Phytohormones Salicylic Acid Research Articles

Combination of transcriptomic, proteomic and degradomic profiling reveals common and distinct patterns of pathogen-induced cell death in maize.

Regulated cell death (RCD) is crucial for plant development, as well as in decision-making in plant-microbe interactions. Previous studies revealed components of the molecular network controlling RCD, including different proteases. However, the identity, the proteolytic network as well as molecular components involved in the initiation and execution of distinct plant RCD processes, still remain largely elusive. In this study, we analyzed the transcriptome, proteome and N-terminome of Zea mays leaves treated with the Xanthomonas effector avrRxo1, the mycotoxin Fumonisin B1 (FB1), or the phytohormone salicylic acid (SA) to dissect plant cellular processes related to cell death and plant immunity. We found highly distinct and time-dependent biological processes being activated on transcriptional and proteome levels in response to avrRxo1, FB1 and SA. A correlation analysis of the transcriptome and proteome identified general, as well as trigger-specific markers for cell death in Z. mays. We found that proteases, particularly papain-like cysteine proteases, are specifically regulated during RCD. Collectivley, this study characterizes distinct RCD responses in Z. mays and provides a framework for the mechanistic exploration of components involved in the initiation and execution of cell death.

Molecular Mechanism of miR160d in Regulating Kiwifruit Resistance to Botrytis cinerea.

Gray mold caused by Botrytis cinerea leads to huge economic losses to the kiwifruit (Actinidia chinensis) industry. Elucidating the molecular mechanism responding to B. cinerea is the theoretical basis for the resistance to molecular breeding of kiwifruit. Previous studies have shown that miR160 regulates plant disease resistance through the indole-3-acetic acid (IAA) signaling pathway. In this study, kiwifruit "Hongyang" was used as the material, and Ac-miR160d and its target genes were identified and cloned. Overexpression and virus-induced gene silencing (VIGS) technology combined with RNA-seq were adopted to analyze the regulatory role of Ac-miR160d in kiwifruit resistance to B. cinerea. Silencing Ac-miR160d (AcMIR160d-KN) increased kiwifruit sensitivity to B. cinerea, whereas overexpression of Ac-miR160d (AcMIR160d-OE) increased kiwifruit resistance to B. cinerea, suggesting that Ac-miR160d positively regulates kiwifruit resistance to B. cinerea. In addition, overexpression of Ac-miR160d in kiwifruit increased antioxidant enzyme activities, such as catalase (CAT) and superoxide dismutase (SOD), and endogenous phytohormone IAA and salicylic acid (SA) content, in response to B. cinerea-induced stress. RNA-seq identified 480 and 858 unique differentially expressed genes in the AcMIR160d-KN vs CK and AcMIR160d-OE vs CK groups, respectively, with fold change ≥2 and false discovery rate <0.01. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that families associated with "biosynthesis of secondary metabolites" are possibly regulated by Ac-miR160d. "Phenylpropanoid biosynthesis", "flavonoid biosynthesis", and "terpenoid backbone biosynthesis" were further activated in the two comparison groups upon B. cinerea infection. Our results may reveal the molecular mechanism by which miR160d regulates kiwifruit resistance to B. cinerea and may provide gene resources for molecular breeding in kiwifruit resistance.

Nucleoredoxin gene SINRX1 negatively regulates tomato immunity by activating SA signaling pathway

