Synthesis Of IAA Research Articles

Auxin as a downstream signal positively participates in melatonin-mediated chilling tolerance of cucumber.

Here, we elucidate the interaction between IAA and melatonin (MT) in response to chilling in cucumber. The results showed that chilling stress induced the increase of endogenous MT and IAA, and the application of MT promoted the synthesis of IAA, while IAA could not affect endogenous MT content under chilling stress. Moreover, MT and IAA application both remarkably increased the chilling tolerance of cucumber seedlings in terms of lower contents of MDA and ROS, higher mRNA abundance of cold response genes, net photosynthetic rate (Pn), maximum regeneration rate of ribulose-1,5-diphosphate (Jmax), Rubisco maximum carboxylation efficiency (Vcmax), the activities and gene expression of RCA and Rubisco, as well as the content of active P700 (I/I0) and photosynthetic electron transport, compared with the plants in H2O treatment. Further analysis revealed that the inhibition of IAA transportation significantly reduced the chilling tolerance induced by MT, whereas the inhibition of endogenous MT did not affect the chilling tolerance induced by IAA. Meanwhile, we found that overexpression of the MT biosynthesis gene CsASMT increased the chilling tolerance, which was blocked by inhibition of endogenous IAA, and the silence of IAA biosynthesis gene CsYUCCA10 decreased the chilling tolerance of cucumber, which could not be alleviated by MT. These data implied IAA acted as a downstream signal to participate in the MT-induced chilling tolerance of cucumber seedlings. The study has implications for the production of greenhouse cucumber in winter seasons.

The micro-ecological feature of colonies is a potential strategy for Phaeocystis globosa bloom formation

Phaeocystis globosa is among the dominant microalgae associated with harmful algal blooms. P. globosa has a polymorphic life cycle and its ecological success has been attributed to algal colony formation, however, few studies have assessed differences in microbial communities and their functional profiles between intra- and extra-colonies during P. globosa blooms. To address this, environmental and metagenomics tools were used to conduct a time-series analysis of the bacterial composition and metabolic characteristics of intra- and extra-colonies during a natural P. globosa bloom. The results show that bacterial composition, biodiversity, and network interactions differed significantly between intra- and extra-colonies. Dominant extra-colonial bacteria were Bacteroidia and Saccharimonadis, while dominant intra-colonial bacteria included Alphaproteobacteria and Gammaproteobacteria. Despite the lower richness and diversity observed in the intra-colonial bacterial community, relative to extra-colonies, the complexity and interconnectedness of the intra-colonial networks were higher. Regarding bacterial function, more functional genes were enriched in substance metabolism (polysaccharides, iron element and dimethylsulfoniopropionate) and signal communication (quorum sensing, indoleacetic acid-IAA) pathways in intra- than in extra-colonies. Conceptual model construction showed that microbial cooperative synthesis of ammonium, vitamin B12, IAA, and siderophores were strongly related to the P. globosa bloom, particularly in the intra-colonial environment. Overall, our data highlight the differences in bacterial structure and functions within and outside the colony during P. globosa blooms. These findings represent fundamental information indicating that phenotypic heterogeneity is a selective strategy that improves microbial population competitiveness and environmental adaptation, benefiting P. globosa bloom formation and persistence.

Selenite reduced cadmium uptake, interfered signal transduction of endogenous phytohormones, and stimulated secretion of tartaric acid based on a combined analysis of non-invasive micro-test technique, transcriptome and metabolome

