to seedlings, all SEs induced by transport-inhibited natural auxins converted to seedlings. Efflux-inhibited IAA, like 2,4-D, also efficiently induced SE from carrot suspension cells, whereas IAA alone could not, and efflux-inhibited 4-Cl-IAA significantly improved de novo shoot regeneration in Brassica napus. Our data provides new insights into the action of 2,4-D as an efficient inducer of plant regeneration but also shows that replacing this synthetic auxin for efflux-inhibited natural auxin significantly improves different types of plant regeneration, leading to a more synchronized and homogenous development of the regenerated plants.

In situ seasonal patterns of root auxin concentrations and meristem length in an arctic sedge.

Seasonal dynamics of root growth play an important role in large-scale ecosystem processes; they are largely governed by growth regulatory compounds and influenced by environmental conditions. Yet, our knowledge about physiological drivers of root growth is mostly limited to laboratory-based studies on model plant species. We sampled root tips of Eriophorum vaginatum and analyzed their auxin concentrations and meristem lengths biweekly over a growing season in situ in a subarctic peatland, both in surface soil and at the permafrost thawfront. Auxin concentrations were almost five times higher in surface than in thawfront soils and increased over the season, especially at the thawfront. Surprisingly, meristem length showed an opposite pattern and was almost double in thawfront compared with surface soils. Meristem length increased from peak to late season in the surface soils but decreased at the thawfront. Our study of in situ seasonal dynamics in root physiological parameters illustrates the potential for physiological methods to be applied in ecological studies and emphasizes the importance of in situ measurements. The strong effect of root location and the unexpected opposite patterns of meristem length and auxin concentrations likely show that auxin actively governs root growth to ensure a high potential for nutrient uptake at the thawfront.

Cell-layer specific roles for gibberellins in nodulation and root development.

Gibberellins (GA) have a profound influence on the formation of lateral root organs. However, the precise role this hormone plays in the cell-specific events during lateral root formation, rhizobial infection and nodule organogenesis, including interactions with auxin and cytokinin (CK), is not clear. We performed epidermal- and endodermal-specific complementation of the severely GA-deficient na pea (Pisum sativum) mutant with Agrobacterium rhizogenes. Gibberellin mutants were used to examine the spatial expression pattern of CK (TCSn)- and auxin (DR5)-responsive promoters and hormone levels. We found that GA produced in the endodermis promote lateral root and nodule organogenesis and can induce a mobile signal(s) that suppresses rhizobial infection. By contrast, epidermal-derived GA suppress infection but have little influence on root or nodule development. GA suppress the CK-responsive TCSn promoter in the cortex and are required for normal auxin activation during nodule primordia formation. Our findings indicate that GA regulate the checkpoints between infection thread (IT) penetration of the cortex and invasion of nodule primordial cells and promote the subsequent progression of nodule development. It appears that GA limit the progression and branching of IT in the cortex by restricting CK response and activate auxin response to promote nodule primordia development.

Protocol to synthesize the auxin analog 5-Ph-IAA for conditional protein depletion in C. elegans using the AID2 system.

The auxin-inducible degron (AID) system is a broadly used tool for spatiotemporal and reversible control of protein depletion in multiple experimental model systems. AID2 technology relies on a synthetic ligand, 5-phenyl-indole-3-acetic acid (5-Ph-IAA), for improved specificity and efficiency of protein degradation. Here, we provide a protocol for cost-effective 5-Ph-IAA synthesis utilizing the Suzuki coupling of 5-chloroindole and phenylboronic acid. We describe steps for evaluating the quality of lab-synthesized 5-Ph-IAA using a C. elegans AID2 tester strain.

Cytokinin and indole-3-acetic acid crosstalk is indispensable for silicon mediated chromium stress tolerance in roots of wheat seedlings.

