Indole-3-acetic Acid Levels Research Articles

Characterization of phytohormone and transcriptome reprogramming profiles during maize early kernel development

BackgroundDuring maize early kernel development, the dramatic transcriptional reprogramming determines the rate of developmental progression, and phytohormone plays critical role in these important processes. To investigate the phytohormone levels and transcriptome reprogramming profiles during maize early kernel development, two maize inbreds with similar genetic background but different mature kernel sizes (ILa and ILb) were used.ResultsThe levels of indole-3-acetic acid (IAA) were increased continuously in maize kernels from 5 days after pollination (DAP) to 10 DAP. ILa had smaller mature kernels than ILb, and ILa kernels had significantly lower IAA levels and significantly higher SA levels than ILb at 10 DAP. The different phytohormone profiles correlated with different transcriptional reprogramming in the two kernels. The global transcriptomes in ILa and ILb kernels were strikingly different at 5 DAP, and their differences peaked at 8 DAP. Functional analysis showed that the biggest transcriptome difference between the two kernels is those response to biotic and abiotic stresses. Further analyses indicated that the start of dramatic transcriptional reprogramming and the onset of significantly enriched functional categories, especially the “plant hormone signal transduction” and “starch and sucrose metabolism”, was earlier in ILa than in ILb, whereas more significant enrichment of those functional categories occurred at later stage of kernel development in ILb.ConclusionsThese results indicate that later onset of the significantly enriched functional categories, coincide with their stronger activities at a later developmental stage and higher IAA level, are necessary for young kernels to undergo longer mitotic activity and finally develop a larger kernel size. The different onset times and complex interactions of the important functional categories, especially phytohormone signal, and carbohydrate metabolism, form the most important molecular regulators mediating maize early kernel development.

Increased endogenous indole-3-acetic acid:abscisic acid ratio is a reliable marker of Pinus massoniana rejuvenation

ABSTRACTPinus massoniana is a recalcitrant tree species for rooting in vitro. We rejuvenated 26-year-old P. massoniana trees by successive grafting. Rooting rates of rejuvenated shoots were > 83.1% after rooting induction. We compared endogenous levels of indole-3-acetic acid (IAA), abscisic acid (ABA), gibberellins (GAs) and zeatin-riboside (ZR), and the rhizogenesis ability of axillary shoots of mature and rejuvenated materials in vitro, i.e., somaplants and grafts. Enhancement of the rooting ability of mature materials in vitro following somatic embryogenesis or repeated grafting onto juvenile rootstocks was accompanied by increased IAA and GAs levels, and by decreased ABA levels in scions used as starting material for micropropagation in vitro. Successive subcultures did not influence the rooting ability of shoots from untreated mature material. Rooting ability of shoots in vitro, however, gradually increased with subculture frequency during repeated subculturing in grafting materials. The IAA:ABA ratio in shoots in vitro after grafting five times, and consequently capable of root organogenesis, was higher than in shoots of untreated mature material incapable of root organogenesis in vitro. A high IAA:ABA ratio was detected in scions of somaplants that were capable of rooting in vitro despite subculture times. We found that the endogenous IAA:ABA ratio is a reliable marker for the recovery of root organogenesis in vitro after rejuvenating treatments for mature P. massoniana trees.

Uremic Toxin Concentrations are Related to Residual Kidney Function in the Pediatric Hemodialysis Population.

Protein-bound uremic toxins (PBUTs) play a role in the multisystem disease that children on hemodialysis (HD) are facing, but little is known about their levels and protein binding (%PB). In this study, we evaluated the levels and %PB of six PBUTs cross-sectionally in a large pediatric HD cohort (n = 170) by comparing these with healthy and non-dialysis chronic kidney disease (CKD) stage 4–5 (n = 24) children. In parallel β2-microglobulin (β2M) and uric acid (UA) were evaluated. We then explored the impact of age and residual kidney function on uremic toxin levels and %PB using analysis of covariance and Spearman correlation coefficients (rs). We found higher levels of β2M, p-cresyl glucuronide (pCG), hippuric acid (HA), indole acetic acid (IAA), and indoxyl sulfate (IxS) in the HD compared to the CKD4–5 group. In the HD group, a positive correlation between age and pCG, HA, IxS, and pCS levels was shown. Residual urine volume was negatively correlated with levels of β2M, pCG, HA, IAA, IxS, and CMPF (rs −0.2 to −0.5). In addition, we found overall lower %PB of PBUTs in HD versus the CKD4–5 group, and showed an age-dependent increase in %PB of IAA, IxS, and pCS. Furhtermore, residual kidney function was overall positively correlated with %PB of PBUTs. In conclusion, residual kidney function and age contribute to PBUT levels and %PB in the pediatric HD population.

