IAA Biosynthesis Research Articles

Identification and characterization of miRNAs and PHAS loci related to the early development of the embryo and endosperm in Fragaria × ananassa

BackgroundThe strawberry fleshy fruit is actually enlarged receptacle tissue, and the successful development of the embryo and endosperm is essential for receptacle fruit set. MicroRNAs (miRNAs) and phased small interfering RNAs (phasiRNAs) play indispensable regulatory roles in plant growth and development. However, miRNAs and phasiRNAs participating in the regulation of strawberry embryo and endosperm development have yet to be explored.ResultsHere, we performed genome-wide identification of miRNA and phasiRNA-producing loci (PHAS) in strawberry seeds with a focus on those involved in the development of the early embryo and endosperm. We found that embryos and endosperm have different levels of small RNAs. After bioinformatics analysis, the results showed that a total of 404 miRNAs (352 known and 52 novel) and 156 PHAS genes (81 21-nt and 75 24-nt genes) could be found in strawberry seed-related tissues, of which four and nine conserved miRNA families displayed conserved expression in the endosperm and embryo, respectively. Based on refined putative annotation of PHAS loci, some auxin signal-related genes, such as CM3, TAR2, AFB2, ASA1, NAC and TAS3, were found, which demonstrates that IAA biosynthesis is important for endosperm and embryo development during early fruit growth. Additionally, some auxin signal-related conserved (miR390-TAS3) and novel (miR156-ASA1) trigger-PHAS pairs were identified.ConclusionsTaken together, these results expand our understanding of sRNAs in strawberry embryo and endosperm development and provide a genomic resource for early-stage fruit development.

Ultrasound, as a hypomethylating agent, remodels DNA methylation and alters mRNA transcription in winter wheat (Triticum aestivum L.) seedlings.

Any treatment that affects seed germination and seedling development is of paramount importance from an agricultural point of view since they are critical prerequisites for successful crop production. In present study, we have examined the after-effect of ultrasonication (at 30 kHz, 70 W for 5min) of winter wheat (Triticum aestivum L. cv. SE15) seeds on the early seedling growth and development, and accompanying changes in the DNA methylation and transcriptomic pattern in 7-day-old seedlings. We used mRNA-sequencing and whole genome bisulfite sequencing (WGBS) to identify significantly differentially expressed genes (DEGs), significantly differently methylated regions (DMRs) and genes (DMGs). Ultrasonication of seeds did not alter the germination rate but increased both the length and weight of roots and shoots of 7-day-old seedlings significantly by 23%-68% and 16%-28%, respectively. Analyzing the expression intensity of 107,891 genes, significantly differentially expressed sequences related mainly to starch biosynthesis, IAA biosynthesis, photosynthesis and TCA cycle pathways. The same pathways were also affected by DNA-methylation changes. DNA hypomethylation occurred in the global methylation profile after ultrasound treatment altering the accessibility of some genes for transcription. Transcriptomic changes suggested alterations in the crosstalk between IAA and sucrose signaling, enhancement of growth processes, and increased activity of nuclear transcription factor stimulating the transcription of genes having CCAAT motif in the promoter. In the present first whole genome level study, we have identified seed ultrasonication as a priming technique that can act as a hypomethylating agent and thereby is able to modify the mRNA transcription allowing enhanced seedling growth.

Improvement of salt tolerance of Arabidopsis thaliana seedlings inoculated with endophytic Bacillus cereus KP120

ABSTRACT In our previous reports, an endophytic bacterium, Bacillus cereus KP120 was isolated from the halophyte species Kosteletzkya virginica. In this study, the effect of KP120 colonization on Arabidopsis thaliana seedlings was investigated. Our results showed that inoculation with KP120 could promote the growth of A. thaliana seedlings plants under salt-stress conditions, compared with uninoculated controls. After salt treatment, chlorophyll, proline, the activity of antioxidant enzymes, Indole-3-acetic acid and 1-aminocyclopropane-1-carboxylate-deaminase in plants inoculated were increased significantly but malondialdehyde content was decreased compared with the plants under salt stress lonely. Similarly, under non-salt stress, physiological indices above except for MDA in plants inoculated with KP120 were increased compared with control. B. cereus also induced the up-regulation of key genes involved in IAA biosynthesis, responses, transport, down-regulated expression of genes related with ethylene synthesis and response. Our work principally demonstrates that Bacillus cereus KP120 significantly enhances plant growth and increases plant tolerance to salt stress.