The tomato (Solanum lycopersicum) is widely consumed globally and renowned for its health benefits, including the reduction of cardiovascular disease and prostate cancer risk. However, tomato production faces significant challenges, particularly due to various biotic stresses such as fungi, bacteria, and viruses. To address this challenges, we employed the CRISPR/Cas9 system to modify the tomato NUCLEOREDOXIN (SlNRX) genes (SlNRX1 and SlNRX2) belonging to the nucleocytoplasmic THIOREDOXIN subfamily. CRISPR/Cas9-mediated mutations in SlNRX1 (slnrx1) plants exhibited resistance against bacterial leaf pathogen Pseudomonas syringae pv. maculicola (Psm) ES4326, as well as the fungal pathogen Alternaria brassicicola. However, the slnrx2 plants did not display resistance. Notably, the slnrx1 demonstrated elevated levels of endogenous salicylic acid (SA) and reduced levels of jasmonic acid after Psm infection, in comparison to both wild-type (WT) and slnrx2 plants. Furthermore, transcriptional analysis revealed that genes involved in SA biosynthesis, such as ISOCHORISMATE SYNTHASE 1 (SlICS1) and ENHANCED DISEASE SUSCEPTIBILITY 5 (SlEDS5), were upregulated in slnrx1 compared to WT plants. In addition, a key regulator of systemic acquired resistance, PATHOGENESIS-RELATED 1 (PR1), exhibited increased expression in slnrx1 compared to WT. These findings suggest that SlNRX1 acts as a negative regulator of plant immunity, facilitating infection by the Psm pathogen through interference with the phytohormone SA signaling pathway. Thus, targeted mutagenesis of SlNRX1 is a promising genetic means to enhance biotic stress resistance in crop breeding.

A Streptomyces Consortium Contributes Distinct Microbial Interactions During Arabidopsis thaliana Microbiome Assembly

Although plant microbiome assembly involves a series of both plant–microbe and microbe–microbe interactions, the latter is less often directly tested. Here, we investigate a role for Streptomyces strains to influence assembly of other bacteria into root microbiomes through the use of two synthetic communities (SynComs): a 21-member community including four Streptomyces strains and a 17-member community lacking those Streptomyces strains. Following inoculation with these SynComs on wild-type Arabidopsis thaliana Col-0, differential abundance modeling on root endosphere 16S ribosomal RNA gene amplicon sequencing data revealed altered abundance of four diverse SynCom members: Arthrobacter sp. 131, Agrobacterium sp. 33, Burkholderia sp. CL11, and Ralstonia sp. CL21. Modeling results were tested by seedling coinoculation experiments with the four Streptomyces strains and differentially abundant members, which confirmed the predicted decreased abundance for Arthrobacter sp. 131, Agrobacterium sp. 33, and Ralstonia sp. CL21 when Streptomyces strains were present. We further characterized how the phytohormone salicylic acid (SA) mediates Streptomyces strains’ influence over Agrobacterium sp. 33 and Burkholderia sp. CL11 seedling colonization. Although decreased colonization of Ralstonia sp. CL21 and Arthrobacter sp. 131 when Streptomyces spp. are present were not influenced by SA, direct antibiosis of Arthrobacter sp. 131 by Streptomyces was observed. These results highlight a role for Streptomyces-mediated microbial interactions during plant root microbiome assembly as well as distinct mechanisms that mediate them. Understanding the role of microbial interactions during microbiome assembly will inform the production of beneficial microbial treatments for use in agricultural fields.

The Peroxisomal β-Oxidative Pathway and Benzyl Alcohol O-Benzoyltransferase HSR201 Cooperatively Contribute to the Biosynthesis of Salicylic Acid.

