Rapid Auxin-Mediated Cell Expansion

DUO1 Activated Zinc Finger (AtDAZ) protein role in the generative cell body morphogenesis

Arabidopsis MYB transcription factor, AtDUO1 regulates generative cell body (GC) morphogenesis from round to semi and fully elongated forms before pollen mitosis-II (PM II). It was hypothesised that DUO1 might regulate morphogenesis through any of its direct target genes or components of the DUO1-DAZ1 network. The developmental analysis of plants harbouring T-DNA insertions in some DUO1 target genes using light and fluorescence microscopy revealed abnormal GC morphogenesis only in daz1 and daz2, but gcs1, trm16, mapkkk10, mapkkk20, tet11, and tip1 all undergo normal elongation indicating that these target genes have no important roles in morphogenesis or may be redundant. The important regulatory role of DUO1 was confirmed through the observed incomplete rescue of morphogenesis of mutant duo1-1 GCs by DAZ1 and independently by a C-terminally deleted version of DUO1 (DUO1∆C3) lacking activation sequences. The evidence supports the important role of DAZ1 in GC shape partial morphogenesis. The C-terminus of DUO1 may regulate some target genes that affect GC body elongation. Furthermore, an intact DUO1 is shown to be indispensable for GC shape and nucleus elongation and subsequently for timely division and sperm cell morphogenesis. The development of the GC cytoplasmic projection is regulated independently of DUO1, and all its target genes were able to form it.

Transcriptional Analysis of Tissues in Tartary Buckwheat Seedlings Under IAA Stimulation

Background:Fagopyrum tataricum, commonly referred to as tartary buckwheat, is a cultivated medicinal and edible crop renowned for its economic and nutritional significance. Following the publication of the buckwheat genome, research on its functional genomics across various growth environments has gradually begun. Auxin plays a crucial role in many life processes. Analyzing the expression changes in tartary buckwheat after IAA treatment is of great significance for understanding its growth and environmental adaptability. Methods: This study investigated the changes in auxin response during the buckwheat seedling stage through high-throughput transcriptome sequencing and the identification and annotation of differentially expressed genes (DEGs) across three treatment stages. Results: After IAA treatment, there are 3355 DEGs in leaves and 3974 DEGs in roots identified. These DEGs are significantly enriched in plant hormone signaling, MAPK signaling pathways, phenylpropanoid biosynthesis, and flavonoid biosynthesis pathways. This result suggests a notable correlation between these tissues in buckwheat and their response to IAA, albeit with significant differences in response patterns. Additionally, the identification of tissue-specific expression genes in leaves and other tissues revealed distinct tissue variations. Conclusions: Following IAA treatment, an increase in tissue-specific expression genes observed, indicating that IAA significantly regulates the growth of buckwheat tissues. This study also validated certain genes, particularly those in plant hormone signaling pathways, providing a foundational dataset for the further analysis of buckwheat growth and tissue development and laying the groundwork for understanding buckwheat growth and development.

Superoxide anions induce tension wood formation by promoting cambium cell activity

Tension wood (TW), characterized by increased cambium cell proliferation and few vessels, is a classical model for the mechanical analysis of wood formation. In this study, we found higher superoxide anion (O2.-) levels in the cambium zone of poplar (Populus alba × P. glandulosa clone "84K") TW than in that of opposite wood during gravistimulation. Treatment with an O2.- activator (methyl viologen) resulted in tension-wood-like xylem tissue formation, and transgenic plants with reduced cambium O2.- levels presented an attenuated gravity response. Time-course detection of O2.- and indole-3-acetic acid (IAA) levels revealed that auxin responses were enhanced following increases in O2.- levels, suggesting that IAA mediates TW induction downstream of O2.-. Rapid division but advanced programmed cell death in cambium cells was detected in both gravistimulated and O2.- activator-treated plants. These findings suggest that high O2.- levels trigger downstream IAA signaling to promote cambium cell proliferation and induce TW formation.

Regulation of PILS genes by bZIP transcription factor TGA7 in tomato plant growth

Auxin plays a pivotal role in plant growth regulation. The PIN-FORMED (PIN) proteins facilitate long-distance polar auxin transport, whereas the recently identified PIN-LIKES (PILS) proteins regulate intracellular auxin homeostasis. However, the auxin transport mechanisms in horticultural crops remain largely unexplored. Here, we identified and characterized PILS genes in tomato (Solanum lycopersicum). Promoter analysis revealed enrichment in TGA[C/T]G motifs, suggesting transcriptional regulation by TGA factors in the bZIP family. Subcellular localization studies confirmed that all tomato PILS proteins localize in the endoplasmic reticulum. PILS2 exhibited the highest expression across examined tissues, and its close homologue PILS6 showed a similar but less pronounced expression pattern. Silencing PILS2 significantly inhibited shoot and root growth. Phylogenetic and expression analyses identified the homologs of Arabidopsis TGA1, TGA3, TGA4, and TGA7 in tomato genome, with tomato TGA7 showing higher expression in roots. Notably, silencing tomato TGA7, but not TGA1, TGA3, or TGA4, strongly impaired shoot and root growth. Molecular assays demonstrated that TGA7 directly binds to the PILS2 promoter to activate its transcription. These findings uncover a TGA7-PILS2 regulatory module that governs plant growth and offer new insights into the function and regulation of PILS genes in tomato.

Phytohormones involved in vascular cambium activity in woods: current progress and future challenges

Vascular cambium is the continuation of meristem activity at the top of plants, which promotes lateral growth of plants. The vascular cambium evolved as an adaptation for secondary growth, initially in early seed plants, and became more refined in the evolution of gymnosperms and angiosperms. In angiosperms, it is crucial for plant growth and wood formation. The vascular cambium is regulated by a complex interplay of phytohormones, which are chemical messengers that coordinate various aspects of plant growth and development. This paper synthesizes the current knowledge on the regulatory effects of primary plant hormones and peptide signals on the development of the cambium in forest trees, and it outlines the current research status and future directions in this field. Understanding these regulatory mechanisms holds significant potential for enhancing our ability to manage and cultivate forest tree species in changing environmental conditions.

ABI3 regulates ABI1 function to control cell length in primary root elongation zone

Post-embryonic primary root growth is effectively an interplay of several hormone signalling pathways. Here, we show that the ABA-responsive transcription factor ABI3 controls primary root growth through the regulation of JA signalling molecule JAZ1 along with ABA-responsive factor ABI1. In the absence of ABI3, the primary root elongation zone is shortened with significantly reduced cell length. Expression analyses and ChIP-based assays indicate that ABI3 negatively regulates JAZ1 expression by occupying its upstream regulatory sequence and enriching repressive histone modification mark H3K27 trimethylation, thereby occluding RNAPII occupancy. Previous studies have shown that JAZ1 interacts with ABI1, the protein phosphatase 2C, that works during ABA signalling. Our results indicate that in the absence of ABI3, when JAZ1 expression levels are high, the ABI1 protein shows increased stability, compared to when JAZ1 is absent, or ABI3 is overexpressed. Consequently, in the abi3-6 mutant, due to the higher stability of ABI1, reduced phosphorylation of plasma membrane H+-ATPase (AHA2) occurs. HPTS staining further indicated that abi3-6 root cell apoplasts show reduced protonation, compared to wild-type and ABI3 overexpressing seedlings. Such impeded proton extrusion negatively affects cell length in the primary root elongation zone. ABI3 therefore controls cell elongation in the primary root by affecting the ABI1-dependent protonation of root cell apoplasts. In summary, ABI3 controls the expression of JAZ1 and in turn modulates the function of ABI1 to regulate cell length in the elongation zone during primary root growth.

BPMs regulate Arabidopsis seedling development by promoting auxin-independent degradation of the Aux/IAA protein IAA10

After germination, seedlings undergo etiolated development (skotomorphogenesis), enabling them to grow towards the soil surface. In Arabidopsis, etiolated seedlings exhibit rapid hypocotyl elongation, apical hook formation and closed cotyledons to protect the meristem. In this study, we found that high-order mutants in the BPM gene family displayed defects in seedling development, characterized by a shorter hypocotyl, early apical hook opening, and opened cotyledons in the dark. BPM1, BPM2, BPM4, and BPM5 exhibit distinct expression patterns and subcellular localization in etiolated seedlings. In a hypocotyl segment assay the bpm mutants showed defects in auxin response indicating impaired auxin signaling in the hypocotyl. Expression of the auxin reporter DR5:GFP was also altered in the bpm1,4,5 mutant in various tissues compared to the wild type. Furthermore, we showed that BPM1 and IAA10 interact in yeast two-hybrid, BiFC, and Co-IP assays. Experiments in protoplasts indicated that BPM1 promotes ubiquitylation and degradation of IAA10, and the level of IAA10 protein is greater in the bpm1,4,5 mutant. In addition, IAA10 over-expression resulted in phenotypes similar to the bpm mutants. These results indicate that the BPMs target the Aux/IAA proteins for ubiquitylation and degradation. Overall, our findings shed light on the key roles of the BPMs in auxin signaling during seedling development.

