Role Of Auxin Transport Research Articles

Dissecting the Herbicidal Mechanism of Microbial Natural Product Lydicamycins Using a Deep Learning-Based Nonlinear Regression Model.

The plant microbiome significantly influences plant-microbe interactions, but the mechanisms are often complex and nonlinear. Here we show the nonlinear regulatory effects of Streptomyces ginsengnesis G7 on Arabidopsis thaliana growth. We focused on lydicamycin, a molecule from this bacterium that interferes with auxin polar transport. Using a deep learning approach with a feedforward neural network, we integrated multiomics data to elucidate the mechanism of lydicamycin on plant growth and development. We also examined the impact of flavonol metabolites, particularly isorhamnetin from A. thaliana, on the PIN protein family's role in auxin transport. Our findings indicate that lydicamycin regulates auxin transport by inducing flavonol overaccumulation in A. thaliana, affecting plant development. This study identifies potential molecular targets for crop enhancement and improved agricultural productivity.

Selection of Catechin Biosynthesis-Related Genes and Functional Analysis from Chromosome-Level Genome Assembly in C. sinensis L. Variety 'Sangmok'.

Camellia is an important plant genus that includes well-known species such as C. sinensis, C. oleifera, and C. japonica. The C. sinensis cultivar 'Sangmok', one of Korea's standard types of tea landraces, is a small evergreen tree or shrub. Genome annotation has shown that Korean tea plants have special and unique benefits and superior components, such as catechin. The genome of Camellia sinensis cultivar 'Sangmok' was assembled on the chromosome level, with a length of 2678.62 Mbp and GC content of 38.16%. Further, 15 chromosome-scale scaffolds comprising 82.43% of the assembly (BUSCO completeness, 94.3%) were identified. Analysis of 68,151 protein-coding genes showed an average of 5.003 exons per gene. Among 82,481 coding sequences, the majority (99.06%) were annotated by Uniprot/Swiss-Prot. Further analysis revealed that 'Sangmok' is closely related to C. sinensis, with a divergence time of 60 million years ago. A total of 3336 exclusive gene families in 'Sangmok' were revealed by gene ontology analysis to play roles in auxin transport and cellular response mechanisms. By comparing these exclusive genes with 551 similar catechin genes, 17 'Sangmok'-specific catechin genes were identified by qRT-PCR, including those involved in phytoalexin biosynthesis and related to cytochrome P450. The 'Sangmok' genome exhibited distinctive genes compared to those of related species. This comprehensive genomic investigation enhances our understanding of the genetic architecture of 'Sangmok' and its specialized functions. The findings contribute valuable insights into the evolutionary and functional aspects of this plant species.

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

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

Comparative transcriptome and co-expression network analysis revealed the genes associated with senescence and polygalacturonase activity involved in pod shattering of rapeseed

BackgroundThe pod shattering (PS) trait negatively affects the crop yield in rapeseed especially under dry conditions. To better understand the trait and cultivate higher resistance varieties, it’s necessary to identify key genes and unravel the PS mechanism thoroughly.ResultsIn this study, we conducted a comparative transcriptome analysis between two materials significantly different in silique shatter resistance lignin deposition and polygalacturonase (PG) activity. Here, we identified 10,973 differentially expressed genes at six pod developmental stages. We found that the late pod development stages might be crucial in preparing the pods for upcoming shattering events. GO enrichment results from K-means clustering and weighed gene correlation network analysis (WGCNA) both revealed senescence-associated genes play an important role in PS. Two hub genes Bna.A05ABI5 and Bna.C03ERF/AP2-3 were selected from the MEyellow module, which possibly regulate the PS through senescence-related mechanisms. Further investigation found that senescence-associated transcription factor Bna.A05ABI5 upregulated the expression of SAG2 and ERF/AP2 to control the shattering process. In addition, the upregulation of Bna.C03ERF/AP2-3 is possibly involved in the transcription of downstream SHP1/2 and LEA proteins to trigger the shattering mechanism. We also analyzed the PS marker genes and found Bna.C07SHP1/2 and Bna.PG1/2 were significantly upregulated in susceptible accession. Furthermore, the role of auxin transport by Bna.WAG2 was also observed, which could reduce the PG activity to enhance the PS resistance through the cell wall loosening process.ConclusionBased on comparative transcriptome evaluation, this study delivers insights into the regulatory mechanism primarily underlying the variation of PS in rapeseed. Taken together, these results provide a better understanding to increase the yield of rapeseed by reducing the PS through better engineered crops.

