Auxin Biosynthesis Research Articles

Emerging Arabidopsis roots exhibit hypersensitive gravitropism associated with distinctive auxin synthesis and polar transport within the elongation zone

Gravitropism is crucial for plants to secure light, water, and minerals essential for developing seedlings. Despite its importance, the gravitropism of young roots remains largely unexplored. Herein, we reported that the emerging Arabidopsis roots exhibit hypersensitive gravitropism compared to mature roots, growing relatively slowly but bending exceptionally rapidly. This rapid gravibending is characterized by substantial growth inhibition and a distinctive auxin accumulation on the lower side of the elongation zone. Intriguingly, surgical experiments suggest that these auxins predominantly originate from the elongation zone rather than from the shoot or root cap. However, their asymmetrical distribution is heavily modulated by the root cap. Confocal analysis of GFP-tagged TAA1 further confirms that gravitational stimulus induces active auxin biosynthesis in the elongation zone of nascent roots but not in mature roots. Furthermore, mutations in the PIN proteins, especially PIN2, severely impair the rapid gravitropic responses in emerging roots. Interestingly, PIN2 in nascent roots is not confined to the epidermis and cortex but extends to the endodermis, contrasting with its distribution in mature roots. Gravitational stimulation leads to a marked asymmetrical distribution of PIN2 between the upper and lower sides of the roots, which is strongly inhibited by surgical removal of the root cap. These observations indicate that gravitational stimulation triggers active auxin synthesis and PIN protein-mediated lateral transport within the elongation zone of emerging roots, resulting in swift gravitropic responses. These results offer an intriguing enhancement and expansion to the mechanism of root gravitropism.

Integrated Metabolomic, Lipidomic and Proteomic Analysis Define the Metabolic Changes Occurring in Curled Areas in Leaves With Leaf Peach Curl Disease.

Peach Leaf Curl Disease, caused by Taphrina deformans, is characterized by reddish hypertrophic and hyperplasic leaf areas. To comprehend the biochemical imbalances caused by the fungus, dissected symptomatic (C) and asymptomatic areas (N) from leaves with increasing disease extension were analyzed by an integrated approach including metabolomics, lipidomics, proteomics, and complementary biochemical techniques. Drastic metabolic differences were identified in C areas with respect to either N areas or healthy leaves, including altered chloroplastic functioning and composition, which differs from the typical senescence process. In C areas, alteration in redox-homoeostasis proteins and in triacylglycerols content, peroxidation and double bond index were observed. Proteomic data revealed induction of host enzymes involved in auxin and jasmonate biosynthesis and an upregulation of phenylpropanoid and mevalonate pathways and downregulation of the plastidic methylerythritol phosphate route. Amino acid pools were affected, with upregulation of proteins involved in asparagine synthesis. Curled areas exhibited a metabolic shift towards functioning as a sink tissue importing sugars, probably from N areas, and producing energy through fermentation and respiration and reductive power via the pentose phosphate route. Identifying the metabolic disturbances leading to disease symptoms is a key step in designing strategies to prevent or delay the progression of the disease.

ASYMMETRIC LEAVES1 promotes leaf hyponasty in Arabidopsis by light-mediated auxin signaling.

In plants, balancing growth and environmental responses is crucial for maximizing fitness. Close proximity among plants and canopy shade, which negatively impacts reproduction, elicits morphological adjustments such as hypocotyl growth and leaf hyponasty, mainly through changes in light quality and auxin levels. However, how auxin, synthesized from a shaded leaf blade, distally induces elongation of hypocotyl and petiole cells remains to be elucidated. We demonstrated that ASYMMETRIC LEAVES1 (AS1) promotes leaf hyponasty through the regulation of auxin biosynthesis, polar auxin transport, and auxin signaling genes in Arabidopsis (Arabidopsis thaliana). AS1 overexpression leads to elongation of the abaxial petiole cells with auxin accumulation in the petiole, resulting in hyponastic growth, which is abolished by the application of an auxin transport inhibitor to the leaf blade. In addition, the as1 mutant exhibits reduced hypocotyl growth under shade conditions. We observed that AS1 protein accumulates in the nucleus in response to shade or far-red light. Chromatin immunoprecipitation analysis identified the association of AS1 with the promoters of YUCCA8 (YUC8) and INDOLE-3-ACETIC ACID INDUCIBLE 19 (IAA19). In addition, AS1 forms complexes with PHYTOCHROME INTERACTING FACTORs in the nucleus and synergistically induces YUC8 and IAA19 expression. Our findings suggest that AS1 plays a crucial role in facilitating phenotypic plasticity to the surroundings by connecting light and phytohormone action.

