Class Of Plant Growth Regulators Research Articles

Growth and transcriptional response of wheat and rice to the tertiary amine BMVE.

Seed vigor is largely a product of sound seed development, maturation processes, genetics, and storage conditions. It is a crucial factor impacting plant growth and crop yield and is negatively affected by unfavorable environmental conditions, which can include drought and heat as well as cold wet conditions. The latter leads to slow germination and increased seedling susceptibility to pathogens. Prior research has shown that a class of plant growth regulators called substituted tertiary amines (STAs) can enhance seed germination, seedling growth, and crop productivity. However, inconsistent benefits have limited STA adoption on a commercial scale. We developed a novel seed treatment protocol to evaluate the efficacy of 2-(N-methyl benzyl aminoethyl)-3-methyl butanoate (BMVE), which has shown promise as a crop seed treatment in field trials. Transcriptomic analysis of rice seedlings 24 h after BMVE treatment was done to identify the molecular basis for the improved seedling growth. The impact of BMVE on seed development was also evaluated by spraying rice panicles shortly after flower fertilization and subsequently monitoring the impact on seed traits. BMVE treatment of seeds 24 h after imbibition consistently improved wheat and rice seedling shoot and root growth in lab conditions. Treated wheat seedlings grown to maturity in a greenhouse also resulted in higher biomass than controls, though only under drought conditions. Treated seedlings had increased levels of transcripts involved in reactive oxygen species scavenging and auxin and gibberellic acid signaling. Conversely, several genes associated with increased reactive oxygen species/ROS load, abiotic stress responses, and germination hindering processes were reduced. BMVE spray increased both fresh and mature seed weights relative to the control for plants exposed to 96 h of heat stress. BMVE treatment during seed development also benefited germination and seedling growth in the next generation, under both ambient and heat stress conditions. The optimized experimental conditions we developed provide convincing evidence that BMVE does indeed have efficacy in plant growth enhancement. The results advance our understanding of how STAs work at the molecular level and provide insights for their practical application to improve crop growth.

Sydnone Imines: A Novel Class of Plant Growth Regulators

An increase in the yield of the main cereal crops in the context of global climate changes requires additional impacts on plants. Natural and synthetic plant growth regulators (PGRs) are used to increase plant productivity and reduce the injury level caused by abiotic stressors. There is a growing need for novel highly effective plant growth stimulants to exhibit their effects at low doses and to not pose an environmental threat or injury to the crop quality. The derivatives of sydnone imine (SI), a mesoionic heterocycle possessing a 1,2,3-oxadiazole core, have been used as medicines until now but have not been used for agricultural applications. Some SI derivatives have recently been found to exhibit PGR properties. Herein, we report on the study of the PGR potential of nine SI derivatives bearing variable substituents at N(3), C(4), and N6 positions of the heterocycle designed to disclose the “molecular structure-PGR activity” relationship in this family. The SI derivatives were used in a wide concentration range (10−9–10−4 mol/L) for a pre-sowing treatment of winter wheat (Triticum aestivum L., two cultivars) and maize (Zea mays L., two hybrids) seeds in germinating experiments. All compounds were found to affect the growth of the axial organs of germinants, with the growth-stimulating or -inhibitory effect as well as its rate being considerably different for wheat and maize and, in many cases, also for roots and shoots. In addition, a pronounced concentration dependence of the effect was disclosed for many cases. The features of the molecular structure of SIs affecting their growth-regulating properties were elucidated. Compounds 4, 6, 7, and 8, which had exhibited a growth-promoting effect in germinating experiments, were used at appropriate concentrations for pot experiments on the same crops. For all compounds, the experiments showed a stimulating effect on the growth of roots (up to 80%), shoots (up to 112%), leaf area (up to 113%), fresh weights of roots (up to 83%), and aerial parts of the plants (up to 87%) or only on some of these parameters. The obtained results show a healthy outlook for the use of SI derivatives as promoting agents for improving the growth of cereal crop plants.