Selenium (Se) can reduce uptake and translocation of cadmium (Cd) in plants via plenty of ways, including regulation of root morphology. However, the underlying mechanisms on how Se will regulate root morphology under metal(loid) stresses are not fully illustrated. To fill up this knowledge gap, we investigated the effects of 0.5 mg L−1 selenite (Se(IV)) on root exudates, root morphology, root endogenous hormones, and Cd uptake efficiency of rice under the 1 mg L−1 Cd stress condition. The results showed that Se(IV) significantly reduced shoot and root Cd concentrations, and decreased Cd uptake efficiency via root hairs determined by a non–invasive micro-test (NMT) technology. When compared to the 1 mg L−1 Cd (Cd1) treatment, addition of 0.5 mg L−1 Se(IV) (1) significantly reduced root surface area and tip numbers, and non–significantly reduced root length, but significantly enhanced root diameter and root volume; (2) significantly enhanced concentrations of tartaric acid in the root exudate solution, root auxin (IAA) and root jasmonic acid (JA) via a UHPLC or a HPLC analysis; (3) significantly up-regulated metabolites correlated with synthesis of IAA, JA, gibberellin (GA), and salicylic acid, such as GA53, M–SA, (+/−)7–epi–JA, and derivatives of tryptophan and indole in the metabolome analysis. However, results of transcriptome analysis showed that (1) no upregulated differentially expressed genes (DEGs) were enriched in IAA synthesis; (2) some upregulated DEGs were found to be enriched in JA and GA53 synthesis pathways. In summary, although Se(IV) stimulated the synthesis of IAA, JA, and GA53, it significantly inhibited root growth mainly by 1) affecting signal transduction of IAA and GA; 2) altering IAA polar transport and homeostasis; and 3) regulating DEGs including SAUR32, SAUR36, SAUR76, OsSub33, OsEXPA8, OsEXPA18, and Os6bglu24.

The Relationship between Endogenous Hormone Content and Related Gene Expression and Tillering in Wild Kentucky Bluegrass

Poa pratensis is widely distributed in cold temperate regions and can be used as a species for stress restoration and as a forage for livestock. Studying the genetic characteristics of tillering occurrence in bluegrass provides a theoretical basis for studying plant yield formation, environmental adaptation, and improving survival competitiveness. The regulating effects of endogenous hormone IAA content and the expression of related genes ARF1, ARF12, ARF14, ZT content and the expression of related genes CKX2, CKX3, CKX4, SL content and the expression of related genes D14-like, D14.1-like and D14 in wild Kentucky bluegrass were investigated. Kentucky bluegrass from Sunan and Qingshui was used to evaluate the influence of hormone and gene expression on tillering behavior. Endogenous hormone contents and expression levels of related genes in stems and roots of both materials were measured at prophase, peak, and anaphase of tillering. The results showed that among the three materials, the Sunan material had a better tillering ability for Poa pratensis, while the Qingshui material had poorer tillering ability. The downregulation of CKX2, CKX3, and CKX4 gene expression levels promotes the synthesis of ZT, thereby improving the tillering ability of the germplasm. Upregulation of ARF14, D14, and D14.1-like gene expression levels enhances the synthesis of IAA and SL, thereby inhibiting tillering. More importantly, the interaction between hormones affects the tillering ability of bluegrass, and high levels of ZT/IAA, ZT/SL, and ZT/(IAA+SL) values promote tillering. In summary, this study reveals the mechanism by which hormones regulate the occurrence of tillering in Kentucky bluegrass, providing a theoretical basis for understanding the genetic characteristics of plant type, effectively regulating tillering, studying yield development, environmental adaptation, and improving survival rate.

Biocontrol mechanisms of Bacillus velezensis against Fusarium oxysporum from Panax ginseng

Root rot caused by Fusarium oxysporum severely reduces ginseng root yield and quality, leading to large economic losses. Biological control has attracted extensive attention because it is safe, environmentally friendly, and sustainable. Screening for biocontrol strains to suppress soil-borne diseases is important for improving ginseng quality. A Bacillus velezensis strain was isolated from the forest rhizosphere of Pinus sylvestris could inhibited F. oxysporum in ginseng. To explore the strain’s biocontrol effects and mechanism of action against F. oxysporum, four treatments were established in pot experiments: no inoculation (CK), F. oxysporum inoculation (F), B. velezensis YW 17 (B), and mixed inoculation of B. velezensis and F. oxysporum (BF). After 4 months of cultivation, the ginseng plants in the F treatment grew more slowly, and the withering degree was most serious among all the treatments. The results from high-throughput sequencing showed that the relative abundance of Fusarium in the roots of the BF treatment was significantly lower than that of the F treatment. B. velezensis inoculation improved the relative abundance of other beneficial microorganisms in the ginseng rhizosphere, such as Arthrobacter and Mortierella. The experimental results indicated that YW17 had strong abilities to produce biofilms and IAA, and could colonize roots. The whole genome sequencing results showed that some genes (trpA-C, gatA) were involved in the synthesis of the plant growth-promoting hormone IAA and other genes (efp, hfq, epsA-O, spo0A, sinI/sinR, lysC, yjbB, flgK, fliD, srfABC) were involved in biofilm formation and root colonization. The results of whole genome sequencing showed that there are 18 gene clusters related to the synthesis of secondary metabolite with antifungal activities. In addition, some genes involved in the biosynthetic pathway of acetoin, such as ilvB and alsD, were also found. Based on the above results, we infer that B. velezensis YW17 could inhibit pathogenic F. oxysporum by secreting antifungal lipopeptides, proteins and volatile substances, thereby indirectly protecting ginseng from pathogenic fungal infections. These results indicated that B. velezensis could control ginseng root rot indirectly by regulating the root and rhizosphere microbial community structures and directly by secreting antifungal substances.