Plant growth-promoting effect and genomic analysis of the P. putida LWPZF isolated from C. japonicum rhizosphere

Plant growth-promoting rhizobacteria are a type of beneficial bacteria which inhabit in the rhizosphere and possess the abilities to promote plant growth. Pseudomonas putida LWPZF is a plant growth-promoting bacterium isolated from the rhizosphere soil of Cercidiphyllum japonicum. Inoculation treatment with LWPZF could significantly promote the growth of C. japonicum seedlings. P. putida LWPZF has a variety of plant growth-promoting properties, including the ability to solubilize phosphate, synthesize ACC deaminase and IAA. The P. putida LWPZF genome contained a circular chromosome (6,259,530 bp) and a circular plasmid (160,969 bp) with G+C contents of 61.75% and 58.25%, respectively. There were 5632 and 169 predicted protein-coding sequences (CDSs) on the chromosome and the plasmid respectively. Genome sequence analysis revealed lots of genes associated with biosynthesis of IAA, pyoverdine, ACC deaminase, trehalose, volatiles acetoin and 2,3-butanediol, 4-hydroxybenzoate, as well as gluconic acid contributing phosphate solubilization. Additionally, we identified many heavy metal resistance genes, including arsenate, copper, chromate, cobalt-zinc-cadmium, and mercury. These results suggest that P. putida LWPZF shows strong potential in the fields of biofertilizer, biocontrol and heavy metal contamination soil remediation. The data presented in this study will allow us to better understand the mechanisms of plant growth promotion, biocontrol, and anti-heavy metal of P. putida LWPZF.

Growth-Defense Trade-Offs Induced by Long-term Overgrazing Could Act as a Stress Memory.

Long-term overgrazing (OG) is one of the key drivers of global grassland degradation with severe loss of productivity and ecosystem functions, which may result in stress memory such as smaller stature of grassland plants. However, how the OG-induced stress memory could be regulated by phytohormones is unknown. In this study, we investigated the changes of four phytohormones of cloned offspring of Leymus chinensis that were developed from no-grazing (NG) plants and OG plants with a grazing history of 30 years. The concentrations of auxin (IAA) and gibberellic acid (GA) in OG plant leaves were 45% and 20% lower than control, respectively. Meanwhile, the level of abscisic acid (ABA) in OG leaves nearly doubled compared with that in NG leaves. The situation was quite similar in roots. Unexpectedly, no significant changes in the jasmonic acid (JA) level were observed between OG and NG plants. The changes in gene expression patterns between OG and NG plants were also investigated by transcriptomic analysis. In total, 302 differentially expressed genes (DEGs) were identified between OG and NG plants, which were mainly classified into the functions of synthesis, receptor, and signal transduction processes of phytohormones. The expression of 24 key genes related to the biosynthesis and signal transduction of IAA and GA was downregulated in OG plants. Among them, OASA1 and AO1 (regulating the biosynthesis of IAA and ABA, respectively) were reduced significantly by 88 and 92%, respectively. In addition, the content of secondary metabolites related to plant defense such as flavonoids and phenols was also increased in leaves. Taken together, the decrease of positive plant growth-related hormones (IAA and GA) together with the increase of plant stress-related hormones or factors (ABA, flavonoids, and phenols) induced the growth-defense trade-offs for L. chinensis adaptation to long-term OG stress. The findings reported in this study shed new light on the mechanism of plant–animal interaction in the grassland ecosystem and provide a deeper insight into optimizing grazing management and sustainable utilization of grassland.

Piriformospora indica colonization promotes the root growth of Dimocarpus longan seedlings

As a mutualistic endophyte, the host range of Piriformospora indica is very broad and its promoting effects on host plant growth and development have been increasingly reported. In this study, we investigated the influence of P. indica colonization on the growth of longan (Dimocarpus longan Lour.) seedlings and found that the root length and root number, chlorophyll content in leaf, and flavonoid contents in both leaf and stem of P. indica colonized longan seedlings were significantly higher than those of the noncolonized controls. To reveal its promoting mechanism, activities of several antioxidant enzymes, contents of some antioxidant related molecules and phytohormones were measured. Results showed that the peroxidase (POD) activity (indicator of rooting ability) and indole-3-acetic acid (IAA, a root growth promoting phytohormone) content in P. indica colonized roots were both significantly higher than controls. Moreover, P. indica colonization reduced the accumulations of hydrogen peroxide (H2O2), malondialdehyde (MDA) and jasmonic acid (JA) in longan roots. Our results indicated that P. indica colonization improved the rooting ability of longan through inducing the IAA biosynthesis and POD activity, facilitated and accelerated the root growth by reducing H2O2 accumulation and suppressing the JA accumulation.