Global transcriptome analyses reveal that infection with chrysanthemum stunt viroid (CSVd) affects gene expression profile of chrysanthemum plants, but the genes involved in plant hormone metabolism and signaling may not be silencing target of CSVd-siRNAs

Abstracts Chrysanthemum stunt viroid (CSVd) is a pathogen that induces stunted plant growth as a typical disease symptom in infected chrysanthemum plants. Because of its simple RNA genomic structure, the mechanism of how CSVd provokes pathogenicity in host plants remains elusive. Since small RNAs generated from CSVd genomic RNA accumulated in infected plants ( Tsuro et al., 2013 ), it has been suggested that forced gene silencing against intrinsic genes by CSVd-small interfering (si)RNAs is involved in its pathogenicity. In this study, we revealed that CSVd infection induced global fluctuation of gene expression in plants. Hypothetical CSVd-siRNAs (22 nucleotides long) from (+) and (−) strands of the CSVd RNA genome were surveyed to examine if they could target the down-regulated gene sequences. Six genes were identified as target candidates, but the causal link between their functions and disease symptoms was remained unclear. In contrast, the expression levels of genes involved in the biosynthesis of gibberellic acid (GA) and cytokinin (CK), indole-3-acetic acid (IAA) transport and cell wall growth in infected plants were down-regulated, but mRNAs of those genes were not found as possible target sequences of CSVd-siRNAs. On the other hand, endogenous levels of GA, CK, IAA, and abscisic acid and the rate of IAA movement in the stem were not different between healthy and infected plants. Growth promotion of infected plants by GA treatment was poorer than that of healthy plants, suggesting that CSVd infection suppressed the GA-signaling pathway. This was further supported by the findings of a reduced response of GA-regulated genes to GA treatment and up-regulation of the DELLA-protein gene, a negative regulator of GA-signaling, in infected plants. Thus, the down-regulation of GA responsiveness and inhibition of cell wall expansion are major causes of the stunted growth of CSVd-infected chrysanthemum plants.

Alleviation of salt stress response in soybean plants with the endophytic bacterial isolate Curtobacterium sp. SAK1

Salinity has been a major abiotic stressor that reduce the productivity. Previous studies reported that endophytic bacteria produce plant stress response hormones, antioxidants, and enzymes such as ACC deaminase. Augmentation of these metabolites and enzymes by endophytes mitigates the stress effects of salinity and improves plant growth and productivity. Bacterial endophytes were isolated from Artemisia princeps Pamp, and evaluated for indole-3-acetic acid (IAA), abscisic acid (ABA), siderophore, and 1-aminocyclopropane-1-carboxylate (ACC) deaminase production and the ability to solubilize phosphate in the presence of NaCl (100–400 mM). SAK1 was applied to Glycine max cv. Pungsannamul to investigate salinity stress. Our results revealed that with an increase in NaCl concentration, the amount of ABA production in SAK1 increased, whereas IAA levels decreased. Bacterial ABA and JA degrade the reactive oxygen species and protect plants against stressors. Gas chromatography-mass spectrometry (GC-MS) analysis detected different gibberellins (GAs) and organic acids in SAK1. Interestingly, SAK1 inoculation significantly increased plant growth attributes under normal and salinity stress conditions, whereas a decrease in endogenous jasmonic acid and ABA content in the plants was recorded under salinity stress. IAA and GAs enhance number of root tips and hence improve nutrients uptake in plants. Polyphenolic oxidase and peroxidase were alleviated by elevated SAK1 in G. max plants under stress. ACC deaminase of SAK1 resulted deamination of ACC, up to 330 nmol α-ketobutyrate mg−1 h−1 which could be a major reason of ethylene reduction promoting plant growth. SAK1 relieved salinity stress in plants by producing different phytohormones, antioxidants, and ACC deaminase enzyme. SAK1 could be a new addition in batch of plant stress hormone-regulating endophytic bacteria that mitigates the effects of salt stress and promotes plant growth in G. max.