Identification of LsPIN1 gene and its potential functions in rhizome turning of Leymus secalinus

BackgroundContinuous tilling and the lateral growth of rhizomes confer rhizomatous grasses with the unique ability to laterally expand, migrate and resist disturbances. They play key roles especially in degraded grasslands, deserts, sand dunes, and other fragile ecological system. The rhizomatous plant Leymus secalinus has both rhizome buds and tiller buds that grow horizontally and upward at the ends of rhizome differentiation and elongation, respectively. The mechanisms of rhizome formation and differentiation in L. secalinus have not yet been clarified.ResultsIn this study, we found that the content of gibberellin A3 (GA3) and indole-3-acetic acid (IAA) were significantly higher in upward rhizome tips than in horizontal rhizome tips; by contrast, the content of methyl jasmonate and brassinolide were significantly higher in horizontal rhizome tips than in upward rhizome tips. GA3 and IAA could stimulate the formation and turning of rhizomes. An auxin efflux carrier gene, LsPIN1, was identified from L. secalinus based on previous transcriptome data. The conserved domains of LsPIN1 and the relationship of LsPIN1 with PIN1 genes from other plants were analyzed. Subcellular localization analysis revealed that LsPIN1 was localized to the plasma membrane. The length of the primary roots (PRs) and the number of lateral roots (LRs) were higher in Arabidopsis thaliana plants overexpressing LsPIN1 than in wild-type (Col-0) plants. Auxin transport was altered and the gravitropic response and phototropic response were stronger in 35S:LsPIN1 transgenic plants compared with Col-0 plants. It also promoted auxin accumulation in root tips.ConclusionOur findings indicated that LsPIN1 plays key roles in auxin transport and root development. Generally, our results provide new insights into the regulatory mechanisms underlying rhizome development in L. secalinus.

Local regulation of auxin transport in root‐apex transition zone mediates aluminium‐induced Arabidopsis root‐growth inhibition

Aluminium (Al) stress is a major limiting factor for worldwide crop production in acid soils. In Arabidopsis thaliana, the TAA1-dependent local auxin biosynthesis in the root-apex transition zone (TZ), the major perception site for Al toxicity, is crucial for the Al-induced root-growth inhibition, while the mechanismunderlying Al-regulated auxin accumulation in the TZ isnot fully understood. In the present study, the role of auxin transport in Al-induced local auxin accumulation in the TZ and root-growth inhibition was investigated. Our results showed that PIN-FORMED (PIN) proteins such as PIN1, PIN3, PIN4 and PIN7 and AUX1/LAX proteins such as AUX1, LAX1 and LAX2 were all ectopically up-regulated in the root-apex TZ in response to Al stress and coordinately regulated local auxin accumulation in the TZ and root-growth inhibition. The ectopic up-regulation of PIN1 in the TZ under Al stress was regulated by both ethylene and auxin, with auxin signalling acting downstream of ethylene. Al-induced PIN1 up-regulation and auxin accumulation in the root-apex TZ was also regulated by the calossin-like protein BIG. Together, our results provide insight into how Al stress induces local auxin accumulation in the TZ and root-growth inhibition through the local regulation of auxin transport.