Function Analysis of the ERF and DREB Subfamilies in Tomato Fruit Development and Ripening.

APETALA2/ethylene responsive factors (AP2/ERF) are unique regulators in the plant kingdom and are involved in the whole life activity processes such as development, ripening, and biotic and abiotic stresses. In tomato (Solanum lycopersicum), there are 140 AP2/ERF genes; however, their functionality remains poorly understood. In this work, the 14th and 19th amino acid differences in the AP2 domain were used to distinguish DREB and ERF subfamily members. Even when the AP2 domain of 68 ERF proteins from 20 plant species and motifs in tomato DREB and ERF proteins were compared, the binding ability of DREB and ERF proteins with DRE/CRT and/or GCC boxes remained unknown. During fruit development and ripening, the expressions of 13 DREB and 19 ERF subfamily genes showed some regular changes, and the promoters of most genes had ARF, DRE/CRT, and/or GCC boxes. This suggests that these genes directly or indirectly respond to IAA and/or ethylene (ET) signals during fruit development and ripening. Moreover, some of these may feedback regulate IAA or ET biosynthesis. In addition, 16 EAR motif-containing ERF genes in tomato were expressed in many organs and their total transcripts per million (TPM) values exceeded those of other ERF genes in most organs. To determine whether the EAR motif in EAR motif-containing ERF proteins has repression function, their EAR motifs were retained or deleted in a yeast one-hybrid (YIH) assay. The results indicate that most of EAR motif-containing ERF proteins lost repression activity after deleting the EAR motif. Moreover, some of these were expressed during ripening. Thus, these EAR motif-containing ERF proteins play vital roles in balancing the regulatory functions of other ERF proteins by completing the DRE/CRT and/or GCC box sites of target genes to ensure normal growth and development in tomato.

A Salt-Tolerant Streptomyces paradoxus D2-8 from Rhizosphere Soil of Phragmites communis Augments Soybean Tolerance to Soda Saline-Alkali Stress.

Soil salinity and alkalization limit plant growth and agricultural productivity worldwide. The application of salt-tolerant plant growth-promoting rhizobacteria (PGPR) effectively improved plant tolerance to saline-alkali stress. To obtain the beneficial actinomyces resources with salt tolerance, thirteen isolates were isolated from rhizosphere saline and alkaline soil of Phragmites communis. Among these isolates, D2-8 was moderately halophilic to NaCl and showed 120 mmol soda saline-alkali solution tolerance. Moreover, the plant growth-promoting test demonstrated that D2-8 produced siderophore, IAA, 1-aminocyclopropane-1-carboxylate deaminase (ACCD), and organic acids. D2-8 showed 99.4% homology with the type strain Streptomyces paradoxus NBRC 14887T and shared the same branch, and, therefore, it was designated S. paradoxus D2-8. Its genome was sequenced to gain insight into the mechanism of growth-promoting and saline-alkali tolerance of D2-8. IAA and siderophore biosynthesis pathway, genes encoding ACC deaminase, together with six antibiotics biosynthesis gene clusters with antifungal or antibacterial activity, were identified. The compatible solute ectoine biosynthesis gene cluster, production, and uptake of choline and glycine betaine cluster in the D2-8 genome may contribute to the saline-alkali tolerance of the strain. Furthermore, D2-8 significantly promoted the seedling growth even under soda saline-alkali stress, and seed coating with D2-8 isolate increased by 5.88% of the soybean yield in the field. These results imply its significant potential to improve soybean soda saline-alkali tolerance and promote crop health in alkaline soil.

Identification and Characterization of Auxin/IAA Biosynthesis Pathway in the Rice Blast Fungus Magnaporthe oryzae.