Effects of Sphingobium yanoikuyae SJTF8 on Rice (Oryza sativa) Seed Germination and Root Development

The interaction between plant roots and rhizobacterium communities plays a crucial role in sustainable agriculture. We aimed to assess the effects of Sphingobium yanoikuyae SJTF8 on rice seed germination and development, as well as to observe the effects of different concentrations of S. yanoikuyae SJTF8 on the root systems of rice seedlings. The bacteria are best known for their role in the bioremediation and biodegradation of pollutants, and thus far, there is research that supports their agricultural prospects. The experiment comprised five different S. yanoikuyae SJTF8 concentrations: SP-y 8 (108 CFU/mL); SP-y 7 (107 CFU/mL); SP-y 6 (106 CFU/mL); SP-y 5 (105 CFU/mL); SP-y 4 (104 CFU/mL). We used sterilized water as the control treatment. The bacteria triggered the synthesis of IAA, while the seedling root lengths substantially increased on the 12th day after germination. The high application concentrations of S. yanoikuyae SJTF8 resulted in higher IAA production (with the SP-y 7 and SP-y 8 concentrations ranging from 151,029 pg/mL to 168,033 pg/mL). We found that the appropriate concentrations of S. yanoikuyae SJTF8 when applied as an inoculant were SP-y 7 and SP-y 6, based on the increased root growth and biomass production. The bacteria were also able to solubilize phosphorous. The growth response from the rice seedlings when inoculated with S. yanoikuyae SJTF8 presents the potential of the bacteria as a growth promotor. Its application in rice cultivation could be a sustainable approach to rice production.

Genome- and transcriptome-wide identification and analysis of B3 superfamily members and their association with salt stress response in the common bean (Phaseolus vulgaris L)

The plant-specific transcription factor B3 superfamily members mediate plant growth, development, and stress response. Although the B3 gene has been studied in various plants, its role in the common bean (Phaseolus vulgaris L) is unknown. In this study, 110 PvB3 genes were identified from the common bean genome and analyzed based on the phylogeny, gene structure, motifs, cis-regulatory elements, collinearity, and Ka/Ks. PvB3s were divided into four subgroups based on motifs and gene structure. The cis-element composition of the most PvB3 were involved in hormone production, abiotic stress response, and germination. Most PvB3 were highly expressed in the vigorously growth tissue of common bean, such as nodules, young pods, and young trifoliate. Moreover, RNA-seq results showed that PvB3-001/010/027/032/047/048/059/090 were enriched in tryptophan metabolism pathway (involves in AUX/IAA, GH3, and SAUR) of common bean under salt stress. Notably, exogenous IAA treatment could increase endogenous IAA content and the number of lateral roots, while altering the expression level of PvB3s in salt-sensitive common bean variety under salt stress. Taken together, the result indicated that PvB3 transcription factors may be involved in common bean salt stress response by participating in the synthesis and metabolic regulation of IAA. This study provides a theoretical basis for further study on the role of PvB3s in common bean abiotic stresses response.