Exogenous application of glycine betaine improved water use efficiency in winter wheat (Triticum aestivum L.) via modulating photosynthetic efficiency and antioxidative capacity under conventional and limited irrigation conditions

Improving water use efficiency (WUE) is an important subject in agricultural irrigation for alleviating the scarcity of water resources in semiarid regions of the North China Plain. Moreover, glycine betaine (GB) is one of the most effective compatible solutes synthesized naturally in plants for enhancing stress tolerance under abiotic stress, but little information is available on the involvement of GB in regulating crop WUE under field conditions. This study was conducted to explore the role of exogenously applied GB in improving WUE and plant physiological and biochemical responses in winter wheat subjected to conventional or limited irrigation during the 2015–2016 and 2016–2017 growing seasons. Exogenous application of GB significantly enhanced antioxidant enzyme activities and reduced the accumulation of malondialdehyde and hydrogen peroxide under limited irrigation conditions. Furthermore, GB-treated plants maintained higher leaf relative water content and membrane stability, which led to higher chlorophyll content and gas exchange attributes for better intrinsic and instantaneous water use efficiencies compared to control plants under limited irrigation conditions. GB-treated plants had higher indole-acetic acid and zeatin riboside levels but lower ABA levels compared to control plants under conventional and limited irrigation conditions. Additionally, GB enhanced the grain filling rate and duration, grain number per spike, and final grain weight, which resulted in higher grain yield compared to the control. Interestingly, GB significantly improved the integrative and photosynthetic WUE under conventional and limited irrigation conditions, although GB treatment did not markedly affect total water consumption. These results suggest the involvement of GB in improving WUEs in winter wheat by modulating hormonal balance, membrane stability, photosynthetic performance and antioxidant systems to maintain higher grain yield under conventional and limited irrigation conditions.

Biosynthesis of IAA and its role as signal molecule in the phytopathogenic bacterium Pseudomonas savastanoi

The strains of Pseudomonas savastanoi are responsible for the formation of tumors or excrescences in the aerial parts of woody plants, belong to the Pseudomonas syringaecomplex and are classified in the pathovars savastanoi (Psv, olive), nerii (Psn, oleander), retacarpa (Psr, Spanish broom) and fraxini (Psf, ash). The production of indole‐3‐acetic acid (IAA) in Psv and Psn is a factor of pathogenicity essential for the correct development of tumors in olive and oleander. In addition, IAA has been described as a signaling molecule capable of modifying gene expression of other virulence factors, such as the type III and type VI secretion systems. Most strains of P. savastanoi produce IAA from tryptophan through the indole‐3‐acetamide pathway. However, the iaaMHoperon is not present in Psf and it is not frequent in other pathovars of the P. syringae complex. Previously, our research group showed that a Psv ΔiaaMH mutant drastically reduces IAA levels and does not induce olive tumors. This mutant produces an IAA concentration in culture supernatant similar to produce by strains of Psf and other strains of P. syringae lacking these genes. These results suggest that the existence of an alternative route of IAA biosynthesis in Pseudomonas. In order to identify an alternative route, a comparative genomic analysis of P. savastanoi and other strains in the P. syringae complex was carried out. Currently, Psv mutants have been constructed in genes potentially involved in the biosynthesis of IAA. Additionally, a metabolic analysis of indolic compounds has been conducted to determine possible intermediates of this route. Finally, we carried out a comparative transcriptomic analysis (RNAseq) of the wild type Psv and its mutant Psv ΔiaaMHand was determined the impact of the addition of exogenous IAA to cultures of P. savastanoi. In summary, this work aims to identify new routes of IAA biosynthesis in P. savastanoi and to study regulatory roles of the phytohormone, IAA, on the expression of other virulence factors in Pseudomonas.Support or Funding InformationAGL2017‐82492‐C2‐1‐R (MINECO‐FEDER)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Aryl Hydrocarbon Receptor and Uremic Toxins from the Gut Microbiota in Chronic Kidney Disease Patients: Is There a Relationship between Them?