The phytohormone salicylic acid (SA) regulates plant defense responses against pathogens. Previous studies have suggested that SA is mainly produced from trans-cinnamic acid (CA) in tobacco, but the underlying mechanisms remain largely unknown. SA synthesis is activated by wounding in tobacco plants in which the expression of WIPK and SIPK, two stress-related mitogen-activated protein kinases, is suppressed. Using this phenomenon, we previously revealed that HSR201 encoding benzyl alcohol O-benzoyltransferase is required for pathogen signal-induced SA synthesis. In this study, we further analyzed the transcriptomes of wounded WIPK-/SIPK-suppressed plants and found that the expression of NtCNL, NtCHD and NtKAT1, homologous to cinnamate-coenzyme A (CoA) ligase (CNL), cinnamoyl-CoA hydratase/dehydrogenase (CHD) and 3-ketoacyl-CoA thiolase (KAT), respectively, is associated with SA biosynthesis. CNL, CHD and KAT constitute a β-oxidative pathway in the peroxisomes and produce benzoyl-CoA, a precursor of benzenoid compounds in petunia flowers. Subcellular localization analysis showed that NtCNL, NtCHD and NtKAT1 localize in the peroxisomes. Recombinant NtCNL catalyzed the formation of CoA esters of CA, whereas recombinant NtCHD and NtKAT1 proteins converted cinnamoyl-CoA to benzoyl-CoA, a substrate of HSR201. Virus-induced gene silencing of any one of NtCNL, NtCHD and NtKAT1 homologs compromised SA accumulation induced by a pathogen-derived elicitor in Nicotiana benthamiana leaves. Transient overexpression of NtCNL in N. benthamiana leaves resulted in SA accumulation, which was enhanced by co-expression of HSR201, although overexpression of HSR201 alone did not cause SA accumulation. These results suggested that the peroxisomal β-oxidative pathway and HSR201 cooperatively contribute to SA biosynthesis in tobacco and N. benthamiana.

Cross-Talk between Iron Deficiency Response and Defense Establishment in Plants

Plants are at risk of attack by various pathogenic organisms. During pathogenesis, microorganisms produce molecules with conserved structures that are recognized by plants that then initiate a defense response. Plants also experience iron deficiency. To address problems caused by iron deficiency, plants use two strategies focused on iron absorption from the rhizosphere. Strategy I is based on rhizosphere acidification and iron reduction, whereas Strategy II is based on iron chelation. Pathogenic defense and iron uptake are not isolated phenomena: the antimicrobial phenols are produced by the plant during defense, chelate and solubilize iron; therefore, the production and secretion of these molecules also increase in response to iron deficiency. In contrast, phytohormone jasmonic acid and salicylic acid that induce pathogen-resistant genes also modulate the expression of genes related to iron uptake. Iron deficiency also induces the expression of defense-related genes. Therefore, in the present review, we address the cross-talk that exists between the defense mechanisms of both Systemic Resistance and Systemic Acquired Resistance pathways and the response to iron deficiency in plants, with particular emphasis on the regulation genetic expression.

Phytohormones unlocking their potential role in tolerance of vegetable crops under drought and salinity stresses.

Globally, abiotic stresses are drastically reducing the productivity of vegetable crops. Among abiotic stresses, drought and salinity are more challenging constraints for the sustainable production of vegetables. A great variety of vegetables are facing dry and hot summer spells, poor water availability, and higher salinity mainly due to irrigation with brackish water. Vegetables are considered higher water-dependent crops, requiring water for proper growth and yield. Drought and salinity impair plant metabolism. The disruption in plant metabolism leads to a reduction in growth, developmental processes, and ultimately crop yield. Appropriate management measures are needed to cope with the adverse effects of drought and salinity. Different agronomic and molecular approaches contributed to improving tolerance. Therefore, the present review significantly explores the impact of phytohormones on vegetable crops under drought and salinity stresses. Phytohormones (salicylic acid, melatonin, jasmonates, Brassinosteroids, ascorbic acid, and numerous others) can be sprayed for improvement of plant growth, yield, and photosynthetic pigments by modulation of physiological and biochemical processes. In this manner, these phytohormones should be explored for sustainable production of vegetable crops growing under abiotic stress conditions.

Salicylic acid biosynthesis is not from phenylalanine in Arabidopsis.