The roles of strigolactones: Mineral compounds, indole-3 acetic acid and GA3 content in grapevine on drought stress

Plants have an extremely important place in the life of living creatures and in the ecological cycle. First of all, they undertake a complex phenomenon such as photosynthesis and perform critical tasks such as being raw material for different industrial branches especially for human and animal nutrition, preventing erosion, contributing to the soil in terms of organic matter, and assuring temperature control. It is also known that the environmental conditions of plants, which have such a significant place in our lives are changing day by day and the plants are faced with a vast number of adverse factors. Plants are affected by these factors of biotic or abiotic origin, which are not suitable for them, and as a consequence, they get stressed. Drought is the leading one of these stress factors. It is clearly acknowledged that endogenous hormones play a major role in the expression of plants as sensitive or tolerant as a result of responses to different types of stresses. It is known that some other substances such as jasmonates, brassinosteroids, salicylic acid and nitric oxide have been included in the endogenous hormones, which were examined under five basic groups until recently, namely auxin, gibberellin, cytokinin, abscisic acid and ethylene. One of these hormones derived from carotenoids is strigolactones (SL). Recent studies demonstrate that this substance produced in plant roots is also at the forefront in terms of stress tolerance. In this study, the effect of SL applications on drought resistance was investigated in Kober 5 BB and 110 R American grapevine rootstocks with different drought tolerance. Rootstocks were treated with 5 and 10 µM SL and exposed to drought stress. In order to measure the effects of SLs on stress, some physical (shoot length, shoot weight, average number of leaves per shoot) and biochemical (mineral substance and endogenous hormones) analysis were carried out. In the study, it was determined that SLs are a sort of hormone that has positive effects in terms of plant growth and development, promotes plant mineral nutrition, and that there is a positive relationship between the synthesis of the endogenous hormones IAA and GA3. According to the results obtained, it is comprehended that SLs can be used as growth regulators to alleviate drought stress.

Extending the benefits of PGPR to bioremediation of nitrile pollution in crop lands for enhancing crop productivity

Incessant release of nitrile group of compounds such as cyanides into agricultural land through industrial effluents and excessive use of nitrile pesticides has resulted in increased nitrile pollution. Release of nitrile compounds (NCs) as plant root exudates is also contributing to the problem. The released NCs interact with soil elements and persists for a long time. Persistent higher concentration of NCs in soil cause toxicity to beneficial microflora and affect crop productivity. The NCs can cause more problems to human health if they reach groundwater and enter the food chain. Nitrile degradation by soil bacteria can be a solution to the problem if thoroughly exploited. However, the impact of such bacteria in plant and soil environments is still not properly explored. Plant growth-promoting rhizobacteria (PGPR) with nitrilase activity has recently gained attention as potential solution to address the problem. This paper reviews the core issue of nitrile pollution in soil and the prospects of application of nitrile degrading bacteria for soil remediation, soil health improvement and plant growth promotion in nitrile-polluted soils. The possible mechanisms of PGPR that can be exploited to degrade NCs, converting them into plant useful compounds and synthesis of the phytohormone IAA from degraded NCs are also discussed at length.

The Growth-Promoting Mechanism of Brevibacillus laterosporus AMCC100017 on Apple Rootstock Malus robusta

Plant growth-promoting rhizobacteria (PGPR) located in rhizobacteria soil are beneficial to plant growth and development. A PGPR strain AMCC100017 of Brevibacillus laterosporus synthesizes the plant hormone IAA in a tryptophan-dependent manner. In this study, the AMCC100017 strain was used to treat Malus robusta , an excellent natural rootstock for apple production, and assess its ability to promote growth. The fresh weight, dry weight, plant height, and lateral root growth of M. robusta were significantly increased with treatment. The presence of the AMCC100017 strain increased IAA content in M. robusta and promoted root secretion of tryptophan. Colonization of the strain in the roots allowed continuous synthesis of IAA and promoted plant growth. In addition, the photosynthetic efficiency in leaves increased after microbial treatment, and the utilization of nitrogen, zinc, iron, copper and magnesium in leaves was increased, which was conducive to photosynthesis. Interestingly, the activities of CAT and SOD, as well as the contents of ROS in plants colonized by AMCC100017 were increased compared to control plants, but the activities of POD and MDA contents were decreased. AMCC100017 strain affected the antioxidant capacity and stress resistance of plants. AMCC100017 strain increased the content of soluble protein and soluble sugar in plants, improved plant metabolic activity and stress resistance. Therefore, AMCC100017 not only increased IAA content and photosynthetic efficiency to promote M. robusta growth, but also affected plant through multiple metabolic pathways.