Recent studies have suggested that uremic toxins such as indoxyl sulfate (IS) and indole-3-acetic acid (IAA) from the metabolism of the gut microbiota may be involved in the inflammatory signaling pathway in chronic kidney disease (CKD) patients through the activation of the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor. The objective of this study was to investigate the possible relationship between uremic toxins (IS and IAA) and AhR protein expression in CKD patients. A cross-sectional observational study involving 17 hemodialysis (HD) [11 men, 55.5 ± 11.7 years of age, 54.0 (25.5-136.0) months of HD, body mass index (BMI) of 25.8 ± 3.8 kg/m2] and 15 non-dialysis-dependent (NDD) CKD (8 men, 54.1 ± 18.2 years of age, glomerular filtration rate of 34.8 ± 21.0 mL/min/1.73 m2, BMI of 27.4 ± 5.0 kg/m2) patients was conducted. IS and IAA levels were measured by reversed-phase high-performance liquid chromatography, and the protein expression levels of AhR and nuclear factor κ B (NF-κB) were evaluated by a Western blot assay. There was no difference in the expression of either AhR or NF-κB in the patients, and as expected, uremic toxin levels were higher in HD patients than in NDD patients. In the overall analysis, AhR protein expression was positively associated with IAA plasma levels ( r = 0.4; p = 0.03) and NF-κB protein expression ( r = 0.62; p = 0.001). Although the role of AhR in inflammation and CVD in CKD patients is far from being completely understood, the association between IAA and AhR observed in this study suggests a possible role for uremic toxins in the cell signaling pathway involved in inflammation in CKD patients.

Overexpression of OsIAAGLU reveals a role for IAA-glucose conjugation in modulating rice plant architecture.

OsIAAGLU could catalyze the reaction of IAA with glucose to generate IAA-glucose. Overexpression of OsIAAGLU in rice resulted in altered rice shoot architecture and root gravitropism. The distribution and levels of indole-3-acetic acid (IAA) within plant tissues are well known to play vital roles in plant growth and development. An important mechanism of regulating free IAA levels in monocots is formation of IAA ester conjugates. In this study, a cytosol-localized protein encoded by the rice gene of indole-3-acetic acid glucosyltransferase (OsIAAGLU) was found to catalyze the reaction of free IAA with glucose to generate IAA-glucose. Expression of OsIAAGLU could be induced by IAA and NAA. The number of tillers and leaf angle was significantly increased with a concomitant decrease in plant height and panicle length in the transgenic rice lines overexpressing OsIAAGLU compared to the wild-type (WT) plants. Phenotypes of iaaglu mutants constructed using the CRISPR/Cas9 system had no obvious differences with WT plants. Furthermore, overexpression of OsIAAGLU resulted in reduced sensitivity to IAA/NAA and altered gravitropic response of the roots in the transgenic plants. Free IAA contents in the leaves, root tips, and lamina joint of OsIAAGLU-overexpressing transgenic lines were lower than those of WT plants. These results support that OsIAAGLU could play a regulatory role in IAA homeostasis and rice architecture.

The study of hormonal metabolism of Trincadeira and Syrah cultivars indicates new roles of salicylic acid, jasmonates, ABA and IAA during grape ripening and upon infection with Botrytis cinerea

Hormones play an important role in fruit ripening and in response to biotic stress. Nevertheless, analyses of hormonal profiling during plant development and defense are scarce. In this work, changes in hormonal metabolism in grapevine (Vitis vinifera) were compared between a susceptible (Trincadeira) and a tolerant (Syrah) variety during grape ripening and upon infection with Botrytis cinerea. Infection of grapes with the necrotrophic pathogen Botrytis cinerea leads to significant economic losses worldwide.Peppercorn-sized fruits were infected in the field and mock-treated and infected berries were collected at green, veraison and harvest stages for hormone analysis and targeted qPCR analysis of genes involved in hormonal metabolism and signaling. Results indicate a substantial reprogramming of hormonal metabolism during grape ripening and in response to fungal attack. Syrah and Trincadeira presented differences in the metabolism of abscisic acid (ABA), indole-3-acetic acid (IAA) and jasmonates during grape ripening that may be connected to fruit quality. On the other hand, high basal levels of salicylic acid (SA), jasmonates and IAA at an early stage of ripening, together with activated SA, jasmonates and IAA signaling, likely enable a fast defense response leading to grape resistance/ tolerance towards B. cinerea.The balance among the different phytohormones seems to depend on the ripening stage and on the intra-specific genetic background and may be fundamental in providing resistance or susceptibility. In addition, this study indicated the involvement of SA and IAA in defense against necrotrophic pathogens and gains insights into possible strategies for conventional breeding and/or gene editing aiming at improving grape quality and grape resistance against Botrytis cinerea.

