Explore the vast range of titles available.

In contrast to climacteric fruits, where ethylene is known to be pivotal, the regulation of ripening in non-climacteric fruits is not well understood. In the non-climacteric strawberry (Fragaria anannassa), auxin and abscisic acid (ABA) are thought to be important, but the roles of other hormones suggested to be involved in fruit development and ripening are not clear. Here changes in the levels of indole-3-acetic acid (IAA), ABA, GA1, and castasterone from anthesis to fully ripened fruit are reported. The levels of IAA and GA1 rise early in fruit development before dropping to low levels prior to colour accumulation. Castasterone levels are highest at anthesis and drop to very low levels well before ripening commences, suggesting that brassinosteroids do not play an important role in ripening in strawberry. ABA levels are low at anthesis and gradually rise through development and ripening. The synthetic auxin, 1-naphthaleneacetic acid (NAA), can delay ripening, but the application of GA3, the gibberellin biosythesis inhibitor paclobutrazol, and ABA had no significant effect. IAA and ABA levels are higher in the developing achenes than in the receptacle tissue and may be important for receptacle enlargement and ripening, and seed maturation, respectively. Contrary to a recent report, the biologically active GA4 was not detected. The pattern of changes in the levels of the hormones are different from those reported in another well studied non-climateric fruit, grape, suggesting that a single consistent pattern of hormone changes does not occur in this group of fruit during ripening.

Arbuscular mycorrhizal symbiosis is a mutualistic interaction between most land plants and fungi of the glomeromycotina subphylum. The initiation, development and regulation of this symbiosis involve numerous signalling events between and within the symbiotic partners. Among other signals, phytohormones are known to play important roles at various stages of the interaction. During presymbiotic steps, plant roots exude strigolactones which stimulate fungal spore germination and hyphal branching, and promote the initiation of symbiosis. At later stages, different plant hormone classes can act as positive or negative regulators of the interaction. Although the fungus is known to reciprocally emit regulatory signals, its potential contribution to the phytohormonal pool has received little attention, and has so far only been addressed by indirect assays. In this study, using mass spectrometry, we analyzed phytohormones released into the medium by germinated spores of the arbuscular mycorrhizal fungus Rhizophagus irregularis. We detected the presence of a cytokinin (isopentenyl adenosine) and an auxin (indole-acetic acid). In addition, we identified a gibberellin (gibberellin A4) in spore extracts. We also used gas chromatography to show that R. irregularis produces ethylene from methionine and the α-keto γ-methylthio butyric acid pathway. These results highlight the possibility for AM fungi to use phytohormones to interact with their host plants, or to regulate their own development.

Plant growth promoting rhizobacteria (PGPR) are diverse, naturally occurring bacteria that establish a close association with plant roots and promote the growth and immunity of plants. Established mechanisms involved in PGPR-mediated plant growth promotion include regulation of phytohormones, improved nutrient availability, and antagonistic effects on plant pathogens. In this study, we isolated a bacterium from the rhizospheric soil of a soybean field in Chungcheong buk-do, South Korea. Using 16S rRNA sequencing, the bacterium was identified as Bacillus aryabhattai strain SRB02. Here we show that this strain significantly promotes the growth of soybean. Gas chromatography-mass spectrometry analysis showed that SRB02 produced significant amounts of abscisic acid, indole acetic acid, cytokinin and different gibberellic acids in culture. SRB02-treated soybean plants showed significantly better heat stress tolerance than did untreated plants. These plants also produced consistent levels of ABA under heat stress and exhibited ABA-mediated stomatal closure. High levels of IAA, JA, GA12, GA4, and GA7, were recorded in SRB02-treated plants. These plants produced longer roots and shoots than those of control plants. B. aryabhattai SRB02 was found to be highly tolerant to oxidative stress induced by H2O2 and MV potentiated by high catalase (CAT) and superoxide dismutase (SOD) activities. SRB02 also tolerated high nitrosative stress induced by the nitric oxide donors GSNO and CysNO. Because of these attributes, B. aryabhattai SRB02 may prove to be a valuable resource for incorporation in biofertilizers and other soil amendments that seek to improve crop productivity.