A coherent feed-forward loop in the Arabidopsis root stem cell organizer regulates auxin biosynthesis and columella stem cell maintenance.

Stem cells in plant meristems are kept undifferentiated by signals from surrounding cells and provide the basis for continuous organ formation. In the stem cell organizer of the Arabidopsis thaliana root, the quiescent centre (QC), the WOX5 transcription factor, functions as a central hub in regulating columella stem cell (CSC) homoeostasis. However, the processes mediating WOX5 function are only poorly understood. Here we identify the transcription factor HAN as a central mediator of WOX5-regulated stem cell maintenance. HAN is required for mitotic quiescence of QC and CSC maintenance and is sufficient to induce ectopic stem cells. WOX5 and HAN repress transcription of the differentiation factor gene CDF4 in a coherent feed-forward loop (cFFL), one output of which is the expression of the auxin biosynthesis gene TAA1 and maintenance of auxin response maxima in the organizer. These findings and mathematical modelling provide a mechanistic framework for WOX5 function in the root stem cell niche.

The AP2 transcription factor BARE RECEPTACLE regulates floral organogenesis via auxin pathways in woodland strawberry.

During flower development, different floral organs are formed to ensure fertilization and fruit set. Although the genetic networks underlying flower development are increasingly well understood, less is known about the mechanistic basis in different species. Here, we identified a mutant of woodland strawberry (Fragaria vesca), bare receptacle (bre), which produces flowers with greatly reduced carpels and other floral organs. Genetic analysis revealed that BRE encodes an APETALA2 (AP2) transcription factor. BRE was highly expressed in floral meristems and floral organ primordia. BRE could directly bind the GCC-box motif in the YUCCA (YUC) auxin biosynthesis genes FveYUC4 and FveYUC2 and promote their expression. The yuc4 mutant had fewer floral organs, and the bre yuc4 double mutant had similar numbers of petals and carpels to bre. Auxin homeostasis and distribution were severely disrupted in bre. Although auxin application or FveYUC4 overexpression did not rescue the bre phenotypes, bre was hypersensitive to treatment with the polar auxin transport inhibitor N-1-naphthylphthalamic acid (NPA). In addition, BRE was able to directly bind and regulate the expression of five other auxin pathway genes. Overall, these results demonstrate that BRE is required for floral organogenesis, particularly carpel initiation, and acts through the auxin pathway in strawberry.

Identification and analysis of imprinted genes in wild strawberry uncover a regulatory pathway in endosperm development.

Fertilization is a fundamental process that triggers seed and fruit development, but the molecular mechanisms underlying fertilization-induced seed development are poorly understood. Previous research has established AGamous-Like62 (AGL62) activation and auxin biosynthesis in the endosperm as key events following fertilization in Arabidopsis (Arabidopsis thaliana) and wild strawberry (Fragaria vesca). To test the hypothesis that epigenetic mechanisms are critical in mediating the effect of fertilization on the activation of AGL62 and auxin biosynthesis in the endosperm, we first identified and analyzed imprinted genes from the endosperm of wild strawberry. We isolated endosperm tissues from F1 seeds of two wild strawberry Fragaria vesca subspecies, generated endosperm-enriched transcriptomes, and identified candidate Maternally-Expressed and Paternally-Expressed Genes (MEGs and PEGs). Through bioinformatic analyses, we identified four imprinted genes that may be involved in regulating the expression of FveAGL62 and auxin biosynthesis genes. We conducted functional analysis of a maternally expressed gene FveMYB98 through CRISPR-knockout and overexpression in transgenic strawberry as well as analysis in heterologous systems. FveMYB98 directly repressed FveAGL62 at stage 3 endosperm, which likely serves to limit auxin synthesis and endosperm proliferation. These results provide an inroad into the regulation of early stage seed development by imprinted genes in strawberry, suggest potential function of imprinted genes in parental conflict, and identify FveMYB98 as a regulator of a key transition point in endosperm development.