The rising heavy metal contamination of soils imposes toxic impacts on plants as well as other life forms. One such highly toxic and carcinogenic heavy metal is hexavalent chromium [Cr(VI)] that has been reported to prominently retard the plant growth. The present study investigated the potential of silicon (Si, 10 µM) to alleviate the toxicity of Cr(VI) (25 µM) on roots of wheat (Triticum aestivum L.) seedlings. Application of Si to Cr(VI)-stressed wheat seedlings improved their overall growth parameters. This study also reveals the involvement of two phytohormones, namely auxin and cytokinin and their crosstalk in Si-mediated mitigation of the toxic impacts of Cr(VI) in wheat seedlings. The application of cytokinin alone to wheat seedlings under Cr(VI) stress reduced the intensity of toxic effects of Cr(VI). In combination with Si, cytokinin application to Cr(VI)-stressed wheat seedlings significantly minimized the decrease induced by Cr(VI) in different parameters such as root-shoot length (10.8% and 13%, respectively), root-shoot fresh mass (11.3% and 10.1%, respectively), and total chlorophyll and carotenoids content (13.4% and 6.8%, respectively) with respect to the control. This treatment also maintained the regulation of proline metabolism (proline content, and P5CS and PDH activities), ascorbate-glutathione (AsA-GSH) cycle and nutrient homeostasis. The protective effect of Si and cytokinin against Cr(VI) stress was minimized upon supplementation of an inhibitor of polar auxin transport- 2,3,5-triiodobenzoic acid (TIBA) which suggested a potential involvement of auxin in Si and cytokinin-mediated mitigation of Cr(VI) toxicity. The exogenous addition of a natural auxin - indole-3-acetic acid (IAA) confirmed auxin is an active member of a signaling cascade along with cytokinin that aids in Si-mediated Cr(VI) toxicity alleviation as IAA application reversed the negative impacts of TIBA on wheat roots treated with Cr(VI), cytokinin and Si. The results of this research are also confirmed by the gene expression analysis conducted for nutrient transporters (Lsi1, CCaMK, MHX, SULT1 and ZIP1) and enzymes involved in the AsA-GSH cycle (APX, GR, DHAR and MDHAR). The overall results of this research indicate towards possible induction of a crosstalk between cytokinin and IAA upon Si supplementation which in turn stimulates physiological, biochemical and molecular changes to exhibit protective effects against Cr(VI) stress. Further, the information obtained suggests probable employment of Si, cytokinin and IAA alone or combined in agriculture to maintain plant productivity under Cr(VI) stress and data regarding expression of key genes can be used to develop new crop varieties with enhanced resistance against Cr(VI) stress together with its reduced load in seedlings.

3,4-Dichlorophenylacetic acid acts as an auxin analog and induces beneficial effects in various crops.

Auxins and their analogs are widely used to promote root growth, flower and fruit development, and yield in crops. The action characteristics and application scope of various auxins are different. To overcome the limitations of existing auxins, expand the scope of applications, and reduce side effects, it is necessary to screen new auxin analogs. Here, we identified 3,4-dichlorophenylacetic acid (Dcaa) as having auxin-like activity and acting through the auxin signaling pathway in plants. At the physiological level, Dcaa promotes the elongation of oat coleoptile segments, the generation of adventitious roots, and the growth of crop roots. At the molecular level, Dcaa induces the expression of auxin-responsive genes and acts through auxin receptors. Molecular docking results showed that Dcaa can bind to auxin receptors, among which TIR1 has the highest binding activity. Application of Dcaa at the root tip of the DR5:GUS auxin-responsive reporter induces GUS expression in the root hair zone, which requires the PIN2 auxin efflux carrier. Dcaa also inhibits the endocytosis of PIN proteins like other auxins. These results provide a basis for the application of Dcaa in agricultural practices.

HiHo-AID2: boosting homozygous knock-in efficiency enables robust generation of human auxin-inducible degron cells.

Recent developments in auxin-inducible degron (AID) technology have increased its popularity for chemogenetic control of proteolysis. However, generation of human AID cell lines is challenging, especially in human embryonic stem cells (hESCs). Here, we develop HiHo-AID2, a streamlined procedure for rapid, one-step generation of human cancer and hESC lines with high homozygous degron-tagging efficiency based on an optimized AID2 system and homology-directed repair enhancers. We demonstrate its application for rapid and inducible functional inactivation of twelve endogenous target proteins in five cell lines, including targets with diverse expression levels and functions in hESCs and cells differentiated from hESCs.

The peptide GOLVEN10 alters root development and noduletaxis in Medicago truncatula.