The rice blast fungus Magnaporthe oryzae has been known to produce the phytohormone auxin/IAA from its hyphae and conidia, but the detailed biological function and biosynthesis pathway is largely unknown. By sequence homology, we identified a complete indole-3-pyruvic acid (IPA)-based IAA biosynthesis pathway in M. oryzae, consisting of the tryptophan aminotransferase (MoTam1) and the indole-3-pyruvate decarboxylase (MoIpd1). In comparison to the wild type, IAA production was significantly reduced in the motam1Δ mutant, and further reduced in the moipd1Δ mutant. Correspondingly, mycelial growth, conidiation, and pathogenicity were defective in the motam1Δ and the moipd1Δ mutants to various degrees. Targeted metabolomics analysis further confirmed the presence of a functional IPA pathway, catalyzed by MoIpd1, which contributes to IAA/auxin production in M. oryzae. Furthermore, the well-established IAA biosynthesis inhibitor, yucasin, suppressed mycelial growth, conidiation, and pathogenicity in M. oryzae. Overall, this study identified an IPA-dependent IAA synthesis pathway crucial for M. oryzae mycelial growth and pathogenic development.

Effects of root restriction on phytohormone levels in different growth stages and grapevine organs

Phytohormones play important roles in germination, blossom, senescence, abscission of plants by a series of signal transduction and molecular regulation. The purpose of this research was to investigate the influence of root restriction (RR) cultivation on plant endogenous hormone variation tendency at different growth stages in diverse organs or tissues. ‘Muscat Hamburg’ (Vitis ‘Muscat of Alexandria’ × Vitis ‘Trollinger’) grapevine was used as test material. High Performance Liquid Chromatography (HPLC) was used to quantify hormone levels, qRT-PCR was used to quantify the expression of genes related to hormone biosynthesis pathway, and determined parameters of growth and photosynthetic, aiming to investigate the influence of root restriction on the formation and metabolism of phytohormones, as well as the degree of correlation between phytohormones and plant growth and photosynthetic intensity under root restriction. By measuring the photosynthetic rate of leaves at the stages of core-hardening, veraison and maturity, it was found that root restriction could reduce most photosynthetic parameters. The results also revealed that RR treatment increased abscisic acid (ABA), salicylic acid (SA), zeatin riboside (ZR), N6-(delta 2-isopentenyl)-adenine nucleoside (iPR) concentrations, while reduced auxin (IAA), 3-indolepropionic acid (IPA), 3-indolebutyric acid (IBA), gibberellin A3 (GA3), zeatin (ZT), N6-(delta 2-Isopentenyl)-adenine (iP), kinetin (KT), jasmonic acid (JA) and methyl jasmonate (MeJA) concentrations in most organs and at most developmental stages. RT-qPCR was carried out to further explore the effect of root restriction on genes expression of ABA, SA and IAA biosynthesis pathways at molecular level. Meanwhile, through correlation analysis, we found that different phytohormones contributed differently to physiological indicators, there existed strong correlation of ABA, KT, MeJA, iPR, SA, JA with leaf photosynthesis, GA3, IBA, ZR, IAA, ZT with fruit quality. In addition, we also found that the shoot growth related parameters were closely correlated with JA, IPA and iP. To sum up, our results suggested that RR treatment could significantly increase soluble solid content, regulate the growth and photosynthesis of grapevine, by affecting the biosynthesis of phytohormones. It could further prove that root restriction was a feasible technique to ameliorate the phenomenon of low quality in grape berry in southern China.

The Ethylene Biosynthesis Gene CpACO1A: A New Player in the Regulation of Sex Determination and Female Flower Development in Cucurbita pepo.

A methanesulfonate-generated mutant has been identified in Cucurbita pepo that alters sex determination. The mutation converts female into hermaphrodite flowers and disrupts the growth rate and maturation of petals and carpels, delaying female flower opening, and promoting the growth rate of ovaries and the parthenocarpic development of the fruit. Whole-genome resequencing allowed identification of the causal mutation of the phenotypes as a missense mutation in the coding region of CpACO1A, which encodes for a type I ACO enzyme that shares a high identity with Cucumis sativus CsACO3 and Cucumis melo CmACO1. The so-called aco1a reduced ACO1 activity and ethylene production in the different organs where the gene is expressed, and reduced ethylene sensitivity in flowers. Other sex-determining genes, such as CpACO2B, CpACS11A, and CpACS27A, were differentially expressed in the mutant, indicating that ethylene provided by CpACO1A but also the transcriptional regulation of CpACO1A, CpACO2B, CpACS11A, and CpACS27A are responsible for determining the fate of the floral meristem toward a female flower, promoting the development of carpels and arresting the development of stamens. The positive regulation of ethylene on petal maturation and flower opening can be mediated by inducing the biosynthesis of JA, while its negative control on ovary growth and fruit set could be mediated by its repressive effect on IAA biosynthesis.