Genome-wide gene network uncover temporal and spatial changes of genes in auxin homeostasis during fruit development in strawberry (F. × ananassa)

BackgroundThe plant hormone auxin plays a crucial role in regulating important functions in strawberry fruit development. Although a few studies have described the complex auxin biosynthetic and signaling pathway in wild diploid strawberry (Fragaria vesca), the molecular mechanisms underlying auxin biosynthesis and crosstalk in octoploid strawberry fruit development are not fully characterized. To address this knowledge gap, comprehensive transcriptomic analyses were conducted at different stages of fruit development and compared between the achene and receptacle to identify developmentally regulated auxin biosynthetic genes and transcription factors during the fruit ripening process. Similar to wild diploid strawberry, octoploid strawberry accumulates high levels of auxin in achene compared to receptacle.ResultsGenes involved in auxin biosynthesis and conjugation, such as Tryptophan Aminotransferase of Arabidopsis (TAAs), YUCCA (YUCs), and Gretchen Hagen 3 (GH3s), were found to be primarily expressed in the achene, with low expression in the receptacle. Interestingly, several genes involved in auxin transport and signaling like Pin-Formed (PINs), Auxin/Indole-3-Acetic Acid Proteins (Aux/IAAs), Transport Inhibitor Response 1 / Auxin-Signaling F-Box (TIR/AFBs) and Auxin Response Factor (ARFs) were more abundantly expressed in the receptacle. Moreover, by examining DEGs and their transcriptional profiles across all six developmental stages, we identified key auxin-related genes co-clustered with transcription factors from the NAM-ATAF1,2-CUC2/ WRKYGQK motif (NAC/WYKY), Heat Shock Transcription Factor and Heat Shock Proteins (HSF/HSP), APETALA2/Ethylene Responsive Factor (AP2/ERF) and MYB transcription factor groups.ConclusionsThese results elucidate the complex regulatory network of auxin biosynthesis and its intricate crosstalk within the achene and receptacle, enriching our understanding of fruit development in octoploid strawberries.

The bifunctional transcription factor NAC32 modulates nickel toxicity responses through repression of root-nickel compartmentalization and activation of auxin biosynthesis

Nickel (Ni) is an important micronutrient, but excess Ni is toxic to many plant species. Currently, relatively little is known about the genetic basis of the plant responses to Ni toxicity. Here, we demonstrate that NAC32 transcription factor functions as a core genetic hub to regulate the Ni toxicity responses in Arabidopsis. NAC32 negatively regulates root-Ni concentration through the IREG2 (IRON REGULATED2) encoding a transporter. NAC32 also induces local auxin biosynthesis in the root-apex transition zone by upregulating YUCCA 7 (YUC7)/8/9 expression, which results in a local enhancement of auxin signaling in root tips, especially under Ni toxicity, thereby impaired primary root growth. By analyses of various combinations of nac32 and ireg2 mutants, as well as nac32 and yuc7/8/9 triple mutants, including high-order quadruple mutant, we demonstrated that NAC32 negatively regulates Ni stress tolerance by acting upstream of IREG2 and YUC7/8/9 to modulate their function in Ni toxicity responses. ChIPqPCR, EMSA (electrophoretic mobility shift assay) and transient dual-LUC reporter assays showed that NAC32 transcriptionally represses IREG2 expression but activates YUC7/8/9 expression by directly binding to their promoters. Our work demonstrates that NAC32 coordinates Ni compartmentation and developmental plasticity in roots, providing a conceptual framework for understanding Ni toxicity responses in plants.

Molecular and cytogenetic characterization of Osteospermum fruticosum lines harboring wild type pRi rol genes.

Transgenic lines engineered through wild type Rhizobium rhizogenes display an altered phenotype known as the Ri phenotype. This phenotype includes a more compact plant habit, which has proved useful to obtain more compact varieties that require less chemical growth regulation. Here, we develop a method for the molecular and cytogenetic characterization of Cape daisy (Osteospermum fruticosum Norl.) Ri lines in order to predict segregation of pRi T-DNA genes. Analysis of copy number variation (CNV) by means of digital PCR indicated large variation in the copy number of the inserted root oncogenic loci (rol) genes, ranging from 1 to more than 15 copies. In addition, up to 9 copies of the auxin biosynthesis genes (aux) were present in a single Ri line. Visualization of pRiA4 and pRi1724 rol and aux insertion in 4 Ri lines was performed through Fluorescence In Situ Hybridization. The number of rol integrated loci varied from 1 to 3 loci. In contrast, the different TR-gene copies were confined to a single locus which consistently co-localized with a TL locus, this was demonstrated for the first time. Based on CNV and FISH a single Ri line, harboring 7 pRi1724 rol gene copies dispersed over 3 integration loci, was selected for breeding. Copy number segregation in R1 progeny of 2, 3, 4 and 5 pRi1724 copies was confirmed, indicating that the evaluation of the breeding value of first generation Ri lines is possible through CNV and FISH.

