DUF641 family proteins have important functions in regulating plant growth and responses to environmental stress. To understand how they regulate the switch between the normal growth and salt response in woody tree, we i...DUF641 family proteins have important functions in regulating plant growth and responses to environmental stress. To understand how they regulate the switch between the normal growth and salt response in woody tree, we investigated the biological role of PtCOST3, a DUF641 family protein encoding gene, in transgenic polar. Phenotypic analyses indicated that PtCOST3 expression promoted shoot growth with increased plant height, leaf area and stem diameter, and salt sensitivity with more Na+ and less K+ accumulation in transgenic plants. The content of reactive oxygen species, malondialdehyde and proline was significantly increased, whereas the activity of antioxidant enzymes was significantly decreased, in PtCOST3 transgenic plants. Further sub-cellular location and protein interaction studies demonstrated that PtCOST3 co-localized and directly interacted with the autophagy protein ATG8e in the autophagosomes, and PtCOST3 expression reduced the autophagy activity, as indicated by the decreased autophagosome number, in transgenic plants under both normal and stress conditions. Our results demonstrate that PtCOST3 positively regulates the normal growth but negatively modulates the salt tolerance by precisely manipulating the autophagy switch in plants.
Abscisic acid (ABA) is a key phytohormone that regulates stomatal movement, seed germination, root development, and stress responses. Here, we report that Arabidopsis (Arabidopsis thaliana) ATP-binding cassette (ABC) tra...Abscisic acid (ABA) is a key phytohormone that regulates stomatal movement, seed germination, root development, and stress responses. Here, we report that Arabidopsis (Arabidopsis thaliana) ATP-binding cassette (ABC) transporter G family member 21 (AtABCG21) functions as an ABA transporter that plays a role in seed germination under salt stress. AtABCG21 exhibits efflux transporter activity toward ABA in tobacco (Nicotiana benthamiana) and yeast (Saccharomyces cerevisiae) cells. β-glucuronidase (GUS) staining showed that AtABCG21, predominantly expressed in embryos and vascular tissues, is induced by ABA and salt stress, respectively. Subcellular localization analysis of GFP-AtABCG21 in N. benthamiana leaves indicated that AtABCG21 localizes to the plasma membrane. The inflorescence intensity of the ABSCISIC ACID RESPONSIVE ELEMENT (ABRE)-based synthetic promoter-driven GFP reporter ABRE::GFP was significantly reduced in the embryos of the atabcg21 mutant under salt stress, suggesting that disruption of AtABCG21 compromised ABA signaling in the embryo. Consistently, quantification of ABA and ABA-GE revealed that the levels of ABA, but not ABA-GE, in the seeds of the atabcg21 mutant were significantly reduced compared to those in wild-type plants under salt stress. Consequently, the seed germination rate of the atabcg21 mutants was increased compared to that of wild-type plants under salt stress. These results demonstrate that AtABCG21 acts as an ABA efflux transporter, facilitating ABA translocation and influencing seed germination under salt stress. Our findings provide new insights into the mechanisms of ABA-mediated stress adaptation in plants.
Citric acid is the major organic acid affecting citrus fruit taste, which varies widely in the citrus family. An acidless kumquat, a small-fruited citrus species (Citrus crassifolia), has been developed and has become po...Citric acid is the major organic acid affecting citrus fruit taste, which varies widely in the citrus family. An acidless kumquat, a small-fruited citrus species (Citrus crassifolia), has been developed and has become popular on the market. To investigate the molecular basis of the acidless phenotype in Huapi (HP) kumquat, it was crossed with early-flowering, high-acid Hong Kong (HK) kumquat to generate an F1 population, providing a system to dissect the genetic and molecular basis of citric acid accumulation. Organic acid content exhibited a wide and continuous distribution across three consecutive years, which is consistent with quantitative inheritance. Bulked segregant analysis sequencing mapped a major locus, and integration with transcriptomic data identified the GRAS transcription factor SCARECROW-like protein 9 (ChSCL9) as a candidate major-effect gene, showing high expression in HP fruit and low expression in HK fruit. Subcellular localization confirmed that ChSCL9 is a transcription factor. Functional analyses-including CRISPR-Cas9 gene editing, overexpression in kumquat, and RNA interference (RNAi) in citrus juice sacs-demonstrated that ChSCL9 negatively regulates citric acid accumulation. Biochemical experiments showed that ChSCL9 directly represses the expression of the R2R3-MYB gene ChPH4 and the vacuolar P-ATPase gene ChPH5, both of which are key genes for vacuolar acidification, thereby inhibiting citric acid accumulation. These results identify ChSCL9 as a key regulator of citric acid in kumquat, reveal an upstream regulator of PH4, and provide targets for citrus flavor improvement and rational design for citrus breeding.