Transcriptomics of cytokinin and auxin metabolism and signaling genes during seed maturation in dormant and non-dormant wheat genotypes

To gain insights into the roles of cytokinin (CK) and auxin in regulating dormancy during seed maturation in wheat, we examined changes in the levels of CK and indole-3-acetic acid (IAA) and expression patterns of their metabolism and signaling genes in embryonic and endospermic tissues of dormant and non-dormant genotypes. Seed maturation was associated with a decrease in the levels of isopentenyladenine in both tissues mainly via repression of the CK biosynthetic TaLOG genes. Differential embryonic trans-zeatin content and expression patterns of the CK related genes including TacZOG, TaGLU and TaARR12 between maturing seeds of the two genotypes implicate CK in the control of seed dormancy induction and maintenance. Seed maturation induced a decrease of IAA level in both tissues irrespective of genotype, and this appeared to be mediated by repression of specific IAA biosynthesis, transport and IAA-conjugate hydrolysis genes. The differential embryonic IAA content and expression pattern of the IAA biosynthetic gene TaAO during the early stage of seed maturation between the two genotypes imply the role of IAA in dormancy induction. It appears from our data that the expression of specific auxin signaling genes including TaRUB, TaAXR and TaARF mediate the role of auxin signaling in dormancy induction and maintenance during seed maturation in wheat.

Talaromyces trachyspermus, an endophyte from Withania somnifera with plant growth promoting attributes

The medicinal plant, Withania somnifera is attributed by valuable medicinal properties and is widely cultivated. It is a need to take care of this plant from synthetic agrochemicals that may be hazardous for health and environment. The aim of the present study was to isolate and screen the endophytic fungi of W. somnifera that have potential of plant growth promotion and antagonism against plant pathogens. In this study, 22 potential fungal endophytes comprising of species of Alternaria, Aspergillus, Fusarium, Nigrospora, Colletotrichum and Talaromyces identified at National Fungal Culture Collection of India (NFCCI), Pune were isolated. The potential isolate, Talaromyces trachyspermus was confirmed by BLAST and phylogenetic analysis of sequences of rDNA ITS, LSU (D1 D2) and β-tubulin genes. Among all the isolates, T. trachyspermus exhibited comparatively higher activity for hydrolytic enzymes, protease, chitinase, amylase, cellulase and pectinase that are required for antagonistic property. It was observed to be a promising biocontrol agent against plant pathogen, Sclerotinia sclerotiorum. This strain is also characterized with high level of indole acetic acid (IAA), siderophore synthesis, and phosphate solubilization activities that are important for plant growth promotion. This is the first report on endophyte, T. trachyspermus from W. somnifera having potential plant growth promoting traits and biocontrol, which can be further exploited to enhance the medicinal value of the plant.

Effects of Co-Inoculation of Indole-3-Acetic Acid-Producing and -Degrading Bacterial Endophytes on Plant Growth

Bacterial production of indole-3-acetic acid (IAA) and its effects on plant growth have been frequently studied but there have been few studies on the ecology of IAA-degrading bacteria. In this study, among eight endophytic bacterial strains previously isolated from the same sweet potato sample including two IAA producers, Klebsiella sp. Sal 1 and Enterobacter sp. Sal 3, all of the strains showed IAA-degrading ability to some extent. Herbaspirillum sp. Sal 6 had the highest activity for IAA and tryptophan. When the IAA producers and the degrader were co-cultured in tryptophan-amended N+MR liquid medium, the concentrations of IAA decreased. Inoculation with Klebsiella sp. Sal 1, the highest IAA producer among the test strains, increased fresh root weight of tomato and radish, but the effect decreased by co-inoculation with IAA-degrading Herbaspirillum sp. Sal 6. Since both strains colonized plant parts at high populations, it was likely that the IAA degrader decreased IAA levels in the plants by degrading IAA and/or its precursor tryptophan. When IAA-producing biofertilizers are used, interactions with IAA degraders in plants should be considered.