Advances in Plant Auxin Biology: Synthesis, Metabolism, Signaling, Interaction with Other Hormones, and Roles under Abiotic Stress.

Auxin is a key hormone that regulates plant growth and development, including plant shape and sensitivity to environmental changes. Auxin is biosynthesized and metabolized via many parallel pathways, and it is sensed and transduced by both normal and atypical pathways. The production, catabolism, and signal transduction pathways of auxin primarily govern its role in plant growth and development, and in the response to stress. Recent research has discovered that auxin not only responds to intrinsic developmental signals, but also mediates various environmental signals (e.g., drought, heavy metals, and temperature stresses) and interacts with hormones such as cytokinin, abscisic acid, gibberellin, and ethylene, all of which are involved in the regulation of plant growth and development, as well as the maintenance of homeostatic equilibrium in plant cells. In this review, we discuss the latest research on auxin types, biosynthesis and metabolism, polar transport, signaling pathways, and interactions with other hormones. We also summarize the important role of auxin in plants under abiotic stresses. These discussions provide new perspectives to understand the molecular mechanisms of auxin's functions in plant development.

The knockout of SlMTC impacts tomato seed size and reduces resistance to salt stress in tomato

Members of the MT-A70 family are key catalytic proteins involved in m6A methylation modifications in plants. They play diverse roles at the posttranscriptional level by regulating RNA secondary structure, selective splicing, stability, and translational efficiency, which collectively affect plant growth, development, and stress responses. In this study, we explored the function of the gene SlMTC, a Class C member of the MT-A70 family, in tomatoes by using CRISPR/Cas9 technology. Compared with the wild-type (WT), the CR-slmtc mutants exhibited decreased seed size and slower growth rates during the seedling stage, along with weaker salt tolerance and significant downregulation of stress-related genes, such as PR1, PR5, and P5CS. The qRT-PCR results revealed that the expression levels of genes involved in auxin biosynthesis (FZY1, FZY3, and FZY4) and polar transport (PIN1, PIN4, and PIN8) were lower in CR-slmtc plants than in the WT plants. In addition, yeast two-hybrid assays showed that SlMTC could interact with SlMTA, a Class A member of the MT-A70 family, providing insights into the potential mode of action of SlMTC in tomatoes. Overall, our findings indicate the critical role of SlMTC in plant growth and development as well as in response to salt stress.

Genetically Encoded, Noise-Tolerant, Auxin Biosensors in Yeast.

Auxins are crucial signaling molecules that regulate the growth, metabolism, and behavior of various organisms, most notably plants but also bacteria, fungi, and animals. Many microbes synthesize and perceive auxins, primarily indole-3-acetic acid (IAA, referred to as auxin herein), the most prevalent natural auxin, which influences their ability to colonize plants and animals. Understanding auxin biosynthesis and signaling in fungi may allow us to better control interkingdom relationships and microbiomes from agricultural soils to the human gut. Despite this importance, a biological tool for measuring auxin with high spatial and temporal resolution has not been engineered in fungi. In this study, we present a suite of genetically encoded, ratiometric, protein-based auxin biosensors designed for the model yeast Saccharomyces cerevisiae. Inspired by auxin signaling in plants, the ratiometric nature of these biosensors enhances the precision of auxin concentration measurements by minimizing clonal and growth phase variation. We used these biosensors to measure auxin production across diverse growth conditions and phases in yeast cultures and calibrated their responses to physiologically relevant levels of auxin. Future work will aim to improve the fold change and reversibility of these biosensors. These genetically encoded auxin biosensors are valuable tools for investigating auxin biosynthesis and signaling in S. cerevisiae and potentially other yeast and fungi and will also advance quantitative functional studies of the plant auxin perception machinery, from which they are built.