The phytohormone salicylic acid (SA) regulates biotic and abiotic stress responses in plants. Two distinct biosynthetic pathways for SA have been well documented in plants: the isochorismate (IC) pathway in the chloroplast and the phenylalanine ammonia-lyase (PAL) pathway in the cytosol. However, there has been no solid evidence that the PAL pathway contributes to SA biosynthesis. Here, we report that feeding Arabidopsis thaliana with Ring-13 C-labeled phenylalanine (13 C6 -Phe) resulted in incorporation of the 13 C label not into SA, but into its isomer 4-hydroxybenzoic acid (4-HBA) instead. We obtained similar results when feeding 13 C6 -Phe to the SA-deficient ics1 ics2 mutant and the SA-hyperaccumulating mutant s3h s5h. Notably, we detected 13 C6 -SA when 13 C6 -benzoic acid (BA) was provided, suggesting that SA can be synthesized from BA. Furthermore, despite the substantial accumulation of SA upon pathogen infection, we did not observe incorporation of 13 C label from Phe into SA. We also did not detect 13 C6 -SA in PAL-overexpressing lines in the kfb01 kfb02 kfb39 kfb50 background after being fed 13 C6 -Phe, although endogenous PAL levels were dramatically increased. Based on these combined results, we propose that SA biosynthesis is not from Phe in Arabidopsis. These results have important implications for our understanding of the SA biosynthetic pathway in land plants.

Reduced γ-glutamyl hydrolase activity likely contributes to high folate levels in Periyakulam-1 tomato.

Tomato cultivars show wide variation in nutraceutical folate in ripe fruits, yet the loci regulating folate levels in fruits remain unexplored. To decipher regulatory points, we compared two contrasting tomato cultivars: Periyakulam-1 (PKM-1) with high folate and Arka Vikas (AV) with low folate. The progression of ripening in PKM-1 was nearly similar to AV but had substantially lower ethylene emission. In parallel, the levels of phytohormones salicylic acid, ABA, and jasmonic acid were substantially lower than AV. The fruits of PKM-1 were metabolically distinct from AV, with upregulation of several amino acids. Consistent with higher °Brix, the red ripe fruits also showed upregulation of sugars and sugar-derived metabolites. In parallel with higher folate, PKM-1 fruits also had higher carotenoid levels, especially lycopene and β-carotene. The proteome analysis showed upregulation of carotenoid sequestration and folate metabolism-related proteins in PKM-1. The deglutamylation pathway mediated by γ-glutamyl hydrolase (GGH) was substantially reduced in PKM-1 at the red-ripe stage. The red-ripe fruits had reduced transcript levels of GGHs and lower GGH activity than AV. Conversely, the percent polyglutamylation of folate was much higher in PKM-1. Our analysis indicates the regulation of GGH activity as a potential target to elevate folate levels in tomato fruits.

ВЛИЯНИЕ ОБРАБОТКИ САЛИЦИЛОВОЙ КИСЛОТОЙ НА РАЗВИТИЕ ВИНОГРАДНЫХ САЖЕНЦЕВ

The studies were carried out to assess the biological and economic efficiency of foliar application of the phytohormone salicylic acid when growing grafted grape seedlings in open ground conditions. The work was carried out in the field of Rostov region in 2019-2021 according to generally accepted methods in viticulture. The soil cover of the plots is ordinary chernozem, carbonate, medium-thick, heavy loamy, on loess-like loams. The seedlings were grown in an open way with soil mulching with a black film, planting pattern 0.2 × 0.15 m. The experiment included 6 options: control (water); standard (urea - 4 g/l); salicylic acid - 0.5 mg/l; salicylic acid - 1.0 mg/l; salicylic acid - 1.5 mg/l; salicylic acid - 2.0 mg/l, in 3 replications of 300 vaccinations. The experiments were carried out on the varieties Cabernet Sauvignon, Denisovsky, Kumshatsky white. In the course of the study, biometric indicators of the development of the aerial part and the root system, the yield of standard seedlings were determined. The use of salicylic acid on all varieties stimulated the growth of shoots and leaf surface. In seedlings of Denisovsky variety, an increase in the diameter of the shoots by 0.2 ... 0.7 mm was noted, relative to the control. In seedlings of Cabernet Sauvignon variety, the number of roots exceeded the control by 3.4 ... 4.8 pieces, the standard - up to 1.2 pieces. There was a tendency to increase the number of roots in the Denisovsky variety, compared with the control, by 1.2 ... 2.8 pieces, significant differences with the standard were not found. The effect of salicylic acid treatment on the formation of the root system of seedlings of Kumshatsky white variety was the least pronounced, the largest excess over the control was 1.6 pcs. in the salicylic acid 0.5 mg/l variant, no significant differences with the standard were found. The highest yield of standard seedlings in Kumshatsky white variety was noted in the salicylic acid 0.5 mg/l variant - 62.8%, which is 11.3% higher than the control; Cabernet Sauvignon - salicylic acid 1.0 mg/l (73.3% and 9.0%, respectively); Denisovsky - salicylic acid 1.0 mg/l (44.6% and 5.3%).