Applications of Cytokinins in Horticultural Fruit Crops: Trends and Future Prospects

Cytokinins (CKs) are a chemically diverse class of plant growth regulators, exhibiting wide-ranging actions on plant growth and development, hence their exploitation in agriculture for crop improvement and management. Their coordinated regulatory effects and cross-talk interactions with other phytohormones and signaling networks are highly sophisticated, eliciting and controlling varied biological processes at the cellular to organismal levels. In this review, we briefly introduce the mode of action and general molecular biological effects of naturally occurring CKs before highlighting the great variability in the response of fruit crops to CK-based innovations. We present a comprehensive compilation of research linked to the application of CKs in non-model crop species in different phases of fruit production and management. By doing so, it is clear that the effects of CKs on fruit set, development, maturation, and ripening are not necessarily generic, even for cultivars within the same species, illustrating the magnitude of yet unknown intricate biochemical and genetic mechanisms regulating these processes in different fruit crops. Current approaches using genomic-to-metabolomic analysis are providing new insights into the in planta mechanisms of CKs, pinpointing the underlying CK-derived actions that may serve as potential targets for improving crop-specific traits and the development of new solutions for the preharvest and postharvest management of fruit crops. Where information is available, CK molecular biology is discussed in the context of its present and future implications in the applications of CKs to fruits of horticultural significance.

Plant Perception of Light: The role of indoleamines in Scutellaria species

Light mediates plant growth through diverse mechanisms and signaling networks including plant growth regulators (PGRs). We hypothesized that a novel class of PGRs, the indoleamines, are plant signaling molecules that perceive changes in light composition and initiate a cascade of metabolic responses. We used three Scutellaria model species (skullcap): S. lateriflora, S. galericulata and S. racemosa that produce high levels of melatonin and serotonin to investigate this hypothesis. Axenic Scutellaria cultures were exposed to red, blue, green or full spectrum white light spectra provided by light emitting diode (LED) lighting systems, or daylight fluorescent bulbs. Melatonin (MEL), serotonin (5HT), abscisic acid (ABA), auxin (IAA), and jasmonic acid (JA), were quantified by liquid chromatography with tandem mass spectrometry. Melatonin was detected consistently in plants grown under blue light in all species of Scutellaria. In S. galericulata, significant quantities of ABA were detected in plants grown under white light but not detected in plants grown under other light spectra. In timeline studies of S. racemosa plants exposed to limited red or blue light spectra had significantly reduced levels of tryptamine (TRM), 5HT and MEL in the shoots initially but melatonin was detected after 12 hours and quantifiable amounts of 5HT were detected after 7 days. Supplementation of the culture medium with MEL or 5HT did not change the pattern of MEL in blue light grown cultures but did change patterns of 5HT accumulation. 5HT was highest in plants grown under red light immediately after culture and decreased over 7 days. These data indicate that the relative amounts of MEL and 5HT are responsive to light spectra and redirect metabolic resources to enable plant adaptations to changing environments.

Gibberellic Acid-Priming Promotes Fluoride Tolerance in a Susceptible Indica Rice Cultivar by Regulating the Antioxidant and Phytohormone Homeostasis