The PIN gene family in relic plant L. chinense: Genome-wide identification and gene expression profiling in different organizations and abiotic stress responses

The auxin efflux carrier PIN-FORMED (PIN) proteins are required for the polar transport of auxin between cells through their asymmetric distribution on the plasma membrane, thus mediating the differential distribution of auxin in plants, finally, affecting plant growth and developmental processes. In this study, 11 LcPIN genes were identified. The structural characteristics and evolutionary status of LcPIN genes were thoroughly investigated and interpreted combining physicochemical property analysis, evolutionary analysis, gene structure analysis, chromosomal localization, etc. Multi-species protein sequence analysis showed that angiosperm PIN genes have strong purification options and some functional sites were predicted about PIN protein polarity, trafficking and activity in L. chinense. Further qRT-PCR and transcriptome data analysis indicated that the long LcPINs have highly expressed from globular embryo to plantlet, and the LcPIN6a started upregulated in cotyledon embryo. The LcPIN3 and LcPIN6a are both highly expressed during the development of stamens and petals and the expression of LcPIN2 is related to root elongation, suggesting that they may play an important role in these processes. Experiment data indicates that LcPIN5 and LcPIN8 might play a key role in auxin transport in Liriodendron stems and leaves under abiotic stress. Analyzed the response of LcPIN genes to abiotic stress and as a basis for uncovering the biological role of LcPIN genes in development and adaption to adverse environments. This study provides a foundation for further genetic and functional analyses.

Seasonal nitrogen remobilization and the role of auxin transport in poplar trees.

Seasonal nitrogen (N) cycling in Populus, involves bark storage proteins (BSPs) that accumulate in bark phloem parenchyma in the autumn and decline when shoot growth resumes in the spring. Little is known about the contribution of BSPs to growth or the signals regulating N remobilization from BSPs. Knockdown of BSP accumulation via RNAi and N sink manipulations were used to understand how BSP storage influences shoot growth. Reduced accumulation of BSPs delayed bud break and reduced shoot growth following dormancy. Further, 13N tracer studies also showed that BSP accumulation is an important factor in N partitioning from senescing leaves to bark. Thus, BSP accumulation has a role in N remobilization during N partitioning both from senescing leaves to bark and from bark to expanding shoots once growth commences following dormancy. The bark transcriptome during BSP catabolism and N remobilization was enriched in genes associated with auxin transport and signaling, and manipulation of the source of auxin or auxin transport revealed a role for auxin in regulating BSP catabolism and N remobilization. Therefore, N remobilization appears to be regulated by auxin produced in expanding buds and shoots that is transported to bark where it regulates protease gene expression and BSP catabolism.

A phosphorylation-based switch controls TAA1-mediated auxin biosynthesis in plants

Auxin determines the developmental fate of plant tissues, and local auxin concentration is precisely controlled. The role of auxin transport in modulating local auxin concentration has been widely studied but the regulation of local auxin biosynthesis is less well understood. Here, we show that TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS (TAA1), a key enzyme in the auxin biosynthesis pathway in Arabidopsis thaliana is phosphorylated at Threonine 101 (T101). T101 phosphorylation status can act as an on/off switch to control TAA1-dependent auxin biosynthesis and is required for proper regulation of root meristem size and root hair development. This phosphosite is evolutionarily conserved suggesting post-translational regulation of auxin biosynthesis may be a general phenomenon. In addition, we show that auxin itself, in part via TRANS-MEMBRANE KINASE 4 (TMK4), can induce T101 phosphorylation of TAA1 suggesting a self-regulatory loop whereby local auxin signalling can suppress biosynthesis. We conclude that phosphorylation-dependent control of TAA1 enzymatic activity may contribute to regulation of auxin concentration in response to endogenous and/or external cues.

Developmental Roles of AUX1/LAX Auxin Influx Carriers in Plants.