Autocatalytic biosynthesis of abscisic acid and its synergistic action with auxin to regulate strawberry fruit ripening.

Abscisic acid (ABA) plays a major role in the regulation of strawberry fruit ripening; however, the origin of the ABA signal is largely unknown. Here, we report an autocatalytic mechanism for ABA biosynthesis and its synergistic interaction with auxin to regulate strawberry fruit ripening. We demonstrate that ABA biosynthesis is self-induced in the achenes but not in the receptacle, resulting in its substantial accumulation during ripening. ABA was found to regulate both IAA transport and biosynthesis, thereby modulating IAA content during both early fruit growth and later fruit ripening. Taken together, these results reveal the origins of the ABA signal and demonstrate the importance of its coordinated action with IAA in the regulation of strawberry fruit development and ripening.

Rhizophere analysis of auxin producers harboring the phenylpyruvate decarboxylase pathway

The 3-indole acetic acid (IAA) produced by microorganisms in the rhizosphere modulates root growth and physiology, but the analysis of these microorganisms relies on the isolation of culturable IAA producers as molecular tools are lacking. Microbial biosynthesis of IAA may involve several pathways, like the phenylpyruvate decarboxylase pathway (using the ppdC gene) present in many phytobeneficial microorganisms. Here, we tested the hypothesis that PCR primers could be developed to quantify ppdC+ microorganisms and assess ppdC allele diversity in the rhizosphere and bulk soil. Effective ppdC primers were obtained and validated in silico and using individual ppdC+ strains. By qPCR, they enabled to evidence high abundance of ppdC+ microorganisms in different types of bulk and rhizospheric soils, up to 8 log of ppdC copies per g of soil. OTUs obtained with Illumina sequencing of bulk and rhizospheric soil samples clustered in numerous clades encompassing almost all the known ppdC diversity in soil environments, and pointing to soil type and plant species as factors potentially shaping ppdC allelic diversity. In conclusion, these new primers enabled the first culture-independent analysis of the ppdC+ functional group of IAA producers in environmental samples.

Spatiotemporal auxin distribution in Arabidopsis tissues is regulated by anabolic and catabolic reactions under long-term ammonium stress

BackgroundThe plant hormone auxin is a major coordinator of plant growth and development in response to diverse environmental signals, including nutritional conditions. Sole ammonium (NH4+) nutrition is one of the unique growth-suppressing conditions for plants. Therefore, the quest to understand NH4+-mediated developmental defects led us to analyze auxin metabolism.ResultsIndole-3-acetic acid (IAA), the most predominant natural auxin, accumulates in the leaves and roots of mature Arabidopsis thaliana plants grown on NH4+, but not in the root tips. We found changes at the expressional level in reactions leading to IAA biosynthesis and deactivation in different tissues. Finally, NH4+ nutrition would facilitate the formation of inactive oxidized IAA as the final product.ConclusionsNH4+-mediated accelerated auxin turnover rates implicate transient and local IAA peaks. A noticeable auxin pattern in tissues correlates with the developmental adaptations of the short and highly branched root system of NH4+-grown plants. Therefore, the spatiotemporal distribution of auxin might be a root-shaping signal specific to adjust to NH4+-stress conditions.