Recent Advances in Understanding the Regulatory Mechanism of Plasma Membrane H+-ATPase through the Brassinosteroid Signaling Pathway

The polyhydroxylated steroid phytohormone brassinosteroid (BR) controls many aspects of plant growth, development and responses to environmental changes. Plasma membrane (PM) H+-ATPase, the well-known PM proton pump, is a central regulator in plant physiology, which mediates not only plant growth and development, but also adaptation to stresses. Recent studies highlight that PM H+-ATPase is at least partly regulated via the BR signaling. Firstly, the BR cell surface receptor BRASSINOSTEROID-INSENSITIVE 1 (BRI1) and multiple key components of BR signaling directly or indirectly influence PM H+-ATPase activity. Secondly, the SMALL AUXIN UP RNA (SAUR) gene family physically interacts with BRI1 to enhance organ development of Arabidopsis by activating PM H+-ATPase. Thirdly, RNA-sequencing (RNA-seq) assays showed that the expression of some SAUR genes is upregulated under the light or sucrose conditions, which is related to the phosphorylation state of the penultimate residue of PM H+-ATPase in a time-course manner. In this review, we describe the structural and functional features of PM H+-ATPase and summarize recent progress towards understanding the regulatory mechanism of PM H+-ATPase by BRs, and briefly introduce how PM H+-ATPase activity is modulated by its own biterminal regions and the post-translational modifications.

A CC-NB-ARC-LRR Gene Regulates Bract Morphology in Cotton

Bracts are leaf-like structures in flowering plants. They serve multiple functions such as attracting pollinators, aiding tolerance of abiotic stressors, and conducting photosynthesis. While previous studies extensively examine bract function, the molecular mechanisms underlying bract growth remain unknown. Here, the map-based isolation and characterization of a crucial factor responsible for cotton bract development, identified from a mutant known as frego bract (fg), discovered by Frego in 1945 are presented. This gene, named Ghfg, encodes a CC-NB-ARC-LRR (CNL) family protein. Through analysis of bract form in plants with virus-induced gene silencing (VIGS) and transgenic plants, this gene is confirmed to be the causal gene under the fg locus. Furthermore, high-resolution single-cell transcriptomic landscape of cotton bracts is generated, which reveals differences related to auxin in proliferating cells from TM-1 and T582; differences in auxin distribution and ROS accumulation are experimentally verified. These findings suggest that GhFG is in a self-activated state in the fg mutant, and its activity leads to ROS accumulation that impacts auxin distribution and transport. Finally, an island cotton variety with the frego bract trait is developed, demonstrating a novel solution for reducing the high impurity rate caused by bract remnants.

Cell wall remodeling confers plant architecture with distinct wall structure in Nelumbo nucifera

Lotus (Nelumbo nucifera G.) is a perennial aquatic horticultural plant with diverse architectures. Distinct plant architecture (PA) has certain attractive and practical qualities, but its genetic morphogenesis in lotus remains elusive. In this study, we employ genome-wide association analysis (GWAS) for the seven traits of petiole length (PLL), leaf length (LL), leaf width (LW), peduncle length (PLF), flower diameter (FD), petal length (PeL), and petal width (PeW) in 301 lotus accessions. A total of 90 loci are identified to associate with these traits across 4 years of trials. Meanwhile, we perform RNA sequencing (RNA-seq) to analyze the differential expression of the gene (DEG) transcripts between large and small PA (LPA and SPA) of lotus stems (peduncles and petioles). As a result, eight key candidate genes are identified that are all primarily involved in plant cell wall remodeling significantly associated with PA traits by integrating the results of DEGs and GWAS. To verify this result, we compare the cell wall compositions and structures of LPA versus SPA in representative lotus germplasms. Intriguingly, compared with the SPA lotus, the LPA varieties have higher content of cellulose and hemicellulose, but less filling substrates of pectin and lignin. Additionally, we verified longer cellulose chains and higher cellulose crystallinity with less interference in LPA varieties. Taken together, our study illustrates how plant cell wall remodeling affects PA in lotus, shedding light on the genetic architecture of this significant ornamental trait and offering a priceless genetic resource for future genomic-enabled breeding.

Transcriptome Analysis Deciphers the Underlying Molecular Mechanism of Peanut Lateral Branch Angle Formation Using Erect Branching Mutant

Background The growth habit (GH), also named the branching habit, is an important agronomic trait of peanut and mainly determined by the lateral branch angle (LBA). The branching habit is closely related to peanut mechanized farming, pegging, yield, and disease management. Objectives However, the molecular basis underlying peanut LBA needs to be uncovered. Methods In the present study, an erect branching peanut mutant, eg06g, was obtained via 60Co γ-ray-radiating mutagenesis of a spreading-type peanut cultivar, Georgia-06G (G06G). RNA-seq was performed to compare the transcriptome variation of the upper sides and lower sides of the lateral branch of eg06g and G06G. Results In total, 4908 differentially expressed genes (DEGs) and 5833 DEGs were identified between eg06g and G06G from the lower sides and upper sides of the lateral branch, respectively. GO, KEGG, and clustering enrichment analysis indicated that the carbohydrate metabolic process, cell wall organization or biogenesis, and plant hormone signal transduction were mainly enriched in eg06g. Conclusions Further analysis showed that the genes involved in starch biosynthesis were upregulated in eg06g, which contributed to amyloplast sedimentation and gravity perception. Auxin homeostasis and transport-related genes were found to be upregulated in eg06g, which altered the redistribution of auxin in eg06g and in turn triggered apoplastic acidification and activated cell wall modification-related enzymes, leading to tiller angle establishment through the promotion of cell elongation at the lower side of the lateral branch. In addition, cytokinin and GA also demonstrated synergistic action to finely regulate the formation of peanut lateral branch angles. Collectively, our findings provide new insights into the molecular regulation of peanut LBA and present genetic materials for breeding peanut cultivars with ideotypes.

Indole-3-acetic acid enhances the co-transport of proton and phenanthrene mediated by TaSAUR80-5A in wheat roots

Polycyclic aromatic hydrocarbons (PAHs) are a type of organic pollution that can accumulate in crops and hazard human health. This study used phenanthrene (PHE) as a model PAH and employed hydroponic experiments to illustrate the role of indole-3-acetic acid (IAA) in the regulation of PHE accumulation in wheat roots. At optimal concentrations, wheat roots treated with PHE + IAA showed a 46.9% increase in PHE concentration, whereas treatment with PHE + P-chlorophenoxyisobutyric acid resulted in a 38.77% reduction. Transcriptome analysis identified TaSAUR80-5A as the crucial gene for IAA-enhancing PHE uptake. IAA increases plasma membrane H+-ATPase activity, promoting active transport of PHE via the PHE/H+ cotransport mechanism. These results provide not only the theoretical basis necessary to better understand the function of IAA in PAHs uptake and transport by staple crops, but also a strategy for controlling PAHs accumulation in staple crops and enhancing phytoremediation of PAH-contaminated environments.

Plant Cell Wall Loosening by Expansins

Expansins comprise an ancient group of cell wall proteins ubiquitous in land plants and their algal ancestors. During cell growth, they facilitate passive yielding of the wall's cellulose networks to turgor-generated tensile stresses, without evidence of enzymatic activity. Expansins are also implicated in fruit softening and other developmental processes and in adaptive responses to environmental stresses and pathogens. The major expansin families in plants include α-expansins (EXPAs), which act on cellulose-cellulose junctions, and β-expansins, which can act on xylans. EXPAs mediate acid growth, which contributes to wall enlargement by auxin and other growth agents. The genomes of diverse microbes, including many plant pathogens, also encode expansins designated expansin-like X. Expansins are proposed to disrupt noncovalent bonding between laterally aligned polysaccharides (notably cellulose), facilitating wall loosening for a variety of biological roles.