Indole-3-acetic acid (IAA) is an imperative phytohormone for plant growth and development. Ectomycorrhizal fungi (ECM) are able to produce IAA. However, only a few studies on IAA biosynthesis pathways in ECM fungi have been reported. This study aimed to investigate the IAA biosynthesis pathway of six ECM cultures including Astraeus odoratus, Gyrodon suthepensis, Phlebopus portentosus, Pisolithus albus, Pisolithus orientalis and Scleroderma suthepense. The results showed that all ECM fungi produced IAA in liquid medium that had been supplemented with L-tryptophan. Notably, fungal IAA levels vary for different fungal species. The detection of indole-3-lactic acid and indole-3-ethanol in the crude culture extracts of all ECM fungi indicated an enzymatic reduction of indole-3-pyruvic acid and indole-3-acetaldehyde, respectively in the IAA biosynthesis via the indole-3-pyruvic acid pathway. Moreover, the tryptophan aminotransferase activity confirmed that all ECM fungi synthesize IAA through the indole-3-pyruvic acid pathway. Additionally, the elongation of rice and oat coleoptiles was stimulated by crude culture extract. This is the first report of the biosynthesis pathway of IAA in the tested ECM fungi.

One of the most important regulatory small molecules in plants is indole-3-acetic acid, also known as auxin. Its dynamic redistribution has an essential role in almost every aspect of plant life, ranging from cell shape and division to organogenesis and responses to light and gravity 1 , 2 . So far, it has not been possible to directly determine the spatial and temporal distribution of auxin at a cellular resolution. Instead it is inferred from the visualization of irreversible processes that involve the endogenous auxin-response machinery 3 – 7 ; however, such a system cannot detect transient changes. Here we report a genetically encoded biosensor for the quantitative in vivo visualization of auxin distribution. The sensor is based on the Escherichia coli tryptophan repressor 8 , the binding pocket of which is engineered to be specific to auxin. Coupling of the auxin-binding moiety with selected fluorescent proteins enables the use of a fluorescence resonance energy transfer signal as a readout. Unlike previous systems, this sensor enables direct monitoring of the rapid uptake and clearance of auxin by individual cells and within cell compartments in planta. By responding to the graded spatial distribution along the root axis and its perturbation by transport inhibitors—as well as the rapid and reversible redistribution of endogenous auxin in response to changes in gravity vectors—our sensor enables real-time monitoring of auxin concentrations at a (sub)cellular resolution and their spatial and temporal changes during the lifespan of a plant. A genetically encoded sensor for the quantitative visualization of auxin distribution in plants enables real-time monitoring of its uptake and clearance by individual cells and within cellular compartments.