Plant hormone auxin regulates several aspects of plant growth and development. Auxin is predominantly synthesized in the shoot apex and developing leaf primordia and from there it is transported to the target tissues e.g. roots. Auxin transport is polar in nature and is carrier-mediated. AUXIN1/LIKE-AUX1 (AUX1/LAX) family members are the major auxin influx carriers whereas PIN-FORMED (PIN) family and some members of the P-GLYCOPROTEIN/ATP-BINDING CASSETTE B4 (PGP/ABCB) family are major auxin efflux carriers. AUX1/LAX auxin influx carriers are multi-membrane spanning transmembrane proteins sharing similarity to amino acid permeases. Mutations in AUX1/LAX genes result in auxin related developmental defects and have been implicated in regulating key plant processes including root and lateral root development, root gravitropism, root hair development, vascular patterning, seed germination, apical hook formation, leaf morphogenesis, phyllotactic patterning, female gametophyte development and embryo development. Recently AUX1 has also been implicated in regulating plant responses to abiotic stresses. This review summarizes our current understanding of the developmental roles of AUX1/LAX gene family and will also briefly discuss the modelling approaches that are providing new insight into the role of auxin transport in plant development.

Studying Auxin’s Role in Ectopic Outgrowths’ Development on Leaves of the Arabidopsis thaliana taeniata Mutant

Auxin is an important inductor of organogenesis. During leaf development, local sites with high auxin concentration initiate the formation of leaf primordia and venation, control the growth of lamina and lamina margin development. The proliferative activity of the leaf cells of the Arabidopsis thalianataeniata (tae) mutant and the role of auxin in the development of the ectopic secondary margins and lobes on the leaf of the mutant were analyzed in the study. It has been established that, in addition to the ability for ectopic proliferation of leaf cells, the tae mutant demonstrates a complex of traits characteristic of plants with impaired auxin transport. It was shown that a mutation in the PID gene, which disrupts the polar auxin transport, causes the suppression of ectopic outgrowths on the leaf of the tae mutant. These data indicate the important role of auxin transport in maintaining the leaf cell pluripotency and the development of lobes on the leaf of the tae mutant.

A Positive Feedback Loop Comprising LHW-TMO5 and Local Auxin Biosynthesis Regulates Initial Vascular Development in Arabidopsis Roots.

The phytohormone auxin governs various developmental processes in plants including vascular formation. Auxin transport and biosynthesis are important factors in determining auxin distribution in tissues. Although the role of auxin transport in vein pattern formation is widely recognized, that of auxin biosynthesis in vascular development is poorly understood. Heterodimer complexes comprising two basic helix-loop-helix protein families, LONESOME HIGHWAY (LHW) and TARGET OF MONOPTEROS5 (TMO5)/TMO5-LIKE1 (T5L1), are master transcriptional regulators of the initial process of vascular development. The LHW-TMO5/T5L1 dimers regulate vascular initial cell production, vascular cell proliferation and xylem fate determination in the embryo and root apical meristem (RAM). In this study, we investigated the function of local auxin biosynthesis in initial vascular development in RAM. Results showed that LHW-T5L1 upregulated the expression of YUCCA4 (YUC4), a key auxin biosynthesis gene. The expression of YUC4 was essential for promoting xylem differentiation and vascular cell proliferation in RAM. Conversely, auxin biosynthesis was required for maintaining the expression levels of LHW, TMO5/T5L1 and their targets. Our results suggest that local auxin biosynthesis forms a positive feedback loop for fine-tuning the level of LHW-TMO5/T5L1, which is necessary for initiating vascular development.

Excessive Cellular S-nitrosothiol Impairs Endocytosis of Auxin Efflux Transporter PIN2.