Alteration in certain growth, biochemical, and anatomical indices of grapevine (Vitis vinifera) in response to the foliar application of auxin under water deficit

Drought-induced stress represents one of the most economically detrimental natural phenomena impacting grapevine (Vitis vinifera ) development, yield, and fruit characteristics. Also, auxin is one of the most important plant growth regulators that can reduce damage caused by stress in plants. In this study, the impact of exogenously sprayed auxin (0, 50, and 200mgL-1 ) on growth, biochemical, and anatomical parameters was investigated in two grapevine varieties (cvs. 'Rashe' and 'Fakhri') under water deficit. According to our findings, water deficit led to a notable decrease in growth, protein content, and anatomical parameters; but significantly enhanced electrolyte leakage. Grapevines exposed to water deficit exhibited substantial increases in total phenolic compounds and antioxidant activity. Applying 50mgL-1 napthalene acetic acid (NAA) reduced the effects of water deficit in both grapevine cultivars by decreasing electrolyte leakage (15% in 'Rashe' and 20% in 'Fakhri'), and accumulating protein content (22% 'Rashe' and 32% 'Fakhri'), total phenolic compounds (33%'Rashe' and 40% 'Fakhri'), and antioxidant capacity (11% 'Rashe' and 39% 'Fakhri'); anantomical parameters were also improved. However, application of 200mgL-1 NAA had adverse effects on growth and biochemical traits of grapevines, with a more pronounced impact on root growth and anatomical parameters compared to other NAA concentrations. In conclusion, the application of 50mgL-1 NAA enhanced grapevine growth, enabling them to better thrive under water deficit.

A microRNA396b-growth regulating factor module controls castor seed size by mediating auxin synthesis

Castor (Ricinus communis L.) is an importance crop cultivated for its oil and economic value. Seed size is a crucial factor that determines crop yield. Gaining insight into the molecular regulatory processes of seed development is essential for the genetic enhancement and molecular breeding of castor. Here, we successfully fine-mapped a major QTL related to seed size, qSS3, to a 180 kb interval on chromosome 03 using F2 populations (DL01×WH11). A 17.6-kb structural variation (SV) was detected through genomic comparison between DL01 and WH11. Analysis of haplotypes showed that the existence of the complete 17.6 kb structural variant may lead to the small seed characteristic in castor. In addition, we found that qSS3 contains the microRNA396b (miR396b) sequence, which is situated within the 17.6 kb SV. The results of our experiment offer additional evidence that miR396-Growth Regulating Factor 4 (GRF4) controls seed size by impacting the growth and multiplication of seed coat and endosperm cells. Furthermore, we found that RcGRF4 activates the expression of YUCCA6 (YUC6), facilitating the production of IAA in seeds and thereby impacting the growth of castor seeds. Our research has discovered a crucial functional module that controls seed size, offering a fresh understanding of the mechanism underlying seed size regulation in castor.

Nitrate Starvation Induces Lateral Root Organogenesis in Triticum aestivum via Auxin Signaling

The lateral root (LR) is an essential component of the plant root system, performing important functions for nutrient and water uptake in plants and playing a pivotal role in cereal crop productivity. Nitrate (NO3-) is an essential nutrient for plants. In this study, wheat plants were grown in 1/2 strength Hoagland's solution containing 5 mM NO3- (check; CK), 0.1 mM NO3- (low NO3-; LN), or 0.1 mM NO3- plus 60 mg/L 2,3,5-triiodobenzoic acid (TIBA) (LNT). The results showed that LN increased the LR number significantly at 48 h after treatment compared with CK, while not increasing the root biomass, and LNT significantly decreased the LR number and root biomass. The transcriptomic analysis showed that LN induced the expression of genes related to root IAA synthesis and transport and cell wall remodeling, and it was suppressed in the LNT conditions. A physiological assay revealed that the LN conditions increased the activity of IAA biosynthesis-related enzymes, the concentrations of tryptophan and IAA, and the activity of cell wall remodeling enzymes in the roots, whereas the content of polysaccharides in the LRP cell wall was significantly decreased compared with the control. Fourier-transform infrared spectroscopy and atomic microscopy revealed that the content of cell wall polysaccharides decreased and the cell wall elasticity of LR primordia (LRP) increased under the LN conditions. The effects of LN on IAA synthesis and polar transport, cell wall remodeling, and LR development were abolished when TIBA was applied. Our findings indicate that NO3- starvation may improve auxin homeostasis and the biological properties of the LRP cell wall and thus promote LR initiation, while TIBA addition dampens the effects of LN on auxin signaling, gene expression, physiological processes, and the root architecture.

PmLBD3 links auxin and brassinosteroid signalling pathways on dwarfism in Prunus mume

BACKGROUND

Grafting with dwarf rootstock is an efficient method to control plant height in fruit production. However, the molecular mechanism remains unclear. Our previous study showed that plants with Prunus mume (mume) rootstock exhibited a considerable reduction in plant height, internode length, and number of nodes compared with Prunus persica (peach) rootstock. The present study aimed to investigate the mechanism behind the regulation of plant height by mume rootstocks through transcriptomic and metabolomic analyses with two grafting combinations, 'Longyan/Mume' and 'Longyan/Peach'.

RESULTS

There was a significant decrease in brassinolide levels in plants that were grafted onto mume rootstocks. Plant hormone signal transduction and brassinolide production metabolism gene expression also changed significantly. Flavonoid levels, amino acid and fatty acid metabolites, and energy metabolism in dwarf plants decreased. There was a notable upregulation of PmLBD3 gene expression in plant specimens that were subjected to grafting onto mume rootstocks. Auxin signalling cues promoted PmARF3 transcription, which directly controlled this upregulation. Through its binding to PmBAS1 and PmSAUR36a gene promoters, PmLBD3 promoted endogenous brassinolide inactivation and inhibited cell proliferation.

CONCLUSIONS

Auxin signalling and brassinolide levels are linked by PmLBD3. Our findings showed that PmLBD3 is a key transcription factor that regulates the balance of hormones through the auxin and brassinolide signalling pathways and causes dwarf plants in stone fruits.

Microneedle electrochemical sensor based on disposable stainless-steel wire for real-time analysis of indole-3-acetic acid and salicylic acid in tomato leaves infected by Pst DC3000 in situ

BACKGROUND

Indole-3-acetic acid (IAA) and salicylic acid (SA), pivotal regulators in plant growth, are integral to a variety of plant physiological activities. The ongoing and simultaneous monitoring of these hormones in vivo enhances our comprehension of their interactive and regulatory roles. Traditional detection methods, such as liquid chromatography-mass spectrometry, cannot obtain precise and immediate information on IAA and SA due to the complexity of sample processing. In contrast, the electrochemical detection method offers high sensitivity, rapid response times, and compactness, making it well-suited for in vivo or real-time detection applications.

RESULTS

A microneedle electrochemical sensor system crafted from disposable stainless steel (SS) wire was specifically designed for the real-time assessment of IAA and SA in plant in situ. This sensor system included a SS wire (100 μm diameter) coated with carbon cement and multi-walled carbon nanotubes, a plain platinum wire (100 μm diameter), and an Ag/AgCl wire (100 μm diameter). Differential pulse voltammetry and amperometry were adopted for detecting SA and IAA within the range of 0.1-20 μM, respectively. This sensor was applied to track IAA and SA fluctuations in tomato leaves during PstDC3000 infection, offering continuous data. Observations indicated an uptick in SA levels following infection, while IAA production was suppressed. The newly developed disposable SS wire-based microneedle electrochemical sensor system is economical, suitable for mass production, and inflicts minimal damage during the monitoring of SA and IAA in plant tissues.

SIGNIFICANCE

This disposable microneedle electrochemical sensor facilitates in vivo detection of IAA and SA in smaller plant tissues and allows for long-time monitoring of their concentrations, which not only propels research into the regulatory and interaction mechanisms of IAA and SA but also furnishes essential tools for advancing precision agriculture.

IAA Synthesis Pathway of Fitibacillus barbaricus WL35 and Its Regulatory Gene Expression Levels in Potato (Solanum tuberosum L.)