MAPK activation is a key event downstream of receptor-mediated signaling in plant immunity and development. While the activation of MAPK cascades is well-studied, their negative regulatory mechanisms remain less understo...MAPK activation is a key event downstream of receptor-mediated signaling in plant immunity and development. While the activation of MAPK cascades is well-studied, their negative regulatory mechanisms remain less understood. Expression profiling of conditional gain-of-function MPK3/MPK6 plants identified the induction of Clade B phosphatase genes from the PP2C family, known as AP2Cs. Overexpression of any of the four AP2C members suppresses MAPK activation in seedlings treated with flg22. Additionally, these plants exhibited excessive stomatal formation and clustering, phenocopying mpk3 mpk6 mutants. In contrast, single AP2C loss-of-function mutants show no discernible phenotype, suggesting functional redundancy. Mutation of all four AP2C members leads to enhanced MPK3/MPK6 activation and accelerated cell death upon pathogen infection. Loss of MPK6 in the ap2c1/2/3/4 quadruple mutant background confirmed that MPK6 is a key target of AP2Cs in regulating HR cell death. Further investigation revealed that the MPK3/MPK6 and CPK5/CPK6, two critical immune signaling pathways, along with their downstream substrate, WRKY33, are involved in the activation of AP2C expression in response to PAMP treatment and pathogen infection. We conclude that AP2C1/2/3/4 function as MAPK phosphatases, collectively forming a negative feedback regulatory loop that fine-tunes the signaling strength and duration of MPK3/MPK6 cascade to balance plant immunity and development.
Specialized metabolites are often distributed sporadically across distantly related plant lineages, a pattern commonly attributed to convergent evolution, although the genomic processes enabling such innovation remain po...Specialized metabolites are often distributed sporadically across distantly related plant lineages, a pattern commonly attributed to convergent evolution, although the genomic processes enabling such innovation remain poorly understood. Here, we demonstrate that parasitic dodders (Cuscuta spp.) accumulate the lignan sesamin, a compound previously considered characteristic of sesame (Sesamum indicum) and related Lamiales species. We identified Cuscuta homologs of S. indicum CYP81Q1, which encodes piperitol/sesamin synthase (PSS), and demonstrated that these proteins retain catalytic PSS activity in vitro. Phylogenetic analyses indicate that CYP81Q was horizontally transferred from a Lamiales host to an ancestral Cuscuta lineage. Parasitism by C. campestris induces host CYP81Q expression and enhances interspecific transfer of genetic material across the haustorial interface, providing a mechanistic basis for horizontal gene transfer (HGT). Notably, comparative genomic analyses reveal that following horizontal acquisition, the transferred gene underwent extensive structural remodeling, characterized by sequential intron gains, while its enzymatic function was preserved. Many of the newly acquired introns exhibit hallmarks of insertion and excision of transposable elements, suggesting that mobile genetic elements contributed to post-transfer gene restructuring. The intron-rich architecture of Cuscuta CYP81Q was stably maintained throughout species diversification. Together, these findings suggest that parasitism-mediated HGT can be followed by intronization and transposon colonization, resulting in the generation of structurally complex yet functional genes. This process represents an underappreciated mechanism through which parasitic plants remodel horizontally acquired genes to facilitate metabolic innovation.