Enhancing saffron (Crocus sativus L.) growth in the Kashmir valley with resilient and widely effective Plant Growth-Promoting Rhizobacteria (PGPR) under field conditions

This study provides a thorough examination of stress-tolerant plant growth-promoting rhizobacteria (PGPR) and their significance in enhancing plant growth and biocontrol activities, and influence on saffron cultivation in the Kashmir Valley. Quantitative analysis of 35 efficient PGPR revealed significant variability in plant growth promotion (PGP) attributes ranging from 60 to 653 µg/ml tri-calcium phosphate (TCP) solubilization, 1548–4311 nM α-ketobutyrate h/mg/protein ACC-deaminase activity, 1.4–74.8 µg/ml IAA-like auxins production, and 94–214 % siderophore production. Molecular fingerprinting disclosed 52 ERIC types that belonged to 25 genera, mainly Bacillus. Bacillus species including B. aryabhattai, B. halotolerans, B. methylotrophicus, B. safensis, B. siamensis and B. simplex dominated the PGPR population, along with Pseudomonas spp., such as P. azotoformans and P. chlororaphis, indicating a selective buildup of PGPR in the saffron rhizosphere. In-vivo and In-vitro dual inoculation test of these widespread PGPR and stress-tolerant also inhibited the mycelial growth of Fusarium species including F. oxysporum, F. oxysporum f. sp. ciceris, and F. proliferatum. The field application of seven selected PGPR strains resulted in significant improvements in saffron productivity, including increased sprouted corms, plant height, stigma length, and stigma fresh and dry weight, which ranged from 0.6-1.8 %, 0.4–0.7 %, 0.3–0.5 %, and 6–19 %, respectively. These strains have the potential to stimulate cormlet growth and ultimately increase saffron production. Therefore, the PGP traits of these stress-tolerant rhizobacteria contributing to nutrients solubilization, auxin biosynthesis, and fungicidal attributes can ameliorate the saffron agricultural practices.

Anchorene, a carotenoid-derived growth regulator, modulates auxin homeostasis by suppressing GH3-mediated auxin conjugation.

Anchorene, identified as an endogenous bioactive carotenoid-derived dialdehyde and diapocarotenoid, affects root development by modulating auxin homeostasis. However, the precise interaction between anchorene and auxin, as well as the mechanisms by which anchorene modulates auxin levels, remain largely elusive. In this study, we conducted a comparative analysis of anchorene's bioactivities alongside auxin and observed that anchorene induces multifaceted auxin-like effects. Through genetic and pharmacological examinations, we revealed that anchorene's auxin-like activities depend on the indole-3-pyruvate-dependent auxin biosynthesis pathway, as well as the auxin inactivation pathway mediated by Group II Gretchen Hagen 3 (GH3) proteins that mainly facilitate the conjugation of indole-3-acetic acid (IAA) to amino acids, leading to the formation of inactivated storage forms. Our measurements indicated that anchorene treatment elevates IAA levels while reducing the quantities of inactivated IAA-amino acid conjugates and oxIAA. RNA sequencing further revealed that anchorene triggers the expression of numerous auxin-responsive genes in a manner reliant on Group II GH3s. Additionally, our in vitro enzymatic assays and biolayer interferometry (BLI) assay demonstrated anchorene's robust suppression of GH3.17-mediated IAA conjugation with glutamate. Collectively, our findings highlight the significant role of carotenoid-derived metabolite anchorene in modulating auxin homeostasis, primarily through the repression of GH3-mediated IAA conjugation and inactivation pathways, offering novel insights into the regulatory mechanisms of plant bioactive apocarotenoids.