Enhancement of vitality and activity of a plant growth-promoting bacteria (PGPB) by atmospheric pressure non-thermal plasma

The inconsistent vitality and efficiency of plant growth promoting bacteria (PGPB) are technical limitations in the application of PGPB as biofertilizer. To improve these disadvantages, we examined the potential of micro Dielectric Barrier Discharge (DBD) plasma to enhance the vitality and functional activity of a PGPB, Bacillus subtilis CB-R05. Bacterial multiplication and motility were increased after plasma treatment, and the level of a protein involved in cell division was elevated in plasma treated bacteria. Rice seeds inoculated with plasma treated bacteria showed no significant change in germination, but growth and grain yield of rice plants were significantly enhanced. Rice seedlings infected with plasma treated bacteria showed elevated tolerance to fungal infection. SEM analysis demonstrated that plasma treated bacteria colonized more densely in the broader area of rice plant roots than untreated bacteria. The level of IAA (Indole-3-Acetic Acid) and SA (Salicylic Acid) hormone was higher in rice plants infected with plasma treated than with untreated bacteria. Our results suggest that plasma can accelerate bacterial growth and motility, possibly by increasing the related gene expression, and the increased bacterial vitality improves colonization within plant roots and elevates the level of phytohormones, leading to the enhancement of plant growth, yield, and tolerance to disease.

A leaf shape mutant provides insight into PINOID Serine/Threonine Kinase function in cucumber (Cucumis sativus L.)

Optimizing leaf shape is a major challenge in efforts to develop an ideal plant type. Cucumber leaf shapes are diverse; however, the molecular regulatory mechanisms underlying leaf shape formation are unknown. In this study, we obtained a round leaf mutant (rl) from an ethyl methanesulfonate-induced mutagenesis population. Genetic analysis revealed that a single recessive gene, rl, is responsible for this mutation. A modified MutMap analysis combined linkage mapping identified a single nucleotide polymorphism within a candidate gene, Csa1M537400, as the mutation underlying the trait. Csa1M537400 encodes a PINOID kinase protein involved in auxin transport. Expression of Csa1M537400 was significantly lower in the rl mutant than in wild type, and it displayed higher levels of IAA (indole-3-acetic acid) in several tissues. Treatment of wild-type plants with an auxin transport inhibitor induced the formation of round leaves, similar to those in the rl mutant. Altered expression patterns of several auxin-related genes in the rl mutant suggest that rl plays a key role in auxin biosynthesis, transport, and response in cucumber. These findings provide insight into the molecular mechanism underlying the regulation of auxin signaling pathways in cucumber, and will be valuable in the development of an ideal plant type.

Metabolic and proteomic alteration in phytohormone-producing endophytic Bacillus amyloliquefaciens RWL-1 during methanol utilization.

Methanol utilization by bacteria is important for various industrial processes. Methylotrophic bacteria are taxonomically diverse and some species promote plant growth and induce stress tolerance. However, methylotrophic potential of bacterial endophytes is poorly understood. The current study aimed to evaluate the metabolomic and proteomic changes in endophytic Bacillus amyloliquefaciens RWL-1 caused by its methanol utilization and the resultant influence on its phytohormone production. B. amyloliquefaciens RWL-1 was grown in LB medium with different concentrations [0 (control), 0.5, 1, 1.5, 2, 2.5, 3, 3.5, and 4%) of methanol to examine its methylotrophic potential. SDS-PAGE analysis was carried out for bacterial protein confirmation. Moreover, the phytohormones (indole 3 acetic acid (IAA), gibberellins (GAs), abscisic acid (ABA)) produced by RWL-1 in methanol supplemented medium were quantified by GC-MS/SIM (6890N Network GC system, and 5973 Network Mass Selective Detector; Agilent Technologies, Santa Clara, CA, USA), while the antioxidants were estimated spectrophotometrically (T60 UV-VIS spectrophotometer, Leicester, UK). The amino acid quantification was carried out by amino acid analyzer (HITACHI L-8900, Japan). Furthermore, Nano-liquid chromatography (LC)-MS/MS analysis was performed with an Agilent system (Wilmington, DE, USA) for proteomic analysis while mascot algorithm (Matrix science, USA) was used to identify peptide sequences present in the protein sequence database. RWL-1 showed significant growth in media supplemented with 2 and 3.5% methanol, when compared with other concentrations. Mass spectroscopy analysis revealed that RWL-1 utilizes methanol efficiently as a carbon source. In the presence of methanol, RWL-1 produced significantly higher levels of IAA but lower levels of ABA, when compared with the control. Further, enzymatic antioxidants and functional amino acids were significantly up-regulated, with predominant expression of glutamic acid and alanine. Nano-liquid chromatography, quadrupole time-of-flight analysis, and quantitative analysis of methanol-treated bacterial cells showed expression of eight different types of proteins, including detoxification proteins, unrecognized and unclassified enzymes with antioxidant properties, proteases, metabolism enzymes, ribosomal proteins, antioxidant proteins, chaperones, and heat shock proteins. Results demonstrate that RWL-1 can significantly enhance its growth by utilizing methanol, and could produce phytohormones when growing in methanol-supplemented media, with increased expression of specific proteins and different biochemicals. These results will be useful in devising strategies for utilizing methylotrophic bacterial endophytes as alternative promoters of plant growth. Understanding RWL-1 ability to utilize methanol. The survival and phytohormones production by Bacillus amyloliquefaciens RWL-1 in methanol supplemented media whistle inducing metabolic and proteomic changes.