Zeiner A, Krasensky-Wrzaczek J, Jindal S
… +12 more, Sun Y, Ušák D, Hajný J, Sharma M, Morina F, Andresen E, Pääkkönen M, Küpper H, Merilahti J, Pleskot R, Melnyk CW, Wrzaczek M
CYSTEINE-RICH RECEPTOR-LIKE PROTEIN KINASEs (CRKs) play an important role in plant development and stress responses. One of the best described members of the Arabidopsis CRK family is CRK2, which was proposed as a crucia...CYSTEINE-RICH RECEPTOR-LIKE PROTEIN KINASEs (CRKs) play an important role in plant development and stress responses. One of the best described members of the Arabidopsis CRK family is CRK2, which was proposed as a crucial regulator of intercellular transport facilitated by plasmodesmata (PD). As intercellular channels allowing symplastic communication, PD-mediated transport is predominantly regulated by callose synthase (CALS)-mediated callose deposition. This process can impact not just the distribution of molecules between adjacent cells, but also the symplastic loading of vascular tissue, thereby influencing plant stress responses and developmental processes. Here we described the overlapping expression pattern of genes encoding phylogenetically closely related CALS1 and CALS3. Both CALSs were phosphorylated in vitro by CRK2, and the genetic interaction between genes encoding CRK2 and CALS1 or CALS3 revealed their impact on callose deposition, rosette growth, primary root length, and development, represented as a decreased number of true leaves. Importantly, we observed significant accumulation of starch in crk2 mutant plants, especially in developmentally older leaves, which was reverted by the independent introduction of cals1.5 and cals3.1 into the crk2 mutant background. The observed starch accumulation was accompanied by photosynthesis inhibition. We propose that the growth and developmental alterations of crk2 are caused by decreased phloem loading, which resulted in starch accumulation in source organs, and subsequent sink tissue starvation. Our results propose CRK2 as negative regulator of CALS1 and CALS3 regulating source to sink transport, which impacts plant growth and development.
Previous studies have shown that hydrogen peroxide (H2O2) treatment promotes early ripening in 'Kyoho' grapes (Vitis vinifera × Vitis labrusca); however, the mechanism by which H2O2 oxidation modification regulates grape...Previous studies have shown that hydrogen peroxide (H2O2) treatment promotes early ripening in 'Kyoho' grapes (Vitis vinifera × Vitis labrusca); however, the mechanism by which H2O2 oxidation modification regulates grape ripening remains unclear. Here, RNA-Seq data revealed substantial downregulation of small Heat Shock Protein 20-43 (VvHSP20-43) expression levels in the treated group. Co-expression network analysis identified MYB Altered Phloem Development (VvMYB APL) as a key regulator of VvHSP20-43 expression. Dual luciferase, yeast one-hybrid, and electrophoretic mobility shift assays confirmed that VvMYB APL binds to the VvHSP20-43 promoter, thereby activating its transcriptional expression. Stable transformation in Arabidopsis and transient transformation in grape berries demonstrated that VvMYB APL and VvHSP20-43 negatively regulate fruit ripening. Further analysis revealed that exogenous H2O2 treatment rapidly oxidizes the VvMYB APL protein, inducing methionine (Met) site mutations that inhibit its transcriptional activation of VvHSP20-43. In addition, reduced expression of VvMYB APL and VvHSP20-43 promoted the expression of ripening-related genes, thereby accelerating grape berry ripening. This study elucidates the molecular mechanism by which H2O2 oxidizes the VvMYB APL transcription factor, thereby downregulating VvHSP20-43 expression and influencing fruit ripening.
The densification of cereal crops increases population but simultaneously reduces the grain number per individual plant, constraining harvest index and overall yield. Since asynchronous pollination within spike/ear is co...The densification of cereal crops increases population but simultaneously reduces the grain number per individual plant, constraining harvest index and overall yield. Since asynchronous pollination within spike/ear is conserved among cereals, its role in determining yield formation under densification remains unclear. Here, we varied pollination time gaps (PTG, defined as the duration required for all silks in an ear to emerge and be pollinated) to examine how PTG affects grain development and overall yield as planting density increases. Results showed that densification exacerbated PTG and increased grain abortion. Eliminating PTG through synchronous pollination (SP) recovered more than 20% of density-induced grain loss per ear and increased harvest index by 3.7∼3.9% and total yield by 4.9∼11.7%, along with higher optimal density. Using 13C-labeling to quantify daily carbon assimilates, SP increased carbon allocation to the ear and grains, while significantly decreasing carbon stored in vegetative tissues. Surprisingly, photosynthesis rates were also enhanced during the subsequent filling stage. These findings suggest a synergistic enhancement of sink and source capacities under densified populations with SP. Additionally, removing early pollinated grains at the grain set stage increased carbon availability to later-pollinated grains and prevented their abortion, confirming PTG's role in carbon allocation within the ear for determining grain number. Validated across different varieties and years, we propose PTG as a new trait for breeding and management to enhance harvest index and yield potential in densified populations. This sink modulation approach complements existing strategies focused on improving source capacity and may be applicable across various cereals with asynchronous flowering.