Low temperature is one of the important limiting factors for growing season and geographical distribution of plants. Zoysiagrass (Zoysia Willd) is one of the widely used warm-season turfgrass that is distribute in many parts of the world. Zoysaigrass native to high latitude may have evolved higher cold tolerance than the ones native to low latitude. The objective of this study was to investigate the cold stress response in zoysiagrass native to diverse latitude at phenotypic, physiological and metabolic levels. Two zoysiagrass (Z. japonica) genotypes, Latitude-40 (higher latitude) and Latitude-22 (lower latitude) were subjected to four temperature treatments (optimum, 30/25°C, day/night; suboptimum, 18/12°C; chilling, 8/2°C; freezing, 2/-4°C) progressively in growth chambers. Low temperature (chilling and freezing) increased leaf electrolyte leakage (EL) and reduced plant growth, turf quality, chlorophyll (Chl) content, photochemical efficiency (Fv/Fm) and photosynthesis (Pn, net photosynthetic rate; gs, stomatal conductance; intercellular CO2; Tr, transpiration rate) in two genotypes, with more rapid changes in Latitude-22. Leaf carbohydrates content (glucose, fructose, sucrose, trehalose, fructan, starch) increased with the decreasing of temperature, to a great extend in Latitude-40. Leaf abscisic acid (ABA), salicylic acid (SA) and jasmonic acid (JA) content increased, while indole-3-acetic acid (IAA), gibberellic acid (GA3) and trans-zeatin ribside (t-ZR) content decreased with the reduction of temperature, with higher content in Latitude-40 than in Latitude-22. Chilling and freezing induced the up-regulation of C-repeat binding factor (ZjCBF), late embryogenesis abundant (ZjLEA3) and dehydration-responsive element binding (ZjDREB1) transcription factors in two genotypes, whereas those genes exhibited higher expression levels in Latitude-40, particularly under freezing temperature. These results suggested that zoysiagrass native to higher latitude exhibited higher freezing tolerance may attribute to the higher carbohydrates serving as energy reserves and stress protectants that stabilize cellular membranes. The phytohormones may serve signals in regulating plant growth, development and adaptation to low temperature as well as inducing the up-regulated ZjCBF, ZjLEA3 and ZjDREB1 expressions thus result in a higher cold tolerance.

Fruit ripening involves a complex interplay among plant hormones. Strawberry is a model for studies on non-climacteric fruit ripening. However, the knowledge on how plant hormones are involved in strawberry ripening is still limited. To understand hormonal actions in the ripening process, we performed genome-wide transcriptome and hormonal analysis for the five major hormones (abscisic acid and catabolites, auxins, cytokinins, gibberellins, and ethylene) in achenes and receptacles (flesh) at different ripening stages of the woodland strawberry Fragaria vesca. Our results demonstrate that the pre-turning stage (a stage with white flesh and red achenes defined in this study) is the transition stage from immature to ripe fruits. The combinatorial analyses of hormone content, transcriptome data, and exogenous hormone treatment indicate that auxin is synthesized predominantly in achenes, while abscisic acid (ABA), bioactive free base cytokinins, gibberellins, and ethylene are mainly produced in receptacles. Furthermore, gibberellin may delay ripening, while ethylene and cytokinin are likely involved at later stages of the ripening process. Our results also provide additional evidence that ABA promotes ripening, while auxin delays it. Although our hormone analysis demonstrates that the total auxin in receptacles remains relatively low and unchanged during ripening, our experimental evidence further indicates that ABA likely enhances expression of the endoplasmic reticulum-localized auxin efflux carrier PIN-LIKES, which may subsequently reduce the auxin level in nucleus. This study provides a global picture for hormonal regulation of non-climacteric strawberry fruit ripening and also evidence for a possible mechanism of ABA and auxin interaction in the ripening process.

A number of scientific reports published to date contain data on endogenous levels of various phytohormones in potato ( Solanum tuberosum L.) but a complete cytokinin profile of potato tissues, that would include data on all particular molecular forms of cytokinin, has still been missing. In this work, endogenous levels of all analytically detectable isoprenoid cytokinins, as well as the auxin indole-3-acetic acid (IAA), and abscisic acid (ABA) have been determined in shoots and roots of 30 day old in vitro grown potato (cv. Désirée). The results presented here are generally similar to other data reported for in vitro grown potato plants, whereas greenhouse-grown plants typically contain lower levels of ABA, possibly indicating that in vitro grown potato is exposed to chronic stress. Cytokinin N -glucosides, particularly N 7-glucosides, are the dominant cytokinin forms in both shoots and roots of potato, whereas nucleobases, as the bioactive forms of cytokinins, comprise a low proportion of cytokinin levels in tissues of potato. Differences in phytohormone composition between shoots and roots of potato suggest specific patterns of transport and/or differences in tissue-specific metabolism of plant hormones. These results represent a contribution to understanding the hormonomics of potato, a crop species of extraordinary economic importance.