Mechanisms of the IAA and ACC-deaminase producing strain of Trichoderma longibrachiatum T6 in enhancing wheat seedling tolerance to NaCl stress

BackgroundTrichoderma species, a class of plant beneficial fungi, may provide opportunistic symbionts to induce plant tolerance to abiotic stresses. Here, we determined the possible mechanisms responsible for the indole acetic acid (IAA) and 1-aminocyclopropane-1-carboxylate-deaminase (ACC-deaminase) producing strain of Trichoderma longibrachiatum T6 (TL-6) in promoting wheat (Triticum aestivum L.) growth and enhancing plant tolerance to NaCl stress.ResultsWheat treated with or without TL-6 was grown under different levels of salt stress in controlled environmental conditions. TL-6 showed a high level of tolerance to 10 mg ml− 1 of NaCl stress and the inhibitory effect was more pronounced at higher NaCl concentrations. Under NaCl stress, the activity of ACC-deaminase and IAA concentration in TL-6 were promoted, with the activity of ACC-deaminase increased by 26% at the salt concentration of 10 mg ml− 1 and 31% at 20 mg ml− 1, compared with non-saline stress; and the concentration of IAA was increased by 10 and 7%, respectively (P < 0.05). The increased ACC-deaminase and IAA concentration in the TL-6 strain may serve as an important signal to alleviate the negative effect of NaCl stress on wheat growth. As such, wheat seedlings with the ACC-deaminase and IAA producing strain of TL-6 treatment under NaCl stress increased the IAA concentration by an average of 11%, decreased the activity of ACC oxidase (ACO) by an average of 12% and ACC synthase (ACS) 13%, and decreased the level of ethylene synthesis and the content of ACC by 12 and 22%, respectively (P < 0.05). The TL-6 treatment decreased the transcriptional level of ethylene synthesis genes expression, and increased the IAA production genes expression significantly in wheat seedlings roots; down-regulated the expression of ACO genes by an average of 9% and ACS genes 12%, whereas up-regulated the expression of IAA genes by 10% (P < 0.05). TL-6 treatments under NaCl stress decreased the level of Na+ accumulation; and increased the uptake of K+ and the ratio of K+/Na+, and the transcriptional level of Na+/H+ antiporter gene expression in both shoots and roots.ConclusionsOur results indicate that the strain of TL-6 effectively promoted wheat growth and enhanced plant tolerance to NaCl stress through the increased ACC-deaminase activity and IAA production in TL-6 stain that modulate the IAA and ethylene synthesis, and regulate the transcriptional levels of IAA and ethylene synthesis genes expression in wheat seedling roots under salt stress, and minimize ionic toxicity by disturbing the intracellular ionic homeostasis in the plant cells. These biochemical, physiological and molecular responses helped promote the wheat seedling growth and enhanced plant tolerance to salt stress.