Excessive utilization of groundwater for anthropogenic purposes has led to severe depletion of the water table, resulting in contamination of fluorides from the mineral bed. Irrigation of rice seedlings with such fluoride-infested water leads to high fluoride bioaccumulation and compromised growth physiology. In the present study, we showed that the priming of seeds with gibberellic acid 3 (GA) alleviated prolonged fluoride-induced toxicity in the fluoride-susceptible indica rice cultivar, IR-64 (grown in soil) by reducing the accumulation of the xenobiotic within the seedling biomass. The primed seeds showed improved percentage of germination during fluoride stress compared to the non-primed seeds. The stressed seedlings grown from the GA-primed seeds exhibited increased endogenous accumulation of GA and the auxin, indole-3-acetic acid which stimulated shoot and root growth and relative water content, compared to the stressed seedlings germinated from the non-primed seeds. GA-priming reduced the chlorophyll degradation, affected the homeostasis of the accessory pigments and lowered the electrolyte leakage during stress. Upon GA-priming, the fluoride-induced oxidative stress was ameliorated by an increase in proline, anthocyanin, flavonoid and total phenolic contents, reducing power, total antioxidant capacity and DPPH-radical scavenging activity. The altered activity of the antioxidative enzymes like catalase, ascorbate peroxidase and guaiacol peroxidase also enabled efficient H2O2 scavenging in the stressed plants germinated from the primed seeds. Thus, seed pre-treatment with GA promoted fluoride tolerance by activating the antioxidant machinery and elevating the endogenous level of the two most important classes of plant growth regulators, gibberellic acid and auxin.

Alkamides: a new class of plant growth regulators linked to humic acid bioactivity

BackgroundThe use of humic substances as plant biostimulants has been increasingly attracting farmers and stunning researchers. The ability of these substances to enhance root growth by changing root architecture is often linked to their hormonal activities, such as auxin effects and nitric oxide production. Humeomics accesses the molecular constituents of humic substances, revealing the importance of alkyl components because of their conformations and chemical activities. Here, we describe the alkamides present in humic acids and compare their bioactivities using plasma membrane H+-ATPase activity level as a biochemical marker.MethodsHumic acids isolated from vermicompost were analyzed using 13C and 15N nuclear magnetic resonance spectroscopy. The unbound fraction was extracted with ethyl acetate and submitted to gas chromatography coupled to mass spectrometry to detect the presence of N-isopropyldecanamide. We synthesized N-isopropyldecanamide and treated maize seedlings for 7 and 15 days with different concentrations. The root growth and plasma membrane H+-ATPase activity were monitored. Nitric oxide accumulation in the lateral roots was imaged using 4,5-diaminofluorescein diacetate. The results were compared with those obtained for seedlings treated with humic acids isolated from vermicompost.ResultsThe amide functional group produced the only nitrogen signal in the 15N humic acid resonance spectrum and similar alkamide moieties were found in the unbound humic extract through comparisons using gas chromatography coupled to mass spectrometry. The synthesis of N-isopropyldecanamide had few steps and produced a high yield (86%). The effects of N-isopropyldecanamide on root growth were concentration dependent. High concentrations (10−4 M) enhanced root growth after 15 day of diminishing shoot biomass. However, low concentrations (10−8 M and 10−6 M) promoted root growth at 7 and 15 days, similar to the humic acid-induced plasma membrane H+-ATPase activity. Both N-isopropyldecanamide and humic acids enhanced nitric oxide accumulation during lateral root emergence.ConclusionWe described for the first time the effects of N-isopropyldecanamide on the plasma membrane H+-ATPase activity in maize seedling roots and compared its effects with those caused by humic acids. N-Isopropyldecanamide was detected in the unbound fraction of the humic supramolecular assembly, indicating that the putative hormone-like effects of these substances result also from the presence of this new class of plant regulators, in addition to other molecules.

Water-soluble pillar[5]arenes: A new class of plant growth regulators

It is highly valuable to develop bifunctional chemical fertilizers that can both regulate plant growth and reduce the toxicity of pesticides. Here we report three water-soluble pillar[5]arenes WP5-1, WP5-2 and WP5-3 established as efficient plant growth regulators for wheat to efficiently improve the development of buds and roots in the seedling cultivation stage. Moreover, as macrocyclic hosts for the poisoning herbicide paraquat, WP5-2 and WP5-3 can also be employed to reduce its toxicity based on host–guest interactions, as confirmed by cell viability experiments towards HEK 293 and Raw 264.4 cell lines.