Flavonols are important secondary metabolites that protect plants against UV-B stress. Although plant miRNAs can fine-tune abiotic stress responses, their role in regulating the biosynthesis of UV-B-induced flavonols rem...Flavonols are important secondary metabolites that protect plants against UV-B stress. Although plant miRNAs can fine-tune abiotic stress responses, their role in regulating the biosynthesis of UV-B-induced flavonols remains unclear. Treatment with UV-B radiation markedly increased the levels of quercetin glycosides in Chinese bayberry fruits (Morella rubra cv. Biqi). The expression of the flavonol-related transcription factors, MrMYB12, MrHY5, and quercetin biosynthesis genes was induced by UV-B. Using degradome sequencing and qRT-PCR, we identified an mru-miR396-MrGRF4 module in which mru-miR396 was downregulated and MrGRF4 was upregulated by UV-B. Assays in tobacco showed that mru-miR396 suppresses the expression of MrGRF4. Transient overexpression of mru-MIR396b or silencing MrGRF4 increased flavonol accumulation in 'Biqi' leaves. Conversely, silencing mru-miR396 or overexpressing MrGRF4 decreased flavonol content. When untargeted by miRNA, MrGRF4 represses the promoter activities of MrF3H, MrF3'H, MrFLS1, and MrFLS2, reducing the positive effect of MrMYB12 on quercetin biosynthesis in tobacco. In addition, MrGRF4 could bind to the promoter of MrMYB12 and directly inhibit its expression. Transient co-overexpression of MrGRF4 and MrMYB12 in 'Biqi' and tobacco leaves attenuated quercetin biosynthesis compared to overexpression of MrMYB12 alone. Furthermore, MrHY5 was found to directly suppress the expression of mru-miR396. Transient expression of MrHY5 increased the content of flavonol by upregulating MrMYB12, MrGRF4, flavonol biosynthesis genes, and downregulating mru-miR396, while silencing had opposite effects. Overall, MrMYB12 acts as a key activator of quercetin biosynthesis, while the MrHY5-mru-miR396-MrGRF4 cascade weakens the regulatory effect of MrMYB12, preventing excessive quercetin accumulation under UV-B. These results provide evidence for a mechanism that balances the biosynthesis of secondary metabolites in plants in response to UV-B.
The CBF-dependent signaling pathway plays a central role in cold acclimation in potato; however, the transcriptional regulators controlling expression of StCBFs remain poorly understood. Here, we identified StC3H14, a CC...The CBF-dependent signaling pathway plays a central role in cold acclimation in potato; however, the transcriptional regulators controlling expression of StCBFs remain poorly understood. Here, we identified StC3H14, a CCCH-type zinc finger transcription factor, which directly activates StCBF1 and StCBF3 by directly binding to their promoters. Overexpression of StC3H14 in potato significantly enhanced cold tolerance, as shown by higher survival rates, reduced electrolyte leakage, and increased soluble sugar accumulation compared with wild-type and RNAi lines. Consistently, the expression of CBF-regulated COR genes was upregulated in overexpression lines. Moreover, under chilling conditions (15 ℃ day/10 ℃ night), StC3H14 overexpression produced significantly higher tuber yield per plant than wild-type and RNAi plants. Our findings establish StC3H14 as a key regulator of the CBF-dependent signaling pathway and highlight its potential for improving cold tolerance and yield in potato.