Salicylic acid inhibits gibberellin signaling through receptor interactions

It is well known that plants activate defense responses at the cost of growth. However, the underlying molecular mechanisms are not well understood. The phytohormones salicylic acid (SA) and gibberellin (GA) promote defense response and growth, respectively. Here we show that SA inhibits GA signaling to repress plant growth. We found that the SA receptor NPR1 interacts with the GA receptor GID1. Further biochemical studies revealed that NPR1 functions as an adaptor of ubiquitin E3 ligase to promote the polyubiquitination and degradation of GID1, which enhances the stability of DELLA proteins, the negative regulators of GA signaling. Genetic analysis suggested that NPR1, GID1, and DELLA proteins are all required for the SA-mediated growth inhibition. Collectively, our study not only uncovers a novel regulatory mechanism of growth–defense trade-off but also reveals the interaction of hormone receptors as a new mode of hormonal crosstalk.

Salicylic acid and jasmonic acid crosstalk in plant immunity.

The phytohormones salicylic acid (SA) and jasmonic acid (JA) are major players in plant immunity. Numerous studies have provided evidence that SA- and JA-mediated signaling interact with each other (SA-JA crosstalk) to orchestrate plant immune responses against pathogens. At the same time, SA-JA crosstalk is often exploited by pathogens to promote their virulence. In this review, we summarize our current knowledge of molecular mechanisms for and modulations of SA-JA crosstalk during pathogen infection.

Bensulfuron-Methyl, Terbutylazine, and 2,4-D Butylate Disturb Plant Growth and Resistance by Deteriorating Rhizosphere Environment and Plant Secondary Metabolism in Wheat Seedlings

Frequent and improper use of herbicides disrupts a plant's metabolism, causing oxidative stress that degrades crop quality. However, few studies have examined the inhibitory effects of herbicides on plant growth and defense mechanisms in terms of their impact on soil quality and crop rhizosphere. Therefore, the current study investigated the detrimental impacts of six typical and multilevel herbicides on the microbial community and signal molecules in the soil as well as on the levels of hormones and secondary metabolites in wheat seedlings. Interestingly, bensulfuron-methyl, terbutylazine (TBA), and 2,4-D butylate significantly induced oxidative damage while reducing the number of phytohormones (salicylic acid and jasmonic acid) and secondary metabolites (tricin, quercetin, and caffeic acid) in the roots and leaves compared with the controls, isoproturon, fenoxaprop-p-ethyl, and pretilachlor. At twice the recommended levels (2×), they also decreased the microbial α diversity and, in particular, the abundance of Gammaproteobacteria, Alphaproteobacteria, Actinobacteria, Bacteroidia, Verrucomicrobia, Bacilli, Acidimicrobiia, Deltaproteobacteria, and Gemmatimonadetes by disrupting the level of enzymes (e.g., urease and sucrase) and metabolites (indole-3-acetic acid, salicylic acid, apigenin, 4-hydroxybenzoic acid, DIMBOA, and melatonin) in the rhizosphere soil. Overall, significant exposure to herbicides may inhibit wheat growth by disturbing the microbial composition in the rhizosphere soil and the distribution of secondary metabolites in wheat seedlings.

Manufactured Nano-Objects Confer Viral Protection against Cucurbit Chlorotic Yellows Virus (CCYV) Infecting Nicotiana benthamiana.