Zinc application after low temperature stress promoted rice tillers recovery: Aspects of nutrient absorption and plant hormone regulation

Low temperature during the vegetative stage depresses rice tillering. Zinc (Zn) can promote rice tiller growth and improve plant resistance to abiotic stress. Consequently, Zn application after low temperature might be an effective approach to promote rice tiller recovery. A water culture experiment with treatments of two temperatures (12 °C and 20 °C) and three Zn concentrations (0.08 μM, 0.15 μM and 0.31 μM ZnSO4·7H2O) was conducted to determine by analyzing rice tiller growth, nutrient absorption and hormones metabolism. The results showed that low temperature reduced rice tiller numbers and leaf age, decreased as well. Increasing Zn application after low temperature could enhance not only rice tiller growth rate but also N metabolism and tillering recovery, and correlation analysis showed a significantly positive correlation between tiller increment and Zn and N accumulation after low temperature. In addition, higher cytokinin (CTK)/auxin (IAA) ratio was maintained by promoted synthesis of CTK and IAA as well as enhanced IAA transportation from tiller buds to other parts with increased Zn application after cold stress, which resulted in accelerated germination and growth of tiller buds. These results highlighted that Zn application after low temperature promoted rice tiller recovery by increasing N and Zn accumulation and maintaining hormones balance.

Isolation screening and molecular characterization of zinc solubilizing bacteria and their effect on the growth of wheat (Triticum aestivum)

Wheat (Triticum aestivum) is a major cereal crop grown worldwide. Most of the world population depends on wheat for their nutrient requirement. Zinc (Zn) is one of the most crucial elements required for the development of wheat plant. It is one of the micronutrients required in many biochemical cycles. It has been found that the concentration of Zn is below the required level in the soil and hence it remains deficient in the crops. To ameliorate the deficit, chemical fertilizers are added in the soil, where as biofertilizers are preferred over chemicals in sustainable agriculture. The paper describes the isolation, screening and molecular characterization of the zinc solubilizing bacteria (ZSB) to improve plant growth. A total of 100 soil samples were collected from the rhizospheric soil of wheat plants. ZSB were isolated by dilution plating on Bunt and Rovira media. The 50 isolates were selected and screened for their Zn solubilization. The zinc tolerance of all the isolates varied from 0.5% to 2% of insoluble Zn. Based on the Zn tolerance ability, 15 bacterial isolates were screened for Phosphate solubilization and further analyzed for the synthesis of IAA, NH3, siderophore production and chitinase activity. The three isolates were selected on the basis of the plant growth promoting characteristics for molecular characterization and were found to be homologous to Bacillus cereus, Pseudomonas aeruginosa and Bacillus tropicus. This study documented the establishment and survival of ZSB in the wheat rhizosphere and enhanced plant productivity, thus indicating the potential of isolates as commercial biofertilizers.

Anthocyanin accumulation correlates with hormones in the fruit skin of \u2018Red Delicious\u2019 and its four generation bud sport mutants