Plant Hormone Metabolome and Transcriptome Analysis of Dwarf and Wild-type Banana

Gibberellin (GA), auxin (IAA) and brassinosteroid (BR) are indispensable in the process of plant growth and development. Currently, research on the regulatory mechanism of phytohormones in banana dwarfism is mainly focused on GA, and few studies are focused on IAA and BR. In this study, we measured the contents of endogenous GA, IAA and BR and compared the transcriptomes of wild-type Williams banana and its dwarf mutant across five successive growth periods. We investigated the relationship between hormones and banana dwarfism and explored differential gene expression through transcriptome analysis, thus revealing the possible metabolic regulatory mechanism. We inferred a complex regulatory network of banana dwarfing. In terms of endogenous hormone levels, GA and IAA had significant effects on banana dwarfing, while BR had little effect. The key gene in GA biosynthesis of is GA2ox, and the key genes in IAA biosynthesis are TDC and YUCCA. The differential expression of these genes might be the main factor affecting hormone levels and plant height. In terms of hormone signal transduction, DELLA and AUX/IAA repressor proteins were the core regulators of GA and IAA, respectively. They inhibited the process of signal transduction and had feedback regulation on hormone levels. Finally, the transporter protein PIN, AUX1/LAX protein family and ABCB subfamily played supplementary roles in the transport of IAA. These results provide new insights into GA and IAA regulation of banana growth and a reliable foundation for the improvement of dwarf varieties.

Glycolate oxidase-dependent H2O2 production regulates IAA biosynthesis in rice

BackgroundGlycolate oxidase (GLO) is not only a key enzyme in photorespiration but also a major engine for H2O2 production in plants. Catalase (CAT)-dependent H2O2 decomposition has been previously reported to be involved in the regulation of IAA biosynthesis. However, it is still not known which mechanism contributed to the H2O2 production in IAA regulation.ResultsIn this study, we found that in glo mutants of rice, as H2O2 levels decreased IAA contents significantly increased, whereas high CO2 abolished the difference in H2O2 and IAA contents between glo mutants and WT. Further analyses showed that tryptophan (Trp, the precursor for IAA biosynthesis in the Trp-dependent biosynthetic pathway) also accumulated due to increased tryptophan synthetase β (TSB) activity. Moreover, expression of the genes involved in Trp-dependent IAA biosynthesis and IBA to IAA conversion were correspondingly up-regulated, further implicating that both pathways contribute to IAA biosynthesis as mediated by the GLO-dependent production of H2O2.ConclusionWe investigated the function of GLO in IAA signaling in different levels from transcription, enzyme activities to metabolic levels. The results suggest that GLO-dependent H2O2 signaling, essentially via photorespiration, confers regulation over IAA biosynthesis in rice plants.

Silicon induces adventitious root formation in rice under arsenate stress with involvement of nitric oxide and indole-3-acetic acid.

Arsenic (As) negatively affects plant development. This study evaluates how the application of silicon (Si) can favor the formation of adventitious roots in rice under arsenate stress (AsV) as a mechanism to mitigate its negative effects. The simultaneous application of AsV and Si up-regulated the expression of genes involved in nitric oxide (NO) metabolism, cell cycle progression, auxin (IAA, indole-3-acetic acid) biosynthesis and transport, and Si uptake which accompanied adventitious root formation. Furthermore, Si triggered the expression and activity of enzymes involved in ascorbate recycling. Treatment with L-NAME (NG-nitro L-arginine methyl ester), an inhibitor of NO generation, significantly suppressed adventitious root formation, even in the presence of Si; however, supplying NO in the growth media rescued its effects. Our data suggest that both NO and IAA are essential for Si-mediated adventitious root formation under AsV stress. Interestingly, TIBA (2,3,5-triiodobenzoic acid), a polar auxin transport inhibitor, suppressed adventitious root formation even in the presence of Si and SNP (sodium nitroprusside, an NO donor), suggesting that Si is involved in a mechanism whereby a cellular signal is triggered and that first requires NO formation, followed by IAA biosynthesis.

Different pH levels medium effects in IAA production of phylloplane bacterium Serratia plymuthica strain UBCF_13