Indole-3-acetic acid (IAA), as an important regulator of potato growth, seriously affects the growth and yield of potato. Although many studies have reported that IAA-producing Bacillus can promote plant growth, little research has been conducted on its synthesis pathway and molecular mechanisms. In this study, an IAA-producing strain WL35 was identified as Fitibacillus barbaricus, and its yield was 48.79 mg·L-1. The results of the pot experiments showed that WL35 significantly increased plant height, stem thickness, chlorophyll content, and number of leaves of potato plants by 31.68%, 30.03%, 32.93%, and 36.59%, respectively. In addition, in the field experiments, WL35-treated plants increased commercial potato yield by 16.45%, vitamin C content by 16.35%, protein content by 75%, starch content by 6.60%, and the nitrogen, phosphorus, and potassium accumulation by 9.98%, 12.70%, and 26.76%, respectively. Meanwhile, the synthetic pathway of WL35 was found to be dominated by the tryptophan-dependent pathway, the IAM, TAM, and IPA pathways worked together, and the pathways that played a role at different times were different. Furthermore, RNA-seq analysis showed that there were a total of 2875 DEGs regulated in the samples treated with WL35 seed dressing compared with the CK, of which 1458 genes were up-regulated and 1417 genes were down-regulated. Potato roots express differential genes enriched in processes such as carbohydrate metabolism processes and cellular polysaccharide metabolism, which regulate potato plant growth and development. The above results provide a theoretical basis for the further exploration of the synthesis pathway of IAA and its growth-promoting mechanism in potato.

An integrated QTL and RNA-seq analysis revealed new petal morphology loci in Brassica napus L

BACKGROUND

Rapeseed (Brassica napus L.) is one of the most important oil crops and a wildly cultivated horticultural crop. The petals of B. napus serve to protect the reproductive organs and attract pollinators and tourists. Understanding the genetic basis of petal morphology regulation is necessary for B. napus breeding.

RESULTS

In the present study, the quantitative trait locus (QTL) analysis for six B. napus petal morphology parameters in a double haploid (DH) population was conducted across six microenvironments. A total of 243 QTLs and five QTL hotspots were observed, including 232 novel QTLs and three novel QTL hotspots. The spatiotemporal transcriptomic analysis of the diversiform petals was also conducted, which indicated that the expression of plant hormone metabolic and cytoskeletal binding protein genes was variant among diversiform petals.

CONCLUSIONS

The integration of QTL and RNA-seq analysis revealed that plant hormones (including cytokinin, auxin, and gibberellin) and cytoskeleton were key regulators of the petal morphology. Subsequently, 61 high-confidence candidate genes of petal morphology regulation were identified, including Bn.SAUR10, Bn.ARF18, Bn.KIR1, Bn.NGA2, Bn.PRF1, and Bn.VLN4. The current study provided novel QTLs and candidate genes for further breeding B. napus varieties with diversiform petals.

Formation mechanism and regulation analysis of trumpet leaf in Ginkgo biloba L

Introduction

The research on plant leaf morphology is of great significance for understanding the development and evolution of plant organ morphology. As a relict plant, the G. biloba leaf morphology typically exhibits bifoliate and peltate forms. However, throughout its long evolutionary history, Ginkgo leaves have undergone diverse changes.

Methods

This study focuses on the distinct "trumpet" leaves and normal fan-shaped leaves of G. biloba for analysis of their phenotypes, photosynthetic activity, anatomical observations, as well as transcriptomic and metabolomic analyses.

Results

The results showed that trumpet-shaped G. biloba leaves have fewer cells, significant morphological differences between dorsal and abaxial epidermal cells, leading to a significantly lower net photosynthetic rate. Additionally, this study found that endogenous plant hormones such as GA, auxin, and JA as well as metabolites such as flavonoids and phenolic acids play roles in the formation of trumpet-shaped G. biloba leaves. Moreover, the experiments revealed the regulatory mechanisms of various key biological processes and gene expressions in the trumpet-shaped leaves of G. biloba.

Discussion

Differences in the dorsal and abdominal cells of G. biloba leaves can cause the leaf to curl, thus reducing the overall photosynthetic efficiency of the leaves. However, the morphology of plant leaves is determined during the primordia leaf stage. In the early stages of leaf development, the shoot apical meristem (SAM) determines the developmental morphology of dicotyledonous plant leaves. This process involves the activity of multiple gene families and small RNAs. The establishment of leaf morphology is complexly regulated by various endogenous hormones, including the effect of auxin on cell walls. Additionally, changes in intracellular ion concentrations, such as fluctuations in Ca2+ concentration, also affect cell wall rigidity, thereby influencing leaf growth morphology.

Crosstalk between Rho of Plants GTPase signalling and plant hormones

Rho of Plants (ROPs) constitute a plant-specific subset of small guanine nucleotide-binding proteins within the Cdc42/Rho/Rac family. These versatile proteins regulate diverse cellular processes, including cell growth, cell division, cell morphogenesis, organ development, and stress responses. In recent years, the dynamic cellular and subcellular behaviours orchestrated by ROPs have unveiled a notable connection to hormone-mediated organ development and physiological responses, thereby expanding our knowledge of the functions and regulatory mechanisms of this signalling pathway. This review delineates advancements in understanding the interplay between plant hormones and the ROP signalling cascade, focusing primarily on the connections with auxin and abscisic acid pathways, alongside preliminary discoveries in cytokinin, brassinosteroid, and salicylic acid responses. It endeavours to shed light on the intricate, coordinated mechanisms bridging cell- and tissue-level signals that underlie plant cell behaviour, organ development, and physiological processes, and highlights future research prospects and challenges in this rapidly developing field.

GmHXK2 promotes the salt tolerance of soybean seedlings by mediating AsA synthesis, and auxin synthesis and distribution

BACKGROUND

Salt is an important factor that affects crop productivity. Plant hexokinases (HXKs) are key enzymes in the glycolytic pathway and sugar signaling transduction pathways of plants. In previous studies, we identified and confirmed the roles of GmHXK2 in salt tolerance.

RESULTS

In this study, we analyzed the tissue-specific expression of GmHXK2 at different growth stages throughout the plant's life cycle. The results showed that GmHXK2 was expressed significantly in all tissues at vegetative stages, including germination and seedling. However, no expression was detected in the pods, and there was little expression in flowers during the later mature period. Arabidopsis plants overexpressing the GmHXK2 (OE) had more lateral roots. The OE seedlings also produced higher levels of auxin and ascorbic acid (AsA). Additionally, the expression levels of genes PMM, YUC4/YUC6/YUC8, and PIN/LAX1,LAX3, which are involved respectively in the synthesis of AsA and auxin, as well as polar auxin transport, were upregulated in OE plants. This upregulation occurred specifically under exogenous glucose treatment. AtHKT1, AtSOS1, and AtNHX1 were up-regulated in OE plants under salt stress, suggesting that GmHXK2 may modulate salt tolerance by maintaining ion balance within the cells and alleviating damage caused by salt stress. Additionally, we further confirmed the interaction between GmHXK2 and the protein GmPMM through yeast two-hybridization and bimolecular fluorescence complementation assays, respectively.

CONCLUSION

The expression of GmHXK2 gene in plants is organ-specific and developmental stage specific. GmHXK2 not only regulates the synthesis of AsA and the synthesis and distribution of auxin, but also promotes root elongation and induces lateral root formation, potentially enhancing soil water absorption. This study reveals the crosstalk between sugar signaling and hormone signaling in plants, where GmHXK2 acts as a glucose sensor through its interaction with GmPMM, and sheds light on the molecular mechanism by which GmHXK2 gene is involved in salt tolerance in plants.

Physiological and transcriptome analysis of changes in endogenous hormone and sugar content during the formation of tender asparagus stems

Asparagus is a nutritionally dense stem vegetable whose growth and development are correlated with its quality and yield. To investigate the dynamic changes and underlying mechanisms during the elongation and growth process of asparagus stems, we documented the growth pattern of asparagus and selected stem segments from four consecutive elongation stages using physiological and transcriptome analyses. Notably, the growth rate of asparagus accelerated at a length of 25 cm. A significant decrease in the concentration of sucrose, fructose, glucose, and additional sugars was observed in the elongation region of tender stems. Conversely, the levels of auxin and gibberellins(GAs) were elevated along with increased activity of enzymes involved in sucrose degradation. A significant positive correlation existed between auxin, GAs, and enzymes involved in sucrose degradation. The ABA content gradually increased with stem elongation. The tissue section showed that cell elongation is an inherent manifestation of stem elongation. The differential genes screened by transcriptome analysis were enriched in pathways such as starch and sucrose metabolism, phytohormone synthesis metabolism, and signal transduction. The expression levels of genes such as ARF, GA20ox, NCED, PIF4, and otherswere upregulated during stem elongation, while DAO, GA2ox, and other genes were downregulated. The gene expression level was consistent with changes in hormone content and influenced the cell length elongation. Additionally, the expression results of RT-qPCR were consistent with RNA-seq. The observed variations in gene expression levels, endogenous hormones and sugar changes during the elongation and growth of asparagus tender stems offer valuable insights for future investigations into the molecular mechanisms of asparagus stem growth and development and provide a theoretical foundation for cultivation and production practices.