BackgroundBud sport mutants of apple (Malus domestica Borkh.) trees with a highly blushed colouring pattern are mainly caused by the accumulation of anthocyanins in the fruit skin. Hormones are important factors modulating anthocyanin accumulation. However, a good understanding of the interplay between hormones and anthocyanin synthesis in apples, especially in mutants at the molecular level, remains elusive. Here, physiological and comparative transcriptome approaches were used to reveal the molecular basis of color pigmentation in the skin of ‘Red Delicious’ (G0) and its mutants, including ‘Starking Red’ (G1), ‘Starkrimson’ (G2), ‘Campbell Redchief’ (G3) and ‘Vallee spur’ (G4).ResultsPigmentation in the skin gradually proliferated from G0 to G4. The anthocyanin content was higher in the mutants than in ‘Red Delicious’. The activation of early phenylpropanoid biosynthesis genes, including ASP3, PAL, 4CL, PER, CHS, CYP98A and F3’H, was more responsible for anthocyanin accumulation in mutants at the color break stage. In addition, IAA and ABA had a positive regulatory effect on the synthesis of anthocyanins, while GA had the reverse effect. The down-regulation of AACT1, HMGS, HMGR, MVK, MVD2, IDI1 and FPPS2 involved in terpenoid biosynthesis influences anthocyanin accumulation by positively regulating transcripts of AUX1 and SAUR that contribute to the synthesis of IAA, GID2 to GA, PP2C and SnRK2 to ABA. Furthermore, MYB and bHLH members, which are highly correlated (r=0.882–0.980) with anthocyanin content, modulated anthocyanin accumulation by regulating the transcription of structural genes, including CHS and F3’H, involved in the flavonoid biosynthesis pathway.ConclusionsThe present comprehensive transcriptome analyses contribute to the understanding of the the relationship between hormones and anthocyanin synthesis as well as the molecular mechanism involved in apple skin pigmentation.

Transcriptomes of Fruit Cavity Revealed by De Novo Sequence Analysis in Nai Plum (Prunus salicina)

Nai plum (Prunus salicina) is an important fruit crop in China having good taste and flavour. Cavity formation occurring during fruit development affects fruit quality. However, the molecular mechanism underlying cavity formation is unclear. To obtain differential expression profiles of cavity fruit (CF) and non-cavity fruit (nCF) in P. salicina, we sequenced the fruits at different time intervals of 7 days after anthesis (DAA), 21 and 28 DAA, respectively, and 83,869 unigenes, 3811 differentially expressed genes, 22,971 simple sequence repeats and over 14,000 single nucleotide polymorphisms were obtained. Twenty-three differentially expressed genes were selected for verification by qRT-PCR. The contents of phytohormones during fruit development showed that there was a positive relevance between phytohormone contents (IAA, ZR and GA), fruit size and ABA contents in the fruits, whereas there was a negative correlation with ZR, GA and IAA. Lower GA content in fruit before 14 DAA and higher IAA and ZR levels during later developmental stages resulted in cavity appearance. Further studies showed that differential expression of phytohormone-related genes IPT, CKX, YUCCA, GA20ox, GID1, CCS1 was determined at key fruit development stages, which is consistent with content changes of IAA, GA, ABA and ZR. Our results suggest that ABA might inhibit the synthesis of IAA, ZR and GA and cause fruit cavity formation in Nai plum.

Auxin abolishes inhibitory effects of methylcyclopropen and amino oxyacetic acid on pollen grain germination, pollen tube growth, and the synthesis of ACC in petunia

As established by us earlier, ethylene behaves as a regulator of germination, development, and growth of male gametophyte during the progamic phase of fertilization. However, the mechanisms of the regulation of these processes remain so far unstudied. It is believed that the main factor providing variety of the ethylene responses is its interaction with other phytohormones. According to our working hypothesis, ethylene controls germination of pollen grains (PGs) and growth of pollen tubes (PTs) by interacting with auxin, which, as the available data indicate, is likely a key regulator of plant cell polarization and morphogenesis and one of the factors modulating the biosynthesis of ethylene at the level of ACC-synthase gene expression. In the present work, on germinating in vitro male gametophyte and the pollen-stigma system for petunia (Petunia hybrida L.) effects of phytohormones (ethylene and IAA) and known blockers repressing ethylene reception (1-methylcyclopropene, 1-MCP), the synthesis of ACC (amino oxyacetic acid, AOA) and transport IAA (triyodbenzoynaya acid, TYBA) on PGs germination, PTs growth and the synthesis of ACC were investigated. According to the data obtained, exogenous ethylene and IAA stimulated both PGs germination and PTs growth. 1-MCP and TYBA completely inhibited the first process, whereas IAA abolished the inhibitory action of 1-MCP and AOA on both the above processes. Etrel only partially weakened the inhibitory effect of TYBA. Examination of ACC synthesis modulation with AOA showed that IAA does not affect the level of ACC in germinating in vitro male gametophyte and nonpollinated stigmas, while this phytohormone insignificantly raised the level of ACC and abolished the inhibitory effect of AOA on its synthesis in the pollenstigma system. Pollination of stigmas with the pollen preliminarily treated with 1-MCP led to 2.5-fold decline in both the rate of PT growth and the level of ACC. At the same time, IAA abolished the inhibitory action of 1-MCP recovering the synthesis of ACC and growth of PTs to the control values. All these results, taken together, provide evidence for the interaction of the signal transduction pathways of ethylene and auxin at the level of ACC biosynthesis in the course of germination and growth of petunia male gametophyte during the progamic phase of fertilization.