S-nitrosoglutathione reductase (GSNOR1) is the key enzyme that regulates cellular levels of S-nitrosylation across kingdoms. We have previously reported that loss of GSNOR1 resulted in impaired auxin signaling and compromised auxin transport in Arabidopsis, leading to the auxin-related morphological phenotypes. However, the molecular mechanism underpinning the compromised auxin transport in gsnor1-3 mutant is still unknown. Endocytosis of plasma-membrane (PM)-localized efflux PIN proteins play critical roles in auxin transport. Therefore, we investigate whether loss of GSNOR1 function has any effects on the endocytosis of PIN-FORMED (PIN) proteins. It was found that the endocytosis of either the endogenous PIN2 or the transgenically expressed PIN2-GFP was compromised in the root cells of gsnor1-3 seedlings relative to Col-0. The internalization of PM-associated PIN2 or PIN2-GFP into Brefeldin A (BFA) bodies was significantly reduced in gsnor1-3 upon BFA treatment in a manner independent of de novo protein synthesis. In addition, the exogenously applied GSNO not only compromised the endocytosis of PIN2-GFP but also inhibited the root elongation in a concentration-dependent manner. Taken together, our results indicate that, besides the reduced PIN2 level, one or more compromised components in the endocytosis pathway could account for the reduced endocytosis of PIN2 in gsnor1-3.

Molecular cloning and functional characterization of MdPIN1 in apple

Auxin has been identified to play critical roles in regulating plant growth and development. The polar transport of auxin is regulated by auxin transporters. In the present study, an auxin efflux carrier gene MdPIN1 was cloned from Malus×domestic, Royal Gala, and introduced into wild-type Arabidopsis thaliana (Col-0). The transgenic plants exhibited the phenotype of inhibition of primary root (PR) elongation and increased lateral root (LR) number in compared with Col-0. Overexpression of MdPIN1 affected auxin transport, and enhanced phototropic responses and geotropism reaction, whereas had no significant difference in the auxin biosynthesis. These findings suggest that the MdPIN1 gene plays a vital role in auxin transport and root development.

Mitogen-activated protein kinases participate in determination of apical-basal symmetry in Pisum sativum

Mitogen-activated protein kinases (MAPKs) are implicated in various processes in plants. Apart from response to biotic and abiotic stresses they are involved in regulation of embryo development. Although MAPKs were found to be indispensable during embryo development it has never been established at which stages of embryogenesis and in which regions of a plant embryo activated MAPKs can be observed. Here, we show that apical and basal regions display activation of the same types of MAPKs and the only difference concerns the level of their phosphorylation and cellular localization. Dually-phosphorylated MAPKs were found in nuclei of the apical region of an embryo both at the early and late cotyledonary stage while no immunofluorescence signals were detected in nuclei of the basal region. However, in this case phosphorylated MAPKs were immunodetected in cytoplasm in the apical domain of cortex cells, indicating their role in auxin transport from the basal to apical region of an embryo.Furthermore, obtained data indicate that nuclear localization of activated MAPKs may result from epigenetic modifications and polar auxin transport.The presented data and previous studies lead to the conclusion that activated MAPKs and their cellular localization define apical and basal regions during formation of an apical-basal axis.

The B subfamily of plant ATP binding cassette transporters and their roles in auxin transport

The ATP binding cassette B/multidrug-resistance/P-glycoprotein (ABCB/MDR/PGP) subfamily is a member of the ABC protein family. Significant progress has been made in the functional characterization of ABCB genes, particularly in Arabidopsis thaliana. This review evaluates recent advances concerning the plant ABCB subfamilies including their evolution and structure, the involvement and regulation of ABCB-mediated auxin transport, and the roles of ABCBs in plant growth and development. Insights into specific functions of members of the ABCB subfamily and their mediation of various regulatory pathways are also presented.

English

The phytohormone auxin is crucial for plant growth and development. Transportation and distribution of auxin throughout the plant is very important to maintain the auxin homeostasis. Auxin efflux carrier genes play significant roles in auxin transport. In this study, we identified 12 auxin efflux carrier genes from the Setaria italica genome, which are similar in number with that of monocotyledonous plant Oryza sativa. Twelve (12) SiPIN genes are distributed in eight scaffolds. All the identified genes possess the transmembrane auxin efflux carrier domain. Phylogenetic analysis shows that SiPIN genes are much closer to Sorghum bicolor and O. sativa PIN genes of the grass family. Key words: Auxin efflux carrier, auxin efflux carrier domain, phosphorylation, transmembrane domain.