A Small Auxin-Up RNA Gene, IbSAUR36, Regulates Adventitious Root Development in Transgenic Sweet Potato

Small auxin-upregulated RNAs (SAURs), as the largest family of early auxin-responsive genes, play important roles in plant growth and development processes, such as auxin signaling and transport, hypocotyl development, and tolerance to environmental stresses. However, the functions of few SAUR genes are known in the root development of sweet potatoes. In this study, an IbSAUR36 gene was cloned and functionally analyzed. The IbSAUR36 protein was localized to the nucleus and plasma membrane. The transcriptional level of this gene was significantly higher in the pencil root and leaf.This gene was strongly induced by indole-3-acetic acid (IAA), but it was downregulated under methyl-jasmonate(MeJA) treatment. The promoter of IbSAUR36 contained the core cis-elements for phytohormone responsiveness. Promoter β-glucuronidase (GUS) analysis in Arabidopsis showed that IbSAUR36 is highly expressed in the young tissues of plants, such as young leaves, roots, and buds. IbSAUR36-overexpressing sweet potato roots were obtained by an efficient Agrobacterium rhizogenes-mediated root transgenic system. We demonstrated that overexpression of IbSAUR36 promoted the accumulation of IAA, upregulated the genes encoding IAA synthesis and its signaling pathways, and downregulated the genes encoding lignin synthesis and JA signaling pathways. Taken together, these results show that IbSAUR36 plays an important role in adventitious root (AR) development by regulating IAA signaling, lignin synthesis, and JA signaling pathways in transgenic sweet potatoes.

Small but powerful: RALF peptides in plant adaptive and developmental responses

Plants live in a highly dynamic environment and require to rapidly respond to a plethora of environmental stimuli, so that to maintain their optimal growth and development. A small plant peptide, rapid alkalization factor (RALF), can rapidly increase the pH value of the extracellular matrix in plant cells. RALFs always function with its corresponding receptors. Mechanistically, effective amount of RALF is induced and released at the critical period of plant growth and development or under different external environmental factors. Recent studies also highlighted the role of RALF peptides as important regulators in plant intercellular communications, as well as their operation in signal perception and as ligands for different receptor kinases on the surface of the plasma membrane, to integrate various environmental cues. In this context, understanding the fine-print of above processes may be essential to solve the problems of crop adaptation to various harsh environments under current climate trends scenarios, by genetic means. This paper summarizes the current knowledge about the structure and diversity of RALF peptides and their roles in plant development and response to stresses, highlighting unanswered questions and problems to be solved.

Defying gravity: WEEP promotes negative gravitropism in peach trees by establishing asymmetric auxin gradients

Trees with weeping shoot architectures are valued for their beauty and are a resource for understanding how plants regulate posture control. The peach (Prunus persica) weeping phenotype, which has elliptical downward arching branches, is caused by a homozygous mutation in the WEEP gene. Little is known about the function of WEEP despite its high conservation throughout Plantae. Here, we present the results of anatomical, biochemical, biomechanical, physiological, and molecular experiments that provide insight into WEEP function. Our data suggest that weeping peach trees do not have defects in branch structure. Rather, transcriptomes from the adaxial (upper) and abaxial (lower) sides of standard and weeping branch shoot tips revealed flipped expression patterns for genes associated with early auxin response, tissue patterning, cell elongation, and tension wood development. This suggests that WEEP promotes polar auxin transport toward the lower side during shoot gravitropic response, leading to cell elongation and tension wood development. In addition, weeping peach trees exhibited steeper root systems and faster lateral root gravitropic response. This suggests that WEEP moderates root gravitropism and is essential to establishing the set-point angle of lateral roots from the gravity vector. Additionally, size exclusion chromatography indicated that WEEP proteins self-oligomerize, like other proteins with sterile alpha motif domains. Collectively, our results from weeping peach provide insight into polar auxin transport mechanisms associated with gravitropism and lateral shoot and root orientation.

Genome-Wide Analysis of the SAUR Gene Family and Its Expression Profiles in Response to Salt Stress in Santalum album

The SAUR (small auxin-up RNA) family constitutes a category of genes that promptly respond to the hormone auxin and play a pivotal role in diverse biological processes encompassing plant growth and the response to abiotic stress. Santalum album L., a semi-parasitic evergreen tree, is renowned for its economically valuable essential oils, positioning it among the most prized tree species. In this study, a meticulous identification and comprehensive analysis of 43 SAUR genes was conducted within S. album. Based on phylogenetic relationships, the SaSAUR genes were systematically categorized into five groups. A collinearity analysis revealed intriguing insights, disclosing 14 segmental duplications and 9 tandem duplications within the SaSAUR genes, emphasizing the pivotal role of duplication in the expansion of this gene family. Noteworthy variations in the expression levels of SaSAUR genes were observed by delving into the SaSAUR transcriptome data from various tissues, including leaves, roots, and heartwood, as well as under salt-stress conditions. Notably, SaSAUR08 and SaSAUR13 were significantly upregulated in heartwood compared with roots and leaves, while SaSAUR18 was markedly more expressed in roots compared with heartwood and leaves. Furthermore, SaSAUR27 and SaSAUR28 were found to respond closely to salt stress, hinting at their potential involvement in the salt-stress response mechanism. This research offers a comprehensive investigation of SAUR genes in S. album and establishes a foundation for future exploration of the SAUR gene family, particularly its relation to growth and salt-stress responses.

The plant cell wall-dynamic, strong, and adaptable-is a natural shapeshifter

Mythology is replete with good and evil shapeshifters, who, by definition, display great adaptability and assume many different forms-with several even turning themselves into trees. Cell walls certainly fit this definition as they can undergo subtle or dramatic changes in structure, assume many shapes, and perform many functions. In this review, we cover the evolution of knowledge of the structures, biosynthesis, and functions of the 5 major cell wall polymer types that range from deceptively simple to fiendishly complex. Along the way, we recognize some of the colorful historical figures who shaped cell wall research over the past 100 years. The shapeshifter analogy emerges more clearly as we examine the evolving proposals for how cell walls are constructed to allow growth while remaining strong, the complex signaling involved in maintaining cell wall integrity and defense against disease, and the ways cell walls adapt as they progress from birth, through growth to maturation, and in the end, often function long after cell death. We predict the next century of progress will include deciphering cell type-specific wall polymers; regulation at all levels of polymer production, crosslinks, and architecture; and how walls respond to developmental and environmental signals to drive plant success in diverse environments.

Structure and growth of plant cell walls

Plant cells build nanofibrillar walls that are central to plant growth, morphogenesis and mechanics. Starting from simple sugars, three groups of polysaccharides, namely, cellulose, hemicelluloses and pectins, with very different physical properties are assembled by the cell to make a strong yet extensible wall. This Review describes the physics of wall growth and its regulation by cellular processes such as cellulose production by cellulose synthase, modulation of wall pH by plasma membrane H+-ATPase, wall loosening by expansin and signalling by plant hormones such as auxin and brassinosteroid. In addition, this Review discusses the nuanced roles, properties and interactions of cellulose, matrix polysaccharides and cell wall proteins and describes how wall stress and wall loosening cooperatively result in cell wall growth.

An auxin research odyssey: 1989-2023

The phytohormone auxin is at times called the master regulator of plant processes and has been shown to be a central player in embryo development, the establishment of the polar axis, early aspects of seedling growth, as well as growth and organ formation during later stages of plant development. The Plant Cell has been key, since the inception of the journal, to developing an understanding of auxin biology. Auxin-regulated plant growth control is accomplished by both changes in the levels of active hormones and the sensitivity of plant tissues to these concentration changes. In this historical review, we chart auxin research as it has progressed in key areas and highlight the role The Plant Cell played in these scientific developments. We focus on understanding auxin-responsive genes, transcription factors, reporter constructs, perception, and signal transduction processes. Auxin metabolism is discussed from the development of tryptophan auxotrophic mutants, the molecular biology of conjugate formation and hydrolysis, indole-3-butyric acid metabolism and transport, and key steps in indole-3-acetic acid biosynthesis, catabolism, and transport. This progress leads to an expectation of a more comprehensive understanding of the systems biology of auxin and the spatial and temporal regulation of cellular growth and development.