Kinetin Alleviates UV-B-Induced Damage in Solanum lycopersicum: Implications of Phenolics and Antioxidants

Cytokinins, a class of plant growth regulators, are known to regulate several plant developmental processes and may play a significant role in protecting them against abiotic stresses. Thus, this study was focused on the effect of kinetin (KN, 10 µM) treatment on phenylpropanoid pathway: PAL activity, phenolics, flavonoids, and anthocyanins contents, and oxidative stress biomarkers, antioxidant potential, and growth in tomato seedlings exposed to UV-B (UV-B1, ambient + 1.2 kJ m−2 day−1 and UV-B2, ambient + 2.4 kJ m−2 day−1) stress. UV-B exposure to KN untreated seedlings caused substantial increase in reactive oxygen species contents: superoxide radical and hydrogen peroxide (H2O2), and oxidative damage biomarkers: lipid peroxidation and electrolyte leakage in a dose-dependent manner, despite increased antioxidant potential: super oxide dismutase (SOD), peroxidase (POD), catalase (CAT) and glutathione-S-transferase (GST) activity, and radical scavenging capacity (DPPH activity), PAL activity, total phenolics, flavonoids and anthocyanins contents. The seedlings pre-treated with KN and subsequently exposed to UV-B exhibited substantial increase (i) in antioxidant potential: SOD, POD, CAT and GST activity, and DPPH activity and (ii) PAL activity which led to a further rise in total phenolics, UV-B screening pigments (flavonoids) and anthocyanins and hence, significant lowering in oxidative stress biomarkers was noticed. The overall results show that KN pre-treatment significantly alleviated UV-B-induced damaging effects in tomato seedlings by regulating phenolics and antioxidants.

Improvement in photosynthesis, seed yield and protein content of common bean (Phaseolus vulgaris) by foliar application of 24-epibrassinolide under drought stress

Brassinosteroids (BRs), as a class of plant growth regulators, have been shown to affect different physiological traits of plants and counteract various stresses. We studied the possibility of increasing seed and protein yields of two genotypes of common bean (Phaseolus vulgaris L.) with the exogenous application of 24-epibrassinolide (EBL) in an experiment conducted during 2016 and 2017. Two levels of irrigation (optimal and drought stress) were applied to the main plots, and two genotypes of common bean (cv. Kusha and genotype COS16) and four concentrations of EBL (0, 2, 4 and 6 μm) were allocated to subplots in a factorial arrangement. At the flowering stage, drought stress was applied and bean plants were sprayed with EBL. The results indicate that drought stress reduced leaf area, yield components, seed yield and protein content. Moreover, substantial increase in intercellular CO2 concentration and decrease in transpiration rate, stomatal conductance and net photosynthetic rate were also recorded. However, exogenous application of EBL remarkably improved gas exchange attributes, leaf area, yield components, seed yield and protein content both under optimal irrigation and drought-stress conditions. Analysis of regression showed that, under both water-supply conditions, genotype COS16 would have highest seed yield when receiving 4.05 and 4.52 µm EBL, and cv. Kusha would have the highest seed yield by receiving 3.27 and 3.62 µm EBL. Therefore, EBL can be used as a plant growth regulator to enhance drought tolerance and minimise yield loss of common bean caused by water deficits.

Ameliorating Nickel Stress by Jasmonic Acid Treatment in Zea mays L.

Plants need various micro and macronutrients for their growth and metabolism. Of these nickel (Ni) plays a role of micronutrient but causes adverse effects when present above optimum level. To combat such situations plants possess different growth regulators. Jasmonates are a class of plant growth regulators modulating various growth and physiological responses in plants. Aiming to evaluate the effect of nickel and jasmonic acid on growth and antioxidant enzymes Superoxide distmutase (SOD), Catalse (CAT), Ascorbate peroxidase (APX), Guaiacol peroxidase (GPX) and glutathione reductase (GR), seeds of Zea mays L. were sown in field after giving presowing treatment of NiSO4 · 6H2O (8 mM), jasmonic acid JA (10–6, 10–8 and 10–10 M) alone and JA (10–6, 10–8 and 10–10 M) in 1: 1 combination with NiSO4 · 6H2O (8 mM) in plant conservatory, Punjabi University, Patiala, Punjab, India. Plants of each treatment group were then subjected to spraying treatment with the respective treatment solutions at regular intervals of 22 days up to 66 days after sowing (DAS). The present findings signified reduced growth with Ni treatment but co-application of JA alleviated the effect of nickel through activity of antioxidant enzymes.