Nanotechnology has emerged as a new tool to combat phytopathogens in agricultural crops. Cucurbit chlorotic yellows virus (CCYV) mainly infects Solanaceae crops and causes significant crop losses. Nanomaterials (NMs) may have efficacy against plant viruses, but the mechanisms underlying complex nanomaterials-plant-virus interactions remain elusive. We challenged Nicotiana benthamiana plants with GFP-tagged CCYV and observed morphological, physiological, and molecular changes in response to 21-d foliar exposure to nanoscale Fe and Zn and C60 fullerenes at 100 mg/L concentration for 21 days. We observed that in response to C60 (100 mg/L) treatment, plants displayed a normal phenotype while the viral infection was not seen until 5 days post-inoculation. On the contrary, Fe and Zn were unable to suppress viral progression. The mRNA transcriptional analysis for GFP and viral coat protein revealed that the transcripts of both genes were 5-fold reduced in response to C60 treatment. Evaluation of the chloroplast ultrastructure showed that NMs treatment maintained the normal chloroplast structure in the plants as compared to untreated plants. C60 upregulated the defense-related phytohormones (abscisic acid and salicylic acid) by 42–43%. Our results demonstrate the protective function of carbon-based NMs, with suppression of CCYV symptoms via inhibition of viral replication and systemic movement.

Genome-Wide Characterization of Ascorbate Peroxidase Gene Family in Peanut (Arachis hypogea L.) Revealed Their Crucial Role in Growth and Multiple Stress Tolerance.

Ascorbate peroxidase (APX), an important antioxidant enzyme, plays a significant role in ROS scavenging by catalyzing the decrease of hydrogen peroxide under various environmental stresses. Nevertheless, information about the APX gene family and their evolutionary and functional attributes in peanut (Arachis hypogea L.) was not reported. Therefore, a comprehensive genome-wide study was performed to discover the APX genes in cultivated peanut genome. This study identified 166 AhAPX genes in the peanut genome, classified into 11 main groups. The gene duplication analysis showed that AhAPX genes had experienced segmental duplications and purifying selection pressure. Gene structure and motif investigation indicated that most of the AhAPX genes exhibited a comparatively well-preserved exon-intron pattern and motif configuration contained by the identical group. We discovered five phytohormones-, six abiotic stress-, and five growth and development-related cis-elements in the promoter regions of AhAPX. Fourteen putative ah-miRNAs from 12 families were identified, targeting 33 AhAPX genes. Furthermore, we identified 3,257 transcription factors from 38 families (including AP2, ARF, B3, bHLH, bZIP, ERF, MYB, NAC, WRKY, etc.) in 162 AhAPX genes. Gene ontology and KEGG enrichment analysis confirm the role of AhAPX genes in oxidoreductase activity, catalytic activity, cell junction, cellular response to stimulus and detoxification, biosynthesis of metabolites, and phenylpropanoid metabolism. Based on transcriptome datasets, some genes such as AhAPX4/7/17/77/82/86/130/133 and AhAPX160 showed significantly higher expression in diverse tissues/organs, i.e., flower, leaf, stem, roots, peg, testa, and cotyledon. Likewise, only a few genes, including AhAPX4/17/19/55/59/82/101/102/137 and AhAPX140, were significantly upregulated under abiotic (drought and cold), and phytohormones (ethylene, abscisic acid, paclobutrazol, brassinolide, and salicylic acid) treatments. qRT-PCR-based expression profiling presented the parallel expression trends as generated from transcriptome datasets. Our discoveries gave new visions into the evolution of APX genes and provided a base for further functional examinations of the AhAPX genes in peanut breeding programs.

Comprehensive In Silico Characterization and Expression Pro-Filing of DA1/DAR Family Genes in Brassica rapa.