In this study, we investigated the changes in the distribution and regulation of endogenous hormones in Phyllostachys edulis ‘Pachyloen’ during bamboo shooting. Enzyme-linked immunosorbent assay was used to measure the mass fractions of indole-3-acetic acid (IAA), gibberellic acid (GA), zeatin riboside (ZR), and abscisic acid (ABA) in rhizomes, shoots, and maternal bamboo organs during shoot sprouting, shoot growth, and new-bamboo formation. Measurements were compared among bamboo parts and developmental periods. The overall mass fractions of IAA and ABA were significantly higher than those of ZR and GA, driven by differences among bamboo parts and developmental periods. The abundance of each endogenous hormone varied among bamboo parts and developmental periods. During bamboo shooting, ABA had the highest mass fraction in all bamboo parts sampled, followed by IAA, GA, and ZR. Among bamboo parts, rhizomes had more IAA, ZR, and GA than the other parts, but significantly less ABA. Winter shoots had higher ZR: IAA and GA: IAA ratios than rhizomes and maternal bamboo organs. During shoot growth, ABA was the most abundant hormone in rhizomes and maternal bamboo organs, followed by IAA, ZR, and GA. In contrast, IAA was the most abundant hormone in spring shoots, followed by ABA, ZR, and GA. Maternal bamboo organs had a significantly higher ZR: GA ratio, and significantly lower IAA: ABA, ZR: ABA, and GA: ABA ratios than rhizomes. Spring shoots had significantly higher IAA: ABA, ZR: ABA, and GA: ABA ratios than rhizomes and maternal bamboo organs; significantly higher ZR mass fractions, and ZR: GA and ZR: IAA ratios and significantly lower ABA mass fractions than rhizomes; and significantly higher GA: IAA ratio than maternal bamboo organs. During new-bamboo formation, ABA was the most abundant hormone in rhizomes, winter shoots, and maternal bamboo organs, followed by IAA, ZR, and GA. Maternal bamboo organs had significantly lower IAA mass fractions and significantly higher ABA mass fractions than rhizomes and new bamboo tissue. IAA and ABA abundances exhibited an inverse relationship in rhizomes and maternal bamboo organs. GA: ABA and GA: IAA ratios decreased gradually and other hormone ratios exhibited parabolic trends over the bamboo-shooting period, with the highest ratios observed in new bamboo tissues. Overall, the coordination or antagonism among endogenous hormones plays a key regulatory role in bamboo shoot growth. The formation of thick walls in P . edulis ‘Pachyloen’, one of its major traits, may be partially attributed to the relatively high IAA and ZR and low GA mass fractions.

Plant responses to abiotic stresses are coordinated by arrays of growth and developmental programs. Phytohormones such as abscisic acid (ABA) and indole-3-acetic acid (IAA) play critical roles in developmental progresses and environmental responses through complex signalling networks. However, crosstalk between the two hormones at the biosynthesis level remains largely unknown. Here, we report that carotenoid-deficient mutants ( phs1 , phs2 , phs3 - 1 , phs4 , and PDS -RNAi transgenic rice) were impaired in the biosynthesis of ABA and IAA. Under drought conditions, phs3 - 1 and PDS -RNAi transgenic rice showed larger stomata aperture and earlier wilting compared to the wild type at both seedling and panicle developmental stage. Interestingly, these carotenoid-deficient lines showed increased cold resistance, which was likely due to the combined effects of reduced IAA content, alleviated oxidative damage and decreased membrane penetrability. Furthermore, we found that IAA content was significantly declined in rice treated with fluridone (a carotenoid and ABA biosynthesis inhibitor), and expression of auxin synthesis and metabolism-related genes were altered in the fluridone-treated rice similar to that in the carotenoid-deficient mutants. In addition, exogenous IAA, but not ABA, could restore the dwarf phenotype of phs3 - 1 and PDS -RNAi transgenic rice. These results support a crosstalk between ABA and IAA at the biosynthesis level, and this crosstalk is involved in development and differentially affects drought and cold tolerance in rice.