Expression of BpPIN is associated with IAA levels and the formation of lobed leaves in Betula pendula ‘Dalecartica’

Auxin polar transport genes PIN (PIN-FORMED) determine the concentration gradient of auxin in plants. To understand the relationship between the development of different tissues in Betula pendula ‘Dalecartica’, BpPIN gene expression and indole-3-acetic acid (IAA) content were analyzed using qRT-PCR, ELISA, and GUS staining. Gene expression of BpPIN genes and IAA levels in the leaves, buds, stems, xylem, and roots of B. pendula ‘Dalecartica’ and B. pendula as a control were measured. BpPIN1, BpPIN5 and BpPIN6 were upregulated during development in both species, suggesting a dominant role in the development of B. pendula ‘Dalecartica’ leaves. Moreover, BpPIN1 gene expression was positively associated with IAA levels during leaf, vein and petiole development in B. pendula ‘Dalecartica’ only. The correlation coefficient of the first three leaves was 0.69 (P = 0.04), while that of the first three petioles was 0.85 (P = 0.001). In addition, GUS staining of the pro-DR5::GUS transgenic line of cultivar was correlated with the results of BpPIN1 expression. Overall, these findings suggest that BpPIN1 is associated with the formation of lobed leaves in B. pendula ‘Dalecartica’.

Alleviation of drought stress in grapevine by foliar-applied strigolactones

Drought is one of the major abiotic stress factors that affect grape growth and yield, which in turn negatively affects the grape and wine production industry. Developing effective approaches to improve grapevine tolerance to drought stress is a priority for viticulture. Strigolactones, a newly discovered class of carotenoid-derived phytohormones, have been found to participate in various physiological processes. Herein, the effect of strigolactones (SLs) on grape seedlings under drought stress was investigated. Two-year-old grape seedlings (Vitis vinifera L.) were sprayed with 3 doses of rac-GR24 (1 μM, 3 μM and 5 μM), a synthesized strigolactone, and then were subjected to 7% (w/v) polyethylene glycol (PEG-6000) to simulate the drought conditions. Synthetic GR24 treated plants showed higher tolerance to drought stress with regard to lower electrolyte leakage, stomatal opening, reactive oxygen species (ROS), and higher relative water content, chlorophyll content, photosynthesis rate and malondialdehyde (MDA) content. GR24 application also decreased the levels of indoleacetic acid (IAA) and zeatin riboside (ZR), while increasing the level of abscisic acid (ABA), both in the roots and leaves under drought stress. These results suggested that foliar application of GR24 could ameliorate the adverse effects of drought due to its regulation of stomatal closure through ABA or ROS, and modulation of chlorophyll components and photosynthesis, as well as activation of the antioxidant defense capacity. Cross-talk with other hormones, especially ABA, was also suggested to be one of the important mechanism during this process. This study contributes to our current understanding of GR24-induced drought tolerance in grapevines.

Bacteria engineered to produce IL-22 in intestine induce expression of REG3G to reduce ethanol-induced liver disease in mice.

Antimicrobial C-type lectin regenerating islet-derived 3 gamma (REG3G) is suppressed in the small intestine during chronic ethanol feeding. Our aim was to determine the mechanism that underlies REG3G suppression during experimental alcoholic liver disease. Interleukin 22 (IL-22) regulates expression of REG3G. Therefore, we investigated the role of IL-22 in mice subjected to chronic-binge ethanol feeding (NIAAA model). In a mouse model of alcoholic liver disease, we found that type 3 innate lymphoid cells produce lower levels of IL-22. Reduced IL-22 production was the result of ethanol-induced dysbiosis and lower intestinal levels of indole-3-acetic acid (IAA), a microbiota-derived ligand of the aryl hydrocarbon receptor (AHR), which regulates expression of IL-22. Importantly, faecal levels of IAA were also found to be lower in patients with alcoholic hepatitis compared with healthy controls. Supplementation to restore intestinal levels of IAA protected mice from ethanol-induced steatohepatitis by inducing intestinal expression of IL-22 and REG3G, which prevented translocation of bacteria to liver. We engineered Lactobacillus reuteri to produce IL-22 (L. reuteri/IL-22) and fed them to mice along with the ethanol diet; these mice had reduced liver damage, inflammation and bacterial translocation to the liver compared with mice fed an isogenic control strain and upregulated expression of REG3G in intestine. However, L. reuteri/IL-22 did not reduce ethanol-induced liver disease in Reg3g-/- mice. Ethanol-associated dysbiosis reduces levels of IAA and activation of the AHR to decrease expression of IL-22 in the intestine, leading to reduced expression of REG3G; this results in bacterial translocation to the liver and steatohepatitis. Bacteria engineered to produce IL-22 induce expression of REG3G to reduce ethanol-induced steatohepatitis.