WAV E3 ubiquitin ligases mediate degradation of IAA32/34 in the TMK1-mediated auxin signaling pathway during apical hook development

Auxin regulates plant growth and development through downstream signaling pathways, including the best-known SCFTIR1/AFB-Aux/IAA-ARF pathway and several other less characterized "noncanonical" pathways. Recently, one SCFTIR1/AFB-independent noncanonical pathway, mediated by Transmembrane Kinase 1 (TMK1), was discovered through the analyses of its functions in Arabidopsis apical hook development. Asymmetric accumulation of auxin on the concave side of the apical hook triggers DAR1-catalyzed release of the C-terminal of TMK1, which migrates into the nucleus, where it phosphorylates and stabilizes IAA32/34 to inhibit cell elongation, which is essential for full apical hook formation. However, the molecular factors mediating IAA32/34 degradation have not been identified. Here, we show that proteins in the CYTOKININ INDUCED ROOT WAVING 1 (CKRW1)/WAVY GROWTH 3 (WAV3) subfamily act as E3 ubiquitin ligases to target IAA32/34 for ubiquitination and degradation, which is inhibited by TMK1c-mediated phosphorylation. This antagonistic interaction between TMK1c and CKRW1/WAV3 subfamily E3 ubiquitin ligases regulates IAA32/34 levels to control differential cell elongation along opposite sides of the apical hook.

Genome-wide identification and expression analysis of ARF gene family in embryonic development of Korean pine (Pinus koraiensis)

BACKGROUND

The Auxin Responsive Factor (ARF) family plays a crucial role in mediating auxin signal transduction and is vital for plant growth and development. However, the function of ARF genes in Korean pine (Pinus koraiensis), a conifer species of significant economic value, remains unclear.

RESULTS

This study utilized the whole genome of Korean pine to conduct bioinformatics analysis, resulting in the identification of 13 ARF genes. A phylogenetic analysis revealed that these 13 PkorARF genes can be classified into 4 subfamilies, indicating the presence of conserved structural characteristics within each subfamily. Protein interaction prediction indicated that Pkor01G00962.1 and Pkor07G00704.1 may have a significant role in regulating plant growth and development as core components of the PkorARFs family. Additionally, the analysis of RNA-seq and RT-qPCR expression patterns suggested that PkorARF genes play a crucial role in the development process of Korean pine.

CONCLUSION

Pkor01G00962.1 and Pkor07G00704.1, which are core genes of the PkorARFs family, play a potentially crucial role in regulating the fertilization and developmental process of Korean pine. This study provides a valuable reference for investigating the molecular mechanism of embryonic development in Korean pine and establishes a foundation for cultivating high-quality Korean pine.

Role of Plant-Growth-Promoting Rhizobacteria in Plant Machinery for Soil Heavy Metal Detoxification

Heavy metals migrate easily and are difficult to degrade in the soil environment, which causes serious harm to the ecological environment and human health. Thus, soil heavy metal pollution has become one of the main environmental issues of global concern. Plant-growth-promoting rhizobacteria (PGPR) is a kind of microorganism that grows around the rhizosphere and can promote plant growth and increase crop yield. PGPR can change the bioavailability of heavy metals in the rhizosphere microenvironment, increase heavy metal uptake by phytoremediation plants, and enhance the phytoremediation efficiency of heavy-metal-contaminated soils. In recent years, the number of studies on the phytoremediation efficiency of heavy-metal-contaminated soil enhanced by PGPR has increased rapidly. This paper systematically reviews the mechanisms of PGPR that promote plant growth (including nitrogen fixation, phosphorus solubilization, potassium solubilization, iron solubilization, and plant hormone secretion) and the mechanisms of PGPR that enhance plant-heavy metal interactions (including chelation, the induction of systemic resistance, and the improvement of bioavailability). Future research on PGPR should address the challenges in heavy metal removal by PGPR-assisted phytoremediation.

The ldp1 Mutation Affects the Expression of Auxin-Related Genes and Enhances SAM Size in Rice

Panicle type is one of the important factors affecting rice (Oryza sativa L.) yield, and the identification of regulatory genes in panicle development can provide significant insights into the molecular network involved. This study identified a large and dense panicle 1 (ldp1) mutant produced from the Wuyunjing 7 (WYJ7) genotype, which displayed significant relative increases in panicle length, number of primary and secondary branches, number of grains per panicle, grain width, and grain yield per plant. Scanning electron microscopy results showed that the shoot apical meristem (SAM) of ldp1 was relatively larger at the bract stage (BM), with a significantly increased number of primary (PBM) and secondary branch (SBM) meristematic centers, indicating that the ldp1 mutation affects early stages in SAM development Comparative RNA-Seq analysis of meristem tissues from WYJ7 and ldp1 at the BM, PBM, and SBM developmental stages indicated that the number of differentially expressed genes (DEGs) were highest (1407) during the BM stage. Weighted gene coexpression network analysis (WGCNA) revealed that genes in one module (turquoise) are associated with the ldp1 phenotype and highly expressed during the BM stage, suggesting their roles in the identity transition and branch differentiation stages of rice inflorescences. Hub genes involved in auxin synthesis and transport pathways, such as OsAUX1, OsAUX4, and OsSAUR25, were identified. Moreover, GO and KEGG analysis of the DEGs in the turquoise module and the 1407 DEGs in the BM stage revealed that a majority of genes involved in tryptophan metabolism and auxin signaling pathway were differentially expressed between WYJ and ldp1. The genetic analysis indicated that the ldp1 phenotype is controlled by a recessive monogene (LDP1), which was mapped to a region between 16.9 and 18.1 Mb on chromosome seven. This study suggests that the ldp1 mutation may affect the expression of key genes in auxin synthesis and signal transduction, enhance the size of SAM, and thus affect panicle development. This study provides insights into the molecular regulatory network underlying rice panicle morphogenesis and lays an important foundation for further understanding the function and molecular mechanism of LDP1 during panicle development.

Protein post-translational modifications in auxin signaling

Protein post-translational modifications (PTMs), such as ubiquitination, phosphorylation, and small ubiquitin-like modifier (SUMO)ylation, are crucial for regulating protein stability, activity, subcellular localization, and binding with cofactors. Such modifications remarkably increase the variety and complexity of proteomes, which are essential for regulating numerous cellular and physiological processes. The regulation of auxin signaling is finely tuned in time and space to guide various plant growth and development. Accumulating evidence indicates that PTMs play critical roles in auxin signaling regulations. Thus, a thorough and systematic review of the functions of PTMs in auxin signal transduction will improve our profound comprehension of the regulation mechanism of auxin signaling and auxin-mediated various processes. This review discusses the progress of protein ubiquitination, phosphorylation, histone acetylation and methylation, SUMOylation, and S-nitrosylation in the regulation of auxin signaling.

The roles of DNA methylation on pH dependent i-motif (iM) formation in rice

I-motifs (iMs) are four-stranded non-B DNA structures containing C-rich DNA sequences. The formation of iMs is sensitive to pH conditions and DNA methylation, although the extent of which is still unknown in both humans and plants. To investigate this, we here conducted iMab antibody-based immunoprecipitation and sequencing (iM-IP-seq) along with bisulfite sequencing using CK (original genomic DNA without methylation-related treatments) and hypermethylated or demethylated DNA at both pH 5.5 and 7.0 in rice, establishing a link between pH, DNA methylation and iM formation on a genome-wide scale. We found that iMs folded at pH 7.0 displayed higher methylation levels than those formed at pH 5.5. DNA demethylation and hypermethylation differently influenced iM formation at pH 7.0 and 5.5. Importantly, CG hypo-DMRs (differentially methylated regions) and CHH (H = A, C and T) hyper-DMRs alone or coordinated with CG/CHG hyper-DMRs may play determinant roles in the regulation of pH dependent iM formation. Thus, our study shows that the nature of DNA sequences alone or combined with their methylation status plays critical roles in determining pH-dependent formation of iMs. It therefore deepens the understanding of the pH and methylation dependent modulation of iM formation, which has important biological implications and practical applications.