The conservation of GOLVEN (GLV)/ROOT MERISTEM GROWTH FACTOR (RGF) peptide encoding genes across plant genomes capable of forming roots or root-like structures underscores their potential significance in the terrestrial adaptation of plants. This study investigates the function and role of GOLVEN peptide-coding genes in Medicago truncatula. Five out of fifteen GLV/RGF genes were notably upregulated during nodule organogenesis and were differentially responsive to nitrogen deficiency and auxin treatment. Specifically, the expression of MtGLV9 and MtGLV10 at nodule initiation sites was contingent upon the NODULE INCEPTION transcription factor. Overexpression of these five nodule-induced GLV genes in hairy roots of M. truncatula and application of their synthetic peptide analogues led to a decrease in nodule count by 25-50%. Uniquely, the GOLVEN10 peptide altered the positioning of the first formed lateral root and nodule on the primary root axis, an observation we term 'noduletaxis'; this decreased the length of the lateral organ formation zone on roots. Histological section of roots treated with synthetic GOLVEN10 peptide revealed an increased cell number within the root cortical cell layers without a corresponding increase in cell length, leading to an elongation of the root likely introducing a spatiotemporal delay in organ formation. At the transcription level, the GOLVEN10 peptide suppressed expression of microtubule-related genes and exerted its effects by changing expression of a large subset of Auxin responsive genes. These findings advance our understanding of the molecular mechanisms by which GOLVEN peptides modulate root morphology, nodule ontogeny, and interactions with key transcriptional pathways.

A Comprehensive Analysis of Auxin Response Factor Gene Family in Melastoma dodecandrum Genome.

Auxin Response Factors (ARFs) mediate auxin signaling and govern diverse biological processes. However, a comprehensive analysis of the ARF gene family and identification of their key regulatory functions have not been conducted in Melastoma dodecandrum, leading to a weak understanding of further use and development for this functional shrub. In this study, we successfully identified a total of 27 members of the ARF gene family in M. dodecandrum and classified them into Class I-III. Class II-III showed more significant gene duplication than Class I, especially for MedARF16s. According to the prediction of cis-regulatory elements, the AP2/ERF, BHLH, and bZIP transcription factor families may serve as regulatory factors controlling the transcriptional pre-initiation expression of MedARF. Analysis of miRNA editing sites reveals that miR160 may play a regulatory role in the post-transcriptional expression of MeARF. Expression profiles revealed that more than half of the MedARFs exhibited high expression levels in the stem compared to other organs. While there are some specific genes expressed only in flowers, it is noteworthy that MedARF16s, MedARF7A, and MedARF9B, which are highly expressed in stems, also demonstrate high expressions in other organs of M. dodecandrum. Further hormone treatment experiments revealed that these MedARFs were sensitive to auxin changes, with MedARF6C and MedARF7A showing significant and rapid changes in expression upon increasing exogenous auxin. In brief, our findings suggest a crucial role in regulating plant growth and development in M. dodecandrum by responding to changes in auxin. These results can provide a theoretical basis for future molecular breeding in Myrtaceae.

Study on Design, Synthesis and Herbicidal Activity of Novel 6-Indazolyl-2-picolinic Acids.

Thirty-eight new 4-amino-3,5-dicholo-6-(1H-indazolyl)-2-picolinic acids and 4-amino-3,5-dicholo-6-(2H-indazolyl)-2-picolinic acids were designed by scaffold hopping and synthesized to discover potential herbicidal molecules. All the new compounds were tested to determine their inhibitory activities against Arabidopsis thaliana and the root growth of five weeds. In general, the synthesized compounds exhibited excellent inhibition properties and showed good inhibitory effects on weed root growth. In particular, compound 5a showed significantly greater root inhibitory activity than picloram in Brassica napus and Abutilon theophrasti Medicus at the concentration of 10 µM. The majority of compounds exhibited a 100% post-emergence herbicidal effect at 250 g/ha against Amaranthus retroflexus and Chenopodium album. We also found that 6-indazolyl-2-picolinic acids could induce the up-regulation of auxin genes ACS7 and NCED3, while auxin influx, efflux and auxin response factor were down-regulated, indicating that 6-indazolyl-2-picolinic acids promoted ethylene release and ABA production to cause plant death in a short period, which is different in mode from other picolinic acids.