Kinetin Regulates UV-B-Induced Damage to Growth, Photosystem II Photochemistry, and Nitrogen Metabolism in Tomato Seedlings

Cytokinins are a class of plant growth regulators that regulate several developmental processes in plants, and recently their role in counteracting the deleterious effects of abiotic stresses has been noted. The impacts of kinetin (10 µM, KN; an artificial cytokinin) on growth, photosystem II photochemistry, and nitrogen metabolism in tomato seedlings exposed to two levels (UV-B1, ambient+ 1.2 kJ m−2 day−1, and UV-B2, ambient+ 2.4 kJ m−2 day−1) of enhanced UV-B radiation were analyzed under open field condition. The growth, pigment contents, carbonic anhydrase activity, photosynthetic O2 yield, and values of chlorophyll a fluorescence parameters: F v/F 0, F v/F m or φP0, ψ 0, φE 0, and PIABS declined, whereas the values of energy flux parameters (ABS/RC, TR0/RC, ET0/RC, and DI0/RC) of PS II, efficiency of water splitting complex (F 0/F v), and respiratory rate of O2 uptake increased under UV-B stress. Likewise, UV-B exposure at both doses significantly inhibited the activity of enzymes involved in nitrogen metabolism: nitrate reductase, nitrite reductase, glutamine synthetase, and glutamate synthase. In contrast, an enhancing effect on glutamate dehydrogenase activity was observed under UV-B stress. Exogenous KN resulted in a significant attenuation in UV-B-induced negative effects on growth, pigments, photosynthesis, and nitrogen metabolism. The study concludes that exogenous KN improved the growth performance of tomato seedlings by attenuating the damaging effects of UV-B radiation on photochemistry of PS II and nitrogen metabolism, and the alleviating effect against the low dose (UV-B1) of UV-B was more pronounced.

24-Epibrassinolide Acts as a Growth-Promoting and Resistance-Mediating Factor in Strawberry Plants

A new approach to improve the yield and quality of agricultural crops is the use of plant growth regulators. Brassinosteroids, as a class of plant growth regulators, have been shown to affect different physiological traits of plants. The effect of 24-epibrassinolide (EBL) on some photosynthesis-related physiological traits and stress-related enzyme activity was investigated. Strawberry (Fragaria × ananassa cv. Sabrosa) seedlings grown in a hydroponic medium were sprayed with 1 and 4 µM EBL and evaluated for different physiological attributes. EBL at the 1 µM level significantly enhanced leaf photosynthetic pigments, gas exchange and net photosynthesis rate, and soluble sugar and starch content but decreased stomatal resistance and intercellular CO2 content. At the 4 µM level, EBL had no effects on photosynthesis-related activities. EBL, in a concentration dependent manner, enhanced the activity of phenylalanine ammonia-lyase, polyphenol oxidase, and peroxidase. Interestingly, the results showed that EBL, at low concentrations, acts as a growth-promoting and relatively stress-mediating agent and strongly enhances stress resistance at higher doses.

Evidence that KARRIKIN-INSENSITIVE2 (KAI2) Receptors may Perceive an Unknown Signal that is not Karrikin or Strigolactone.