Balance between salt stress and endogenous hormones influence dry matter accumulation in Jerusalem artichoke

Salinity is one of the most serious environmental stresses limiting agricultural production. Production of Jerusalem artichoke on saline land is strategically important for using saline land resources. The interaction between plant hormones and salinity stress in governing Jerusalem artichoke (Helianthus tuberosus) growth is unclear. Jerusalem artichoke (variety Nanyu-1) was grown under variable salinity stress in the field, and a role of endogenous hormones [zeatin (ZT), auxins (IAA), gibberellins (GA3) and abscisic acid (ABA)] in regulating sugar and dry matter accumulation in tubers was characterized. Under mild salt stress (≤2.2gNaClkg−1 soil), Nanyu-1 grew well with no significant alteration of dry matter distribution to stems and tubers. In contrast, under moderate salt stress (2.7gNaClkg−1 soil), the distribution to stem decreased and to tubers decreased significantly. Mild salt stress induced sugar accumulation in tubers at the beginning of the tuber-expansion period, but significantly inhibited (i) transfer of non-reducing sugars to tubers, and (ii) polymerization and accumulation of fructan during the tuber-expansion stage. Under different salinity stress, before the stolon growth, the ratio of IAA/ABA in leaves increased significantly and that of GA3/ABA increased slightly; during tuber development, these ratios continued to decrease and reached the minimum late in the tuber-expansion period. While, salt stress inhibited (i) underground dry matter accumulation, (ii) tuber dry matter accumulation efficiency, (iii) transport of non-reducing sugars to tubers, and (iv) fructan accumulation efficiency during the tuber-expansion period; these effects were accompanied by significantly decreased tuber yield with an increase in salinity. With soil salinity increasing, the synthesis of IAA and GA3 was inhibited in leaves and tubers, while ABA synthesis was stimulated. In brief, tuber yield would significantly decreased with the increase of salinity.

Suppression of charcoal rot in soybean by moderately halotolerant Pseudomonas aeruginosa GS-33 under saline conditions.

Charcoal rot severely limits the soybean crop yield under saline conditions. The present studies focus on biocontrol and plant growth promoting potential of phenazine producing moderately halotolerant Pseudomonas aeruginosa (GS-33) in soybean under saline soil conditions. A marine isolate; GS-33 was identified as P. aeruginosa based on polyphasic characterization. This strain showed potent in vitro biocontrol activity against charcoal rot causing fungus Macrophomina phaseolina. It was capable of producing phenazine-1-carboxylic acid even at elevated salt concentrations. Moreover, GS-33 possessed other biocontrol traits like production of siderophores, HCN and protease under saline conditions. Multiple traits for plant growth promotion such as synthesis of IAA, NH3 , and solubilization of phosphate were also exhibited by GS-33. Plant growth promoting and biocontrol control potentials of GS-33 were evaluated by pot assay under saline soil conditions. Higher biomass and chlorophyll content were observed in GS-33 treated seedlings. A greater reduction in charcoal rot caused by fungal pathogens under both normal and saline soil conditions in GS-33 treated seedlings was observed. In a nut shell, phenazine producing halotolerant strain GS-33 could mitigate saline soil conditions (abiotic stress) and infestation of M. phaseolina (biotic stress) in soybean.