Auxin exposure disrupts feeding behavior and fatty acid metabolism in adult Drosophila

The ease of genetic manipulation in Drosophila melanogaster using the Gal4/UAS system has been beneficial in addressing key biological questions. Current modifications of this methodology to temporally induce transgene expression require temperature changes or exposure to exogenous compounds, both of which have been shown to have detrimental effects on physiological processes. The recently described auxin-inducible gene expression system (AGES) utilizes the plant hormone auxin to induce transgene expression and is proposed to be the least toxic compound for genetic manipulation, with no obvious effects on Drosophila development and survival in one wild-type strain. Here, we show that auxin delays larval development in another widely used fly strain, and that short- and long-term auxin exposure in adult Drosophila induces observable changes in physiology and feeding behavior. We further reveal a dosage response to adult survival upon auxin exposure, and that the recommended auxin concentration for AGES alters feeding activity. Furthermore, auxin-fed male and female flies exhibit a significant decrease in triglyceride levels and display altered transcription of fatty acid metabolism genes. Although fatty acid metabolism is disrupted, auxin does not significantly impact adult female fecundity or progeny survival, suggesting AGES may be an ideal methodology for studying limited biological processes. These results emphasize that experiments using temporal binary systems must be carefully designed and controlled to avoid confounding effects and misinterpretation of results.

RAF-like protein kinases mediate a deeply conserved, rapid auxin response

The plant-signaling molecule auxin triggers fast and slow cellular responses across land plants and algae. The nuclear auxin pathway mediates gene expression and controls growth and development in land plants, but this pathway is absent from algal sister groups. Several components of rapid responses have been identified in Arabidopsis, but it is unknown if these are part of a conserved mechanism. We recently identified a fast, proteome-wide phosphorylation response to auxin. Here, we show that this response occurs across 5 land plant and algal species and converges on a core group of shared targets. We found conserved rapid physiological responses to auxin in the same species and identified rapidly accelerated fibrosarcoma (RAF)-like protein kinases as central mediators of auxin-triggered phosphorylation across species. Genetic analysis connects this kinase to both auxin-triggered protein phosphorylation and rapid cellular response, thus identifying an ancient mechanism for fast auxin responses in the green lineage.

Ultraviolet-A1 radiation induced a more favorable light-intercepting leaf-area display than blue light and promoted plant growth

Plants adjust their morphology in response to light environment by sensing an array of light cues. Though the wavelengths of ultraviolet-A1 radiation (UV-A1, 350-400 nm) are close to blue light (B, 400-500 nm) and share same flavoprotein photoreceptors, it remains poorly understood how plant responses to UV-A1 radiation could differ from those to B. We initially grown tomato plants under monochromatic red light (R, 660 nm) as control, subsequently transferred them to four dichromatic light treatments containing ~20 µmol m-2  s-1 of UV-A1 radiation, peaking at 370 nm (UV-A370 ) or 400 nm (V400 ), or B (450 nm, at ~20 or 1.5 µmol m-2  s-1 ), with same total photon irradiance (~200 μmol m-2  s-1 ). We show that UV-A370 radiation was the most effective in inducing light-intercepting leaf-area display formation, resulting in larger leaf area and more shoot biomass, while it triggered weaker and later transcriptome-wide responses than B. Mechanistically, UV-A370 -promoted leaf-area display response was apparent in less than 12 h and appeared as very weakly related to transcriptome level regulation, which likely depended on the auxin transportation and cell wall acidification. This study revealed wavelength-specific responses within UV-A/blue region challenging usual assumptions that the role of UV-A1 radiation function similarly as blue light in mediating plant processes.

Biological control of potato common scab and growth promotion of potato by Bacillus velezensis Y6

Potato common scab, caused mainly by Streptomyces scabies, causes surface necrosis and reduces the economic value of potato tubers, but effective chemical control is still lacking. In this study, an attempt was made to control potato common scab by inoculating potatoes with Bacillus velezensis (B. velezensis) and to further investigate the mechanism of biological control. The results showed that B. velezensis Y6 could reduce the disease severity of potato common scab from 49.92 ± 25.74% [inoculated with Streptomyces scabies (S. scabies) only] to 5.56 ± 1.89% (inoculated with S. scabies and Y6 on the same day) and increase the potato yield by 37.32% compared with the control under pot experiment in this study. Moreover, in the field trial, it was found that Y6 could also significantly reduce disease severity from 13.20 ± 1.00% to 4.00 ± 0.70% and increase the potato yield from 2.07 ± 0.10 ton/mu to 2.87 ± 0.28 ton/mu (p < 0.01; Tukey's test). Furthermore, RNA-seq analysis indicated that 256 potato genes were upregulated and 183 potato genes were downregulated in response to B. velezensis Y6 inoculation. In addition, strain Y6 was found to induce the expression of plant growth-related genes in potato, including cell wall organization, biogenesis, brassinosteroid biosynthesis, and plant hormone transduction genes, by 1.01-4.29 times. As well as up-regulate hydroquinone metabolism-related genes and several transcription factors (bHLH, MYB, and NAC) by 1.13-4.21 times. In summary, our study will help to understand the molecular mechanism of biological control of potato common scab and improve potato yield.

ABLs and TMKs are co-receptors for extracellular auxin

Extracellular perception of auxin, an essential phytohormone in plants, has been debated for decades. Auxin-binding protein 1 (ABP1) physically interacts with quintessential transmembrane kinases (TMKs) and was proposed to act as an extracellular auxin receptor, but its role was disputed because abp1 knockout mutants lack obvious morphological phenotypes. Here, we identified two new auxin-binding proteins, ABL1 and ABL2, that are localized to the apoplast and directly interact with the extracellular domain of TMKs in an auxin-dependent manner. Furthermore, functionally redundant ABL1 and ABL2 genetically interact with TMKs and exhibit functions that overlap with those of ABP1 as well as being independent of ABP1. Importantly, the extracellular domain of TMK1 itself binds auxin and synergizes with either ABP1 or ABL1 in auxin binding. Thus, our findings discovered auxin receptors ABL1 and ABL2 having functions overlapping with but distinct from ABP1 and acting together with TMKs as co-receptors for extracellular auxin.

Auxin Exposure Disrupts Feeding Behavior and Fatty Acid Metabolism in Adult Drosophila

The ease of genetic manipulation in Drosophila melanogaster using the Gal4/UAS system has been beneficial in addressing key biological questions. Current modifications of this methodology to temporally induce transgene expression require temperature changes or exposure to exogenous compounds, both of which have been shown to have detrimental effects on physiological processes. The recently described auxin-inducible gene expression system (AGES) utilizes the plant hormone auxin to induce transgene expression and is proposed to be the least toxic compound for genetic manipulation, with no obvious effects on Drosophila development and survival in one wild-type strain. Here we show that auxin delays larval development in another widely-used fly strain, and that short- and long-term auxin exposure in adult Drosophila induces observable changes in physiology and feeding behavior. We further reveal a dosage response to adult survival upon auxin exposure, and that the recommended auxin concentration for AGES alters feeding activity. Furthermore, auxin fed male and female flies exhibit a significant decrease in triglyceride levels and display altered transcription of fatty acid metabolism genes. Although fatty acid metabolism is disrupted, auxin does not significantly impact adult female fecundity or progeny survival, suggesting AGES may be an ideal methodology for studying limited biological processes. These results emphasize that experiments using temporal binary systems must be carefully designed and controlled to avoid confounding effects and misinterpretation of results.

Highly sensitive analysis of photoregulation and dynamic distribution of phytohormones based on nanoconfined liquid phase nanoextraction

BACKGROUND

As a vital energy source, light is one of the most significant environmental signals for plants' growth and development. The crosstalk amongst phytohormones regulated by light exhibits quantitative dynamic changes, but methodologies to analyze their distribution during plant growth are still limited. Rapid, highly sensitive, low-invasive detection and simultaneous assessment of the levels of multiple classes of phytohormones have important phytology applications, however the existing sample pretreatment strategies remain intricate, laborious, and far from being developed for in vivo high-sensitivity testing. (81) RESULTS: We applied a nanoconfined liquid phase nanoextraction (NLPNE) technique based on acidified carbon nanofibers (ACNFs) in combination with LC-ESI-MS/MS for highly sensitive analysis of acidic phytohormones' photoregulation and dynamic distribution. In this system, the mass transfer ability of analytes entering the nanoconfined space is significantly improved given the nanoconfined effect. In particular, the accelerated and strong adsorption of alkaline compounds to the ACNFs surface provide minimum interference for acidic compounds (photosensitive phytohormones), which facilitates their simple, fast, and selective quantification with improved sensitivity. The ACNFs-NLPNE strategy achieved quantitative enrichment of multi-class phytohormones in less than 5 min, and detection limits down to 0.49 fg mL-1. Moreover, we monitored the phytohormone changes under red and blue monochromatic light with relative standard deviations <13.4 %. The results further indicated that short-time red light regulation promoted Lepidium sativum L. growth while blue light inhibited it. (141) SIGNIFICANCE: A nanoconfinement effect-based sample pretreatment platform was developed for monitoring photoregulation phytohormones dynamic distribution with higher sensitivity and stability. Our findings highlighted the importance of the NLPNE approach in providing an accurate plant crosstalk information at the molecular level, which opens a promising avenue for investigating internal hormonal responses to external stimuli. (52).