Transcriptomic profiling reveals histone acetylation-regulated genes involved in somatic embryogenesis in Arabidopsis thaliana

BackgroundSomatic embryogenesis (SE) exemplifies the unique developmental plasticity of plant cells. The regulatory processes, including epigenetic modifications controlling embryogenic reprogramming of cell transcriptome, have just started to be revealed.ResultsTo identify the genes of histone acetylation-regulated expression in SE, we analyzed global transcriptomes of Arabidopsis explants undergoing embryogenic induction in response to treatment with histone deacetylase inhibitor, trichostatin A (TSA). The TSA-induced and auxin (2,4-dichlorophenoxyacetic acid; 2,4-D)-induced transcriptomes were compared. RNA-seq results revealed the similarities of the TSA- and auxin-induced transcriptomic responses that involve extensive deregulation, mostly repression, of the majority of genes. Within the differentially expressed genes (DEGs), we identified the master regulators (transcription factors - TFs) of SE, genes involved in biosynthesis, signaling, and polar transport of auxin and NITRILASE-encoding genes of the function in indole-3-acetic acid (IAA) biosynthesis. TSA-upregulated TF genes of essential functions in auxin-induced SE, included LEC1/LEC2, FUS3, AGL15, MYB118, PHB, PHV, PLTs, and WUS/WOXs. The TSA-induced transcriptome revealed also extensive upregulation of stress-related genes, including those related to stress hormone biosynthesis. In line with transcriptomic data, TSA-induced explants accumulated salicylic acid (SA) and abscisic acid (ABA), suggesting the role of histone acetylation (Hac) in regulating stress hormone-related responses during SE induction. Since mostly the adaxial side of cotyledon explant contributes to SE induction, we also identified organ polarity-related genes responding to TSA treatment, including AIL7/PLT7, RGE1, LBD18, 40, HB32, CBF1, and ULT2. Analysis of the relevant mutants supported the role of polarity-related genes in SE induction.ConclusionThe study results provide a step forward in deciphering the epigenetic network controlling embryogenic transition in somatic cells of plants.

Genome-wide analysis of Citrus medica ABC transporters reveals the regulation of fruit development by CmABCB19 and CmABCC10

ATP-binding cassette (ABC) transporters are vital for plant growth and development as they facilitate the transport of essential molecules. Despite the family's significance, limited information exists about its functional distinctions in Citrus medica. Our study identified 119 genes encoding ABC transporter proteins in the C. medica genome. Through an evolutionary tree and qPCR analysis, two ABC genes, CmABCB19 and CmABCC10, were implicated in C. medica fruit development, showing upregulation in normal fruits compared to malformed fruits. CmABCB19 was found to localize to the plasma membrane of Nicotiana tabacum, exhibiting indole-3-acetic acid (IAA) efflux activity in the yeast mutant strain yap1. CmABCC10, a tonoplast-localized transporter, exhibited efflux of diosmin, nobiletin, and naringin, with rutin influx in strain ycf1. Transgenic expression of CmABCB19 and CmABCC10 in Arabidopsis thaliana induced alterations in auxin and flavonoid content, impacting silique and seed size. This effect was attributed to the modulation of structural genes in the auxin biosynthesis (YUC5/9, CYP79B2, CYP83B1, SUR1) and flavonoid biosynthesis (4CL2/3, CHS, CHI, FLS1/3) pathways. In summary, the functional characterization of CmABCB19 and CmABCC10 illuminates auxin and flavonoid transport, offering insights into their interplay with biosynthetic pathways and providing a foundation for understanding the transporter's role in fruit development.

Coordination of miR319-TaPCF8 with TaSPL14 orchestrates auxin signaling and biosynthesis to regulate plant height in common wheat.

Wheat culms, comprising four to six internodes, are critically involved in determining plant height and lodging resistance, essential factors for field performance and regional adaptability. This study revealed the regulatory function of miR319 in common wheat plant height. Repression of tae-miR319 through short tandem target mimics (STTM) caused an increased plant height, while overexpression (OE) of tae-miR319 had the opposite effect. Overexpressing a miR319-resistant target gene TaPCF8 (rTaPCF8), increased plant height. TaPCF8 acted as a transcription repressor of downstream genes TaIAAs, which interact physically with TaSPL14. The significant differences of indole-3-acetic acid (IAA) contents indicate the involvement of auxin pathway in miR319-mediated plant height regulation. Finally, we identified two TaPCF8 haplotypes in global wheat collections. TaPCF8-5A-Hap2, as per association and evolution examinations, was subjected to strong substantial selection throughout wheat breeding. This haplotype, associated with shorter plant height, aligns with global breeding requirements. Consequently, in high-yield wheat breeding, we proposed a potential molecular marker for marker-assisted selection (MAS). Our findings offer fresh perspectives into the molecular mechanisms that underlie the miR319-TaPCF8 module's regulation of plant height by orchestrating auxin signaling and biosynthesis in wheat.