The DA1/DAR family genes have been shown to play important roles in regulating organ size and plant biomass in the model plant Arabidopsis and several crops. However, this family has not been characterized in Brassica rapa (B. rapa). In this study, we identified 17 DA1&DAR genes from B. rapa. Phylogenetic analysis indicated that these genes are classified into four groups. Structural and motif analysis of BrDA1&DARs discovered that the genes within the same group have similar exon-intron structures and share an equal number of conserved motifs except for BrDAR6.3 from group IV, which contains two conserved motifs. Cis-regulatory elements identified four phytohormones (Salicylic acid, Abscisic acid, Gibberellin, and auxin) and three major abiotic (Light, Low temperature, and drought) responsive elements. Further, six br-miRNAs named br-miR164a, br-miR164b, br-miR164c, br-miR164d, br-miRN360, and br-miRN366 were found which target BrDAR6.1, BrDA1.4, and BrDA1.5. BrDA1&DAR genes were highly expressed in stem, root, silique, flower, leaf, and callus tissues. Moreover, qRT-PCR analyses indicated that some of these genes were responsive to abiotic stresses or phytohormone treatments. Our findings provide a foundation for further genetic and physiological studies of BrDA1&DARs in B. rapa.

Influence of exogenous phytohormone supplementation on the pigment and fatty acid content of three marine diatoms.

Diatoms are ubiquitous photosynthetic microorganisms with great potential for biotechnological applications. However, their commercialisation is hampered by production costs, requiring hence optimisation of cultivation methods. Phytohormones are plant growth regulators which may be used to influence physiological processes in microalgae, including diatoms. In this study, the model species Phaeodactylum tricornutum (Phaeodactylaceae) and two Irish isolates of Stauroneis sp. (Stauroneidaceae) and Nitzschia sp. (Bacillariaceae) were grown with varying amounts of the phytohormones indoleacetic acid (IAA), gibberellic acid (GA3), methyl jasmonate (MJ), abscisic acid (ABA) or salicylic acid (SA), and their influence on pigment and fatty acid profiles was monitored. The application of GA3 (200mg/l) stimulated the growth of P. tricornutum which accumulated 52% more dry biomass compared to the control and concomitantly returned the highest eicosapentaenoic acid (EPA) yield (0.6mg/l). The highest fucoxanthin yield (0.18mg/l) was obtained for P. tricornutum cultivated with GA3 (2mg/l) supplementation. In Stauroneis sp., SA (1mg/l) had the most positive effect on EPA, the content of which was enhanced up to 45.7μg/mg (4.6% of total dry weight). The SA (1mg/l) treatment also boosted carotenogenesis in Nitzschia sp., leading to 1.7- and 14-fold increases in fucoxanthin and β-carotene compared to the control, respectively. Of note, MJ (0.5mg/l) increased the EPA content of all diatom species compared to their controls. These results indicate that phytohormone-based treatments can be used to alter the pigment and lipid content of microalgae, which tend to respond in dose- and species-specific manners to individual compounds.Key points• Response to phytohormones was investigated in diatoms from distinct families.• MJ (0.5mg/l) caused an increase in EPA cellular content in all three diatoms.• Phytohormones mostly caused dose-dependent and species-specific responses.

Salicylic Acid Regulates Root Gravitropic Growth via Clathrin-Independent Endocytic Trafficking of PIN2 Auxin Transporter in Arabidopsis thaliana.

The phytohormone salicylic acid (SA) plays a crucial role in plant growth and development. However, the mechanism of high-concentration SA-affected gravitropic response in plant root growth and root hair development is still largely unclear. In this study, wild-type, pin2 mutant and various transgenic fluorescence marker lines of Arabidopsis thaliana were investigated to understand how root growth is affected by high SA treatment under gravitropic stress conditions. We found that exogenous SA application inhibited gravitropic root growth and root hair development in a dose-dependent manner. Further analyses using DIRECT REPEAT5 (DR5)-GFP, auxin sensor DII-VENUS, auxin efflux transporter PIN2-GFP, trans-Golgi network/early endosome (TGN/EE) clathrin-light-chain 2 (CLC2)-mCherry and prevacuolar compartment (PVC) (Rha1)-mCherry transgenic marker lines demonstrated that high SA treatment severely affected auxin accumulation, root-specific PIN2 distribution and PIN2 gene transcription and promoted the vacuolar degradation of PIN2, possibly independent of clathrin-mediated endocytic protein trafficking. Our findings proposed a new underlying mechanism of SA-affected gravitropic root growth and root hair development via the regulation of PIN2 gene transcription and PIN2 protein endocytosis in plants.