Jasmonic acid (JA) and polyamines (PAs) are key regulators of fruit ripening, yet their functional association remains largely unresolved. Here, we demonstrate that exogenous methyl jasmonate (MeJA) application markedly...Jasmonic acid (JA) and polyamines (PAs) are key regulators of fruit ripening, yet their functional association remains largely unresolved. Here, we demonstrate that exogenous methyl jasmonate (MeJA) application markedly reduces PA accumulation and accelerates peach (Prunus persica L.) fruit ripening. Transcriptomic analysis revealed significant upregulation of peach polyamine oxidase1 (PpePAO1), a key gene in PA catabolism, following MeJA treatment. Using the PpePAO1 promoter as bait, we identified the JA signaling transcription factor myeloblastosis family 2 (PpeMYC2). MeJA treatment suppressed PpeMYC2 expression, and subsequent yeast one-hybrid (Y1H), electrophoretic mobility shift assay (EMSA), and dual-luciferase assay confirmed that PpeMYC2 directly binds to the PpePAO1 promoter to repress its transcriptional activity. Silencing PpeMYC2 led to decreased PA levels and accelerated fruit ripening, whereas PpeMYC2 overexpression produced the opposite effect. Additionally, PpeMYC2 activated the arginine decarboxylase (PpeADC1) promoter, thereby enhancing PA biosynthesis. Beyond PA regulation, silencing PpeMYC2 significantly increased anthocyanin accumulation by relieving its repression of dihydro flavonol 4-reductase (PpeDFR), a key gene in anthocyanin biosynthesis. Collectively, these findings reveal that JA promotes peach fruit ripening by lowering PA accumulation and stimulating anthocyanin synthesis through PpeMYC2-mediated transcriptional control. This study provides mechanistic evidence that JA regulates fruit ripening through direct control of PA metabolism and identifies PpeMYC2 as a central node integrating JA, PA, and anthocyanin pathways in peach fruit.
Xylem pit membranes are discrete regions of primary cell wall that are permeable to water but prevent the spread of air embolism. Here we investigate how pectin, a cell wall hydrogel with a kPa-scale modulus, affects the...Xylem pit membranes are discrete regions of primary cell wall that are permeable to water but prevent the spread of air embolism. Here we investigate how pectin, a cell wall hydrogel with a kPa-scale modulus, affects the functioning of intervessel pit membranes in Acer rubrum (red maple). We show that enzymatically digesting pectin significantly lowers the resistance against embolism spread, confirming earlier reports in other species and providing evidence that pectin is present in at least some portions of A. rubrum's intervessel pit membranes. Removing calcium with a chelating agent had a smaller effect that became non-significant after accounting for radial flows. Vulnerability curves of control and calcium removal stems measured with and without the addition of a surfactant (0.1% w/v Triton-X) exhibited large differences in P50 as expected for the change in surface tension and implying an invariant effective Laplace radius. In contrast, pectin removal stems did not exhibit a significant change in P50 when vulnerability curves were measured with and without surfactant. Instead, the difference in surface tension implied large changes in the effective Laplace radius with increasing xylem tension, suggesting that pectin removal increases the local compliance of pit membranes. We hypothesize that pectin stabilizes the spacing of cellulose microfibrils, thereby contributing to the transport of water under tension.
Optimizing plant architecture without compromising disease resistance is a fundamental challenge in crop breeding, particularly for space-efficient systems such as vertical farming (VF). Here, we identify the YABBY-famil...Optimizing plant architecture without compromising disease resistance is a fundamental challenge in crop breeding, particularly for space-efficient systems such as vertical farming (VF). Here, we identify the YABBY-family transcription factor SlYABBY5b as a pivotal regulator that synchronizes these traits in tomato. Through a genome-wide association study (GWAS), we establish SlYABBY5b as a major locus governing natural variation in plant height. Functional analyses reveal that SlYABBY5b directly orchestrates gibberellin (GA) metabolism by activating the inactivation gene SlGA2ox2 and repressing the biosynthetic gene SlGA3ox1, thereby reducing bioactive GA pools and causing GA-reversible dwarfism. In parallel, SlYABBY5b enhances resistance to the major greenhouse pathogen Botrytis cinerea by directly targeting the promoters of the immune genes SlNLR and SlPR1a. Evolutionary analyses reveal functional divergence: while SlYABBY5b acts redundantly with its paralog SlYABBY5a in growth regulation, it has acquired a specialized, non-redundant role in enhancing basal immunity. Furthermore, natural promoter haplotypes of SlYABBY5b associate with stature and show signs of selection during domestication, positioning SlYABBY5b as a key target for breeding compact crops. Our findings illustrate how a single transcription factor can coordinate compact architecture with enhanced immunity, offering a promising target for developing resilient, high-density crops for controlled-environment agriculture.