The ectomycorrhizal fungus Scleroderma bovista improves growth of hazelnut seedlings and plays a role in auxin signaling and transport.

Scleroderma bovista can form symbiotic ectomycorrhizal fungi with hazel roots. The mechanism through which S. bovista promotes hazelnut growth remains unclear. This study aimed to evaluate the effect of ectomycorrhizal fungus S. bovista on the growth and development of hazel roots and gene expression changes through comparative transcriptome analysis. After inoculation with S. bovista, the fungus symbiotically formed ectomycorrhiza with hazel roots. The fresh weights of the aboveground and underground parts of My treatment (inoculated with S. bovista and formed mycorrhiza) were much higher than those of the control, respectively. The length, project area, surface area, volume, forks, and diameter of the inoculated seedlings root were 1.13 to 2.48 times higher than those of the control. In the paired comparison, 3,265 upregulated and 1,916 downregulated genes were identified. The most significantly enriched Gene Ontology term for the upregulated Differentially Expressed Genes was GO:0005215 (transporter activity). Immunohistochemical analysis suggested that the expression levels of auxin and Auxin Response Factor9 were significantly increased by S. bovista after the formation of mycorrhizal fungi in hazelnut root tips. These results indicate that genes related to auxin biosynthesis, transport and signaling, and transport of nutrients may contribute to root development regulation in hazel ectomycorrhiza.

The monokaryotic filamentous fungus Ustilago sp. HFJ311 promotes plant growth and reduces Cd accumulation by enhancing Fe transportation and auxin biosynthesis

Infection with smut fungus like Ustilago maydis decreases crop yield via inducing gall formation. However, the in vitro impact of Ustilago spp. on plant growth and stress tolerance remains elusive. This study investigated the plant growth promotion and cadmium stress mitigation mechanisms of a filamentous fungus discovered on a cultural medium containing 25 μM CdCl2. ITS sequence alignment revealed 98.7 % similarity with Ustilago bromivora, naming the strain Ustilago sp. HFJ311 (HFJ311). Co-cultivation with HFJ311 significantly enhanced the growth of various plants, including Arabidopsis, tobacco, cabbage, carrot, rice, and maize, and improved Arabidopsis tolerance to abiotic stresses like salt and metal ions. HFJ311 increased chlorophyll and Fe contents in Arabidopsis shoots and enhanced root-to-shoot Fe translocation while decreasing root Fe concentration by approximately 70 %. Concurrently, HFJ311 reduced Cd accumulation in Arabidopsis by about 60 %, indicating its potential for bioremediation in Cd-contaminated soils. Additionally, HFJ311 stimulated IAA concentration by upregulating auxin biosynthesis genes. Overexpression of the Fe transporter IRT1 negated HFJ311's growth-promotion effects under Cd stress. These results suggest that HFJ311 stimulates plant growth and inhibits Cd uptake by enhancing Fe translocation and auxin biosynthesis while disrupting Fe absorption. Our findings offer a promising bioremediation strategy for sustainable agriculture and food security.

TMK4-mediated FIP37 phosphorylation regulates auxin-triggered N6-methyladenosine modification of auxin biosynthetic genes in Arabidopsis

The dynamics of N6-methyladenosine (m6A) mRNA modification are tightly controlled by the m6A methyltransferase complex and demethylases. Here, we find that auxin treatment alters m6A modification on auxin-responsive genes. Mechanically, TRANSMEMBRANE KINASE 4 (TMK4), a component of the auxin signaling pathway, interacts with and phosphorylates FKBP12-INTERACTING PROTEIN 37 (FIP37), a core component of the m6A methyltransferase complex, in an auxin-dependent manner. Phosphorylation of FIP37 enhances its interaction with RNA, thereby increasing m6A modification on its target genes, such as NITRILASE 1 (NIT1), a gene involved in indole-3-acetic acid (IAA) biosynthesis. 1-Naphthalacetic acid (NAA) treatment accelerates the mRNA decay of NIT1, in a TMK4- and FIP37-dependent manner, which leads to inhibition of auxin biosynthesis. Our findings identify a regulatory mechanism by which auxin modulates m6A modification through the phosphorylation of FIP37, ultimately affecting mRNA stability and auxin biosynthesis in plants.