Growth responses to sulfate and chloride are related to different phytohormone profiles in the halophyte Prosopis strombulifera

In this study, the profile of plant phytohormones traditionally considered as plant growth promoters (GA1, GA3, GA4, IAA and Z) was determined in roots and leaves of the halophyte Prosopis strombulifera grown hydroponically in iso-osmotic solutions of NaCl, Na2SO4 and their mixture. Hormonal levels were correlated with growth parameters and ABA levels. Different sodium salts in the medium differentially affected the synthesis of these compounds. NaCl treated plants showed the greatest accumulation of GA4 and GA1 and lower levels of their metabolites GA8 and GA34 both in root and leaves, in coincidence with the optimum growth observed at ?o -1.9 Mpa this response was also observed at ?o -2.6 MPa. IAA level was unaltered in these plants while Z content was higher in roots than in leaves. In contrast, both leaves and roots from Na2SO4 treated plants showed lower GA1 and GA4 and increased GA8 and GA34 levels at high salinity. High levels of IAA were found in roots of these plants, but the ABA/IAA ratio increased with increasing salt concentrations in the culture medium. This pattern was also observed in the high ABA/GAs ratios. Z levels were very low in all salt treatments. The results of this study show that the halophytic growth under NaCl treatment is mainly regulated by GA1 and GA4 and low relative levels of ABA and IAA. The toxicity of sulfate alters this pattern reversing the ratio ABA/GAs and increasing the synthesis of IAA in conjunction with increased lateral root formation. In bisaline-treated plants intermediate values were observed in the levels of these phytohormones as compared to monosaline treatment.

Trichome expression of iaaM transgene influences their development and elongation in tobacco

The iaaM gene encodes a monooxygenase, an enzyme that can catalyze the synthesis of IAA from tryptophan and is functional in plants. We cloned the iaaM into the T-DNA region of a Ti binary vector pWM101 under the control of the cotton fiber specific E6 promoter, and the recombinant was transformed into Nicotiana tabacum WS38 via leaf disc infection with Agrobacterium tumefaciencs GV3101 that harbored the Ti plasmid. Some 25 transformed seedlings were screened out, and the trichomes of the transgenic leaves were both denser and lengthier. The E6 promoter-specific expression of iaaM in trichomes led to the more active auxin synthesis in the cells and allowed the transgenic leaves to develop tidier and longer trichomes. As more trichomes developed on the transgenic leaves, the leaf epidermis appeared fuzzier than the wild control. The research showed that iaaM expression in trichomes influenced the development of trichomes both during their initiation and elongation.

Studies on nitrogen fixing bacteria and their application on the growth of seedling of Ocimum sanctum

IntroductionRepresentatives of the Azotobacteriaceae family are regular inhabitants of soils of roots (rhizosphere) and on the root surface of free-living nitrogen fixing bacteria of the genera Azotobacter and Azospirillum. They are the regular associates of the roots of many tropical grasses and cereals. Their associations with medicinal plants are of paramount importance. The medicinal plants such as Aloe vera and Datura alba were selected to access the nature of association in the rhizosphere and on the roots by the above bacteria. MethodsThe roots of A. vera had the dominance of nitrogen fixing bacteria (132 × l02/g). The characteristics of the selected bacteria revealed the presence of Azotobacter chroococcum, Azotobacter beijerinckii, Azotobacter vinelandii and Azospirillum lipoferum. The carbon sources such as sucrose, lactose, glucose, maltose, rhamnose, xylose and mannitol either individually or in combination induced the growth of selected nitrogen fixing bacteria (A. chroococcum, A. beijerinckii, and A. vinelandii). ResultsThe maximum growth was recovered with maltose and glucose (1.36S0.D). The mixed carbon sources such as mannitol, maltose and xylose showed elevated growth of the bacterium (A. chroococcum and A. beijerinckii). The production of IAA, a growth promoting hormone by A. chroococcum, A. beijerinckii and A. vinelandii was studied at varying pH ranges from 6 to 9 in the growing medium. The increase in the pH stimulated the growth as well as the synthesis of IAA. Both the growth and the growth hormones are similar in the growing liquid broth. The above observations paved the way for accessing the growth of the seedling of Ocimum sanctum. The application of Azotobacter and Azospirillum species as biofertilizers is a testimony to the effect that IAA on seedlings growth. ConclusionWith this we conclude that IAA with its growth promoting capacity dominates the Microbial and Agricultural Biotechnology in the years to come.