Inorganic phosphate (Pi) deficiency severely limits tree growth and productivity. The challenge of phosphorus acquisition extends beyond the scarcity of Pi, as the utilization of organic phosphorus represents another cri...Inorganic phosphate (Pi) deficiency severely limits tree growth and productivity. The challenge of phosphorus acquisition extends beyond the scarcity of Pi, as the utilization of organic phosphorus represents another critical yet poorly understood adaptation in woody plants. Here, we identify a synergistic regulatory module involving the R2R3-MYB transcription factor PuMYB40 and the WRKY factor PuWRKY75 that enhances organic phosphorus scavenging and Pi uptake in Populus ussuriensis under Pi-deficient conditions. Overexpression of PuMYB40 or PuWRKY75 enhanced Pi acquisition and plant growth when phytate was supplied as the sole phosphorus source or under low-Pi conditions, whereas suppression had the opposite effects. RNA sequencing revealed that both factors activate numerous Pi starvation-responsive genes, with over 60% of PuMYB40-regulated genes overlapping with those controlled by PuWRKY75. Molecular analyses demonstrated that PuMYB40 and PuWRKY75 directly activate the expression of PuPAP17 (encoding a rhizosphere-secreted acid phosphatase), PuPHT1;4 (a high-affinity Pi transporter), PuPHT1;9 (a root-to-shoot Pi translocator) and PuGDPD1 (which facilitates phospholipid remodeling) by binding to distinct cis-elements in their promoters. Overexpression of PuPAP17 or PuPHT1;4 increased organic phosphorus hydrolysis when phytate was supplied as the sole phosphorus source and phosphate uptake under low-Pi conditions, respectively. Transient dual-luciferase and microscale thermophoresis assays revealed that PuWRKY75 and PuMYB40 interact, and this interaction amplifies the transcriptional activation of PuPAP17 and PuPHT1;4 by PuMYB40 but not by PuWRKY75. Our findings establish a coordinated "decompose-import" regulatory axis in poplar, providing mechanistic insights and genetic tools for improving phosphorus-use efficiency in forest trees.
Understanding root system architecture (RSA) is critical for improving crop productivity and resilience, yet phenotyping root traits such as root growth angle and rooting depth remains technically challenging, especially...Understanding root system architecture (RSA) is critical for improving crop productivity and resilience, yet phenotyping root traits such as root growth angle and rooting depth remains technically challenging, especially at high throughput. Here, we present ClearDepthIAS, a high-throughput imaging and analysis platform that enables non-destructive, automated quantification of root architecture traits in taproot system crops. By capturing and stitching 360° images of roots growing along the transparent walls of pots and applying deep learning-based segmentation (ClearDepth-WRT), we measured wall root shallowness (WRS)-a proxy for root growth angle-with high precision. We demonstrated for the tap root systems of soybean and canola that the system accurately detects root tips, quantifies their vertical distribution, and extracts biologically meaningful traits such as root area, distribution indices, and growth angles. Validation experiments in canola and soybean demonstrated that WRS can correlate with root crown architecture in mature plants, both in greenhouse and field settings. Furthermore, WRS and root distribution indices derived from ClearDepthIAS are predictors of early root architecture and can be correlated with root biomass distribution across soil depths under field conditions; however, environmental interactions may influence these relationships and weaken or even negate such correlations, as observed when comparing field to field variation in root system architecture. Our system enables efficient phenotyping of genetically diverse populations, with medium to high trait heritability, supporting its utility for genome-wide association studies and breeding. ClearDepthIAS accelerates the development of root ideotypes for improved resource acquisition and carbon sequestration, offering a scalable tool for supporting climate-resilient agriculture.
Ever since Went first characterized auxins in 1928, the evolutionary history of this phytohormone and its underlying pathway has remained a foundational question for the plant science community. In this study, we compreh...Ever since Went first characterized auxins in 1928, the evolutionary history of this phytohormone and its underlying pathway has remained a foundational question for the plant science community. In this study, we comprehensively traced the origin and diversification of auxin biosynthesis, metabolism, transport, and signaling pathways across plant lineages. Here, we proposed a model of how protein interactions involved in auxin signaling gradually became established over evolution, evaluated the evolutionary similarities and differences among these pathways, and found that these evolutionary patterns align closely with the mutational and selective landscapes observed in natural populations of Arabidopsis thaliana. Notably, auxin-related pathways exhibited generally low conservation in algae. However, in Klebsormidium nitens, genes responsive to auxin induction were generally enriched in various auxin-related pathways. To further identify and fill the gaps in the auxin pathway in Algae, we conducted a protein structural prediction and identified candidate proteins with highly conserved structures of TMK1, ABP1 and TIR1 auxin receptors between Algae and a higher evolutionary status plant such as A. thaliana.