Comparative Transcriptome Sequencing and Endogenous Phytohormone Content of Annual Grafted Branches of Zelkova schneideriana and Its Dwarf Variety HenTianGao

Zelkova schneideriana is a fast-growing tree species endemic to China. Recent surveys and reports have highlighted a continued decline in its natural populations; therefore, it is included in the Red List of Threatened Species by The International Union for Conservation of Nature. A new variety "HenTianGao" (H) has been developed with smaller plant height, slow growth, and lower branching points. In this study, we attempted to understand the differences in plant height of Z. schneideriana (J) and its dwarf variety H. We determined the endogenous hormone content in the annual grafted branches of both J and H. J exhibited higher gibberellic acid (GA)-19 and trans-Zeatin (tZ) levels, whereas H had higher levels of indole-3-acetic acid (IAA) catabolite 2-oxindole-3-acetic acid (OxIAA), IAA-Glu conjugate, and jasmonic acid (JA) (and its conjugate JA-Ile). The transcriptome comparison showed differential regulation of 20,944 genes enriched in growth and development, signaling, and metabolism-related pathways. The results show that the differential phytohormone level (IAA, JA, tZ, and GA) was consistent with the expression of the genes associated with their biosynthesis. The differences in relative OxIAA, IAA-Glu, GA19, trans-Zeatin, JA, and JA-Ile levels were linked to changes in respective signaling-related genes. We also observed significant differences in the expression of cell size, number, proliferation, cell wall biosynthesis, and remodeling-related genes in J and H. The differences in relative endogenous hormone levels, expression of biosynthesis, and signaling genes provide a theoretical basis for understanding the plant height differences in Z. schneideriana.

Transcriptome analysis reveals the effect of acidic environment on adventitious root differentiation in Camellia sinensis

The generation of adventitious roots (ARs) is the key to the success of cuttings. The appropriate environment for AR differentiation in tea plants is acidic. However, the mechanism is unclear. In this study, pH 4.5 was suitable condition for the differentiation of AR in tea plants. At the base of cuttings, the root primordia differentiated ARs more rapidly at pH 4.5 than pH 7.0, and nine AR differentiation-related genes were found to be differentially expressed in 30 days, the result was also validated by qRT-PCR. The promoter regions of these genes contained auxin and brassinosteroid response elements. The expression levels of several genes which were involved in auxin and brassinosteroid synthesis as well as signaling at pH 4.5 compared to pH 7.0 occurred differential expression. Brassinolide (BL) and indole-3-acetic acid (IAA) could affect the differentiation of ARs under pH 4.5 and pH 7.0. By qRT-PCR analysis of genes during ARs generation, BL and IAA inhibited and promoted the expression of CsIAA14 gene, respectively, to regulate auxin signal transduction. Meanwhile, the expression levels of CsKNAT4, CsNAC2, CsNAC100, CsWRKY30 and CsLBD18 genes were up-regulated upon auxin treatment and were positively correlated with ARs differentiation.This study showed that pH 4.5 was the most suitable environment for the root primordia differentiation of AR in tea plant. Proper acidic pH conditions promoted auxin synthesis and signal transduction. The auxin initiated the expression of AR differentiation-related genes, and promoted its differentiated. BL was involved in ARs formation and elongation by regulating auxin signal transduction.

Phytotoxicity alleviation of imazethapyr to non-target plant wheat: active regulation between auxin and DIMBOA

Effectively controlling target organisms while reducing the adverse effects of pesticides on non-target organisms is a crucial scientific inquiry and challenge in pesticide ecotoxicology research. Here, we studied the alleviation of herbicide (R)-imazethapyr [(R)-IM] to non-target plant wheat by active regulation between auxin and secondary metabolite 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazine-3(4H)-one (DIMBOA). We found (R)-IM reduced 32.4% auxin content in wheat leaves and induced 40.7% DIMBOA accumulation compared to the control group, which effortlessly disrupted the balance between wheat growth and defense. Transcriptomic results indicated that restoration of the auxin level in plants promoted the up-regulation of growth-related genes and the accumulation of DIMBOA up-regulated the expression of defense-related genes. Auxin and DIMBOA alleviated herbicide stress primarily through effects in the two directions of wheat growth and defense, respectively. Additionally, as a common precursor of auxin and DIMBOA, indole adopted a combined growth and defense strategy in response to (R)-IM toxicity, i.e., restoring growth development and enhancing the defense system. Future regulation of auxin and DIMBOA levels in plants may be possible through appropriate methods, thus regulating the plant growth-defense balance under herbicide stress. Our insight into the interference mechanism of herbicides to the plant growth-defense system will facilitate the design of improved strategies for herbicide detoxification.

Hormonal Regulation and Stimulation Response of Jatropha curcas L. Homolog Overexpression on Tobacco Leaf Growth by Transcriptome Analysis

The Flowering locus T (FT) gene encodes the florigen protein, which primarily regulates the flowering time in plants. Recent studies have shown that FT genes also significantly affect plant growth and development. The FT gene overexpression in plants promotes flowering and suppresses leaf and stem development. This study aimed to conduct a transcriptome analysis to investigate the multiple effects of Jatropha curcas L. homolog (JcFT) overexpression on leaf growth in tobacco plants. The findings revealed that JcFT overexpression affected various biological processes during leaf development, including plant hormone levels and signal transduction, lipid oxidation metabolism, terpenoid metabolism, and the jasmonic-acid-mediated signaling pathway. These results suggested that the effects of FT overexpression in plants were complex and multifaceted, and the combination of these factors might contribute to a reduction in the leaf size. This study comprehensively analyzed the effects of JcFT on leaf development at the transcriptome level and provided new insights into the function of FT and its homologous genes.

Cytokinin-inducible response regulator SlRR6 controls plant height through gibberellin and auxin pathways in tomato

Plant height is a key agronomic trait regulated by several phytohormones such as gibberellins (GAs) and auxin. However, little is known about how cytokinin (CK) participates in this process. Here, we report that SlRR6, a type-A response regulator in the CK signaling pathway, positively regulates plant height in tomato. SlRR6 was induced by exogenous kinetin and GA3, but inhibited by indole-3-acetic acid (IAA). Knock out of SlRR6 reduced tomato plant height through shortening internode length, while overexpression of SlRR6 caused taller plants due to increased internode number. Cytological observation of longitudinal stems showed that both knock out and overexpression of SlRR6 generated larger cells, but significantly reduced cell numbers in each internode. Further studies demonstrated that overexpression of SlRR6 enhanced GA accumulation and lowered IAA content, along with expression changes in GA- and IAA-related genes. Exogenous paclobutrazol and IAA treatments restored the increased plant height phenotype in SlRR6-overexpressing lines. Yeast two-hybrid, bimolecular fluorescence complementation, and co-immunoprecipitation assays showed that SlRR6 interacts with a small auxin up RNA protein, SlSAUR58. Moreover, SlSAUR58-overexpressing plants were dwarf with decreased internode length. Overall, our findings establish SlRR6 as a vital component in the CK signaling, GA, and IAA regulatory network that controls plant height.

The ARF2-MYB6 module mediates auxin-regulated petal expansion in rose

In cut rose (Rosa hybrida), the flower-opening process is closely associated with vase life. Auxin induces the expression of transcription factor genes that function in petal growth via cell expansion. However, the molecular mechanisms underlying the auxin effect during flower opening are not well understood. Here, we identified the auxin-inducible transcription factor gene RhMYB6, whose expression level is high during the early stages of flower opening. Silencing of RhMYB6 delayed flower opening by controlling petal cell expansion through down-regulation of cell expansion-related genes. Furthermore, we demonstrated that the auxin response factor RhARF2 directly interacts with the promoter of RhMYB6 and represses its transcription. Silencing of RhARF2 resulted in larger petal size and delayed petal movement. We also showed that the expression of genes related to ethylene and petal movement showed substantial differences in RhARF2-silenced petals. Our results indicate that auxin-regulated RhARF2 is a critical player that controls flower opening by governing RhMYB6 expression and mediating the crosstalk between auxin and ethylene signaling.