Indole-3-acetic acid [IAA] is the main source of auxin in plants that plays a major role in controlling various physiological processes. The ability of bacterium in IAA biosynthesis depends on several environmental factors, usually triggered by acidic stresses. This study was aimed to optimize the IAA production by phylloplane bacterium Serratiaplymuthica strain UBCF_13 with various pH levels. Optimization was carried out by using 0.2% L-Tryptophan in Luria Bertani[LB] media with various pH levels namely pH 4.0; 4.5; 5.0; 5.5; 6.0; 6.5; 7.0 and 9.0. UBCF_13 showed the best IAA production at pH 6.0 and 0.2% L-Tryptophan exhibited IAA concentration in the amount of 24.13 ppm. The UBCF_13 extracellular protein profile analysis showed that at pH 6.0 induced L-Tryptophan 0.2% produced protein bands of 60.8 kDa and 45 kDa in size. These protein bands are assumed to be ipdC and nitrilase proteins which are involved in the IAA biosynthesis. The application of IAA was carried out using chili peppers [Capsicum annuum L.] germination of the Lotanbar genotype. The application was using supernatant produced from media of pH 6.0 and 0.2% L-Tryptophan. The results show that root and hypocotyl lengths were 4.10 cm and 2.90 cm, respectively. Meanwhile, root and hypocotyl lengths in the control sample only 2.78 cm and 1.88 cm. The results indicated that the IAA production of UBCF_13 can promote the growth of chili seedling. A further detailed study on the visualization of protein profiles at the optimum treatment needs to be done. Two-DimensionalElectrophoresis is recommended to be applied so that protein bands can be accurately separated to identify detailed proteins involved in the IAA biosynthesis.

Planting Density Affects Panax notoginseng Growth and Ginsenoside Accumulation by Balancing Primary and Secondary Metabolism.

Adjusting planting density is a common agricultural practice used to achieve maximum yields. However, whether the quality of medicinal herbs can be improved by implementing appropriate planting densities is still uncertain. The medicinal crop Panax notoginseng was used to analyze the effects of planting density on growth and ginsenoside accumulation, and the possible mechanisms of these effects were revealed through metabonomics. The results showed that P. notoginseng achieved high ginsenoside accumulation at high planting densities (8 × 8 and 10 × 10 cm), while simultaneously achieved high biomass and ginsenoside accumulation at moderate planting density of 15 × 15 cm. At the moderate planting density, the primary metabolism (starch and sucrose metabolism) and secondary metabolism (the biosynthesis of phytohormone IAA and ginsenoside) of the plants were significantly enhanced. However, the strong intraspecific competition at the high planting densities resulted in stress as well as the accumulation of phytohormones (SA and JA), antioxidants (gentiobiose, oxalic acid, dehydroascorbic acid) and other stress resistance-related metabolites. Interestingly, the dry biomass and ginsenoside content were significantly lower at low densities (20 × 20 and 30 × 30 cm) with low intraspecific competition, which disturbed normal carbohydrate metabolism by upregulating galactose metabolism. In summary, an appropriate planting density was benefit for the growth and accumulation of ginsenosides in P. notoginseng by balancing primary metabolism and secondary metabolism.

Promotion of tomato growth by the volatiles produced by the hypovirulent strain QT5-19 of the plant gray mold fungus Botrytis cinerea

Our previous study identified a hypovirulent strain QT5-19 of Botrytis cinerea, the causal agent of the plant gray mold disease, and found that QT5-19 can produce volatile organic compounds (VOCs) with high antifungal activity and high control efficacy against B. cinerea. However, impact of the QT5-19 VOCs on plant growth remains unknown. This study was conducted to investigate the impact of the QT5-19 VOCs on tomato growth, and to elucidate the mechanisms for the plant growth-promoting (PGP) activity of the QT5-19 VOCs. Results showed that compared to the control treatment, the QT5-19 VOCs significantly (P < 0.05) promoted tomato growth, and the PGP activity of the QT5-19 VOCs acted in dose- and time-dependent manners. Results also showed that the values of photosynthetic assimilation, stomatal conductance and transpiration, water use efficiency and chlorophyll content in the treatments of the QT5-19 VOCs were significantly (P < 0.05) higher than the corresponding values in the control treatment. The QT5-19 VOCs up-regulated expression of the genes for expansins (EXP2, EXP9 and EXP18), IAA (SlIAA1, SlIAA3 and SlIAA9), cytokinins (SlCKX1) and gibberellins in leaves and/or roots, whereas down-regulated expression of the gene ACO1 for ethylene in both organs. Moreover, enhanced accumulation of auxins and decreased accumulation of ethylene were observed in tomato roots in the treatment of the QT5-19 VOCs, compared to the control treatment. These results suggest that the QT5-19 VOCs probably promote tomato growth through improving photosynthesis and biosynthesis of expansins and IAA, and reducing ethylene biosynthesis. This study suggests that QT5-19 is a versatile biocontrol control agent.