Auxin and its transport play a role in plant tolerance to arsenite‐induced oxidative stress in Arabidopsis thaliana

The role of auxin in plant development is well known; however, its possible function in root response to abiotic stress is poorly understood. In this study, we demonstrate a novel role of auxin transport in plant tolerance to oxidative stress caused by arsenite. Plant response to arsenite [As(III)] was evaluated by measuring root growth and markers for stress on seedlings treated with control or As(III)-containing medium. Auxin transporter mutants aux1, pin1 and pin2 were significantly more sensitive to As(III) than the wild type (WT). Auxin transport inhibitors significantly reduced plant tolerance to As(III) in the WT, while exogenous supply of indole-3-acetic acid improved As(III) tolerance of aux1 and not that of WT. Uptake assays using H(3) -IAA showed As(III) affected auxin transport in WT roots. As(III) increased the levels of H2 O2 in WT but not in aux1, suggesting a positive role for auxin transport through AUX1 on plant tolerance to As(III) stress via reactive oxygen species (ROS)-mediated signalling. Compared to the WT, the mutant aux1 was significantly more sensitive to high-temperature stress and salinity, also suggesting auxin transport influences a common element shared by plant tolerance to arsenite, salinity and high-temperature stress.

A computational model of auxin and pH dynamics in a single plant cell

Directed cell-to-cell movement of the plant growth hormone auxin is often referred to as polar auxin transport, and has gained much interest since its discovery at the beginning of the 20th century, both by biologists and theoreticians. Computational modelling of auxin transport at tissue and whole plant scales has given valuable insights into the feedback dynamics between auxin and its transport, which often leads to cell polarisation. However, one cellular feedback mechanism that has been overlooked so far in previous models is the interplay between auxin and pH during auxin transport, even though this is well known from biology. We propose a kinetic model of such a feedback mechanism, linking knowledge about auxin-induced acidification of cell wall compartments to the chemiosmotic hypothesis of auxin transport. Our results suggest that proton fluxes may play a significant role in auxin transport. Since active auxin transport relies on the proton motive force over the cellular membrane, allocation of auxin is linked to its effects on compartmental pH. Our auxin/pH feedback model predicts enhanced accumulation of auxin in cells and increases in both auxin influx and efflux when this feedback is in effect. These results were robust in all simulations and consistent with biological evidence, thus providing a framework for generating and testing hypotheses of auxin-related polarisation events at a cellular level.

Potential but limited redundant roles of MtPIN4, MtPIN5 and MtPIN10/SLM1 in the development of Medicago truncatula

Auxin polar transport is crucial in regulating plant growth and patterning. As auxin efflux carriers, the PIN FORMED (PIN) proteins are responsible for transportation of auxin out of the cell. There are eight and ten PIN members in Arabidopsis (AtPIN) and Medicago truncatula (MtPIN), respectively. Compared with MtPIN10/SMOOTH LEAF MARGIN1 (SLM1), MtPIN4 exhibits a closer relationship with AtPIN1 based phylogenetic analysis. In addition, the gene structure and distribution of transmembrane segments of MtPIN4, MtPIN5 and MtPIN10/SLM1 are similar, implying possible redundant roles among them. However, analysis using Gene Expression Atlas revealed different expression patterns among MtPIN4, MtPIN5 and MtPIN10/SLM1. Loss of function of MtPIN10/SLM1 in M. truncatula resulted in pleiotropic phenotypes in different organs, which are similar with the defects in the pin1 mutant of Arabidopsis, suggesting that the MtPIN10/SLM1 is a putative ortholog of AtPIN1. MtPIN4, MtPIN5 and MtPIN10/SLM1 may have limited redundant functions in the development of M. truncatula. The creation of double and triple mutants will help to elucidate their potential roles in auxin transport and plant development.