Investigation of Solanum carolinense Dominance and Phytotoxic Effect in Festuca arundinacea with Special Reference to Allelochemical Identification, Analysis of Phytohormones and Antioxidant Mechanisms

Exposure to invasive weeds in pasturelands may result in significant losses and toxicity in forage crops. These species may also contain a compound that may be toxic as well as beneficial depending upon the effect induced. The Ministry of Environment of the Republic of Korea has now recognized Solanum carolinense (Horsenettle)—an invasive weed species—as a potential threat to forage crops in pasturelands and to the entire agro-ecosystem. As a forage crop, Festuca arundinacea (Tall fescue) is one of the major economical crops and diets of livestock; in this study, the competition patterns of Solanum carolinense and Festuca arundinacea were examined with respect to their seeding ratios and growth periods. In addition, an extract from the root of Solanum carolinense (SCE) was prepared and treated at 2500 ppm and 5000 ppm in a Festuca arundinacea plant to observe its effect. The experimental results showed that as the growth period of the Horsenettle and the SCE treatment increased, the germination rate, plant height, root length, fresh weight, and dry weight of the tall fescue were significantly decreased. Moreover, the SCE treatment significantly increased the quantities of reactive oxygen species (O2− and H2O2), antioxidants (Catalase and Peroxidase), and endogenous phytohormones (Abscisic acid and Salicylic acid), and simultaneously decreased the superoxide dismutase content in the tall fescue shoots. Furthermore, we identified several glycoalkaloids from the SCE extract, among which Solanidan-3-ol, (3β,5α)’ possessed a higher number (52%). Based on these results, we predicted that the Solanidan-3-ol, (3β,5α)’ present in horsenettle has a major role in imposing phytotoxicity on agricultural crops. The glycoalkaloids in the Solanum species have been reported to possess both phytotoxic and therapeutic uses. Based on this concept, we believe that the compound available in Solanum carolinense could be used in developing crop protection or medicinal products through broader research. Conversely, our findings also showed the probable risk of horsenettle to the agro-ecosystem, especially in terms of forage production.

Phosphate Mobilization by Culturable Fungi and Their Capacity to Increase Soil P Availability and Promote Barley Growth.

Large-scale screening of 848 culturable soil and endophytic filamentous fungi and yeasts for the ability to mobilize inorganic and organic P compounds was performed. Five strains of filamentous fungi having the highest level of phosphate-mobilizing ability were selected: Penicillium bilaiae Pb14, P. bilaiae C11, P. rubens EF5, Talaromyces pinophilus T14, and Aspergillus sp. D1. These strains in vitro actively solubilized Ca, Al, and Fe phosphates and Ca phytate. The amount of mobilized P negatively correlated with pH of the medium and positively correlated with fungal biomass. The proposed mechanisms for P mobilization were acidification of the medium, organic acid release, and phosphatase activity. The fungi decreased pH of the medium from 7.0 to 2.3-5.0. Ten different organic acids were produced by fungi with pyruvic acid being a major component. Acid phosphatase activity varied from 0.12 EU to 0.84 EU, and alkaline phosphatase activity varied from 0.08 EU to 0.61 EU depending on the strain. Available P concentration in soil was increased by 13-28% after introduction of the fungi. The fungi also produced phytohormones auxins, salicylic acid, and abscisic acid. All the strains, except Aspergillus sp. D1, promoted elongation and increased biomass of barley seedlings grown in soil. Shoot P concentration increased by 17-26% after inoculation with P. bilaiae Pb14, T. pinophilus T14, and Aspergillus sp. D1. It was concluded that the selected fungal strains promoted plant growth due to P mobilization and phytohormone production.