The α/β-hydrolases KAI2 and D14 are paralogous receptors for karrikins and strigolactones, two classes of plant growth regulators with butenolide moieties. KAI2 and D14 act in parallel signaling pathways that share a requirement for the F-box protein MAX2, but produce distinct growth responses by regulating different members of the SMAX1-LIKE/D53 family. kai2 and max2 mutants share seed germination, seedling growth, leaf shape, and petiole orientation phenotypes that are not found in d14 or SL-deficient mutants. This implies that KAI2 recognizes an unknown, endogenous signal, herein termed KAI2 ligand (KL). Recent studies of ligand-specificity among KAI2 paralogs in basal land plants and root parasitic plants suggest that karrikin and strigolactone perception may be evolutionary adaptations of KL receptors. Here we demonstrate that evolutionarily conserved KAI2c genes from two parasite species rescue multiple phenotypes of the Arabidopsis kai2 mutant, unlike karrikin-, and strigolactone-specific KAI2 paralogs. We hypothesize that KAI2c proteins recognize KL, which could be an undiscovered hormone.

Gibberellin-like effects of KAR1 on dormancy release of Avena fatua caryopses include participation of non-enzymatic antioxidants and cell cycle activation in embryos.

Main conclusionThe induction of dormancy release and germination ofAvena fatuacaryopses by KAR1involves ABA degradation to phaseic acid. Both, KAR1and GA3, control the AsA–GSH cycle, DNA replication and accumulation of β-tubulin in embryos before caryopses germination.Avena fatua caryopses cannot germinate in darkness at 20 °C because of dormancy, but karrikinolide-1 (KAR1), a compound in plant-derived smoke, and gibberellic acid (GA3) induced an almost complete germination. The radicle protrusion through the coleorhiza was preceded by increased water uptake, rupture of coat, increased embryo size and coleorhiza length as well as coleorhiza protrusion through covering structures. The stimulatory effect of KAR1 was correlated with the reduced content of abscisic acid (ABA) and an increase in phaseic acid (PA) in embryos from caryopses before coleorhiza protrusion. Two non-enzymatic antioxidants, ascorbate (AsA) and reduced glutathione (GSH), did not affect the germination of dormant caryopses, but in the presence of KAR1 or GA3 they only slightly delayed the germination. The stimulatory effect of KAR1 or GA3 on the final germination percentage was markedly antagonized by lycorine, an AsA biosynthesis inhibitor. KAR1 and GA3 applied during caryopses imbibition resulted in increases of AsA, dehydroascorbate (DHA) and GSH, but reduced the embryos’ oxidized glutathione (GSSG) content. Furthermore, both KAR1 and GA3 induced an additional ascorbate peroxidase (APX) isoenzyme and increased the glutathione reductase (GR) activity. Both compounds stimulated β-tubulin accumulation in radicle+coleorhiza (RC) and plumule+coleoptile (PC), and enhanced the transition from G1 to S and also from S to G2 phases. The comparison of the effects produced by KAR1 and GA3 shows a similar action; thus the KAR1 effect may not be specific. The study provides new data regarding the mechanism with which KAR1, a representative of a novel class of plant growth regulators, regulates dormancy and germination of caryopses.

Synthesis, X-ray structure determination and germination studies on some smoke-derived karrikins

The discovery of the karrikin class of plant growth regulators (PGRs) is a milestone accomplishment in plant biochemistry and physiology, with significant potential in agriculture and horticulture. These compounds have in common a fused furano-pyran ring system featuring various permutations of methyl substitution. Chief amongst these compounds is karrikinolide (KAR1), identified as the key germination stimulant present in plant-derived smoke, which together with five other closely-related structures (KAR2–KAR6) make up the karrikin class of PGRs. By contrast, the germination inhibitor 3,4,5-trimethyl-2(5H)-furanone has also been identified in plant-derived smoke. Various synthetic endeavours have been undertaken for structure–activity relationship study purposes as well as to probe the molecular mechanics of these compounds. In this study, syntheses of KAR1, KAR3 and S-KAR1 were carried out and their structures verified by X-ray crystallography. Effects on germination were measured against the inhibitor 3,4,5-trimethyl-2(5H)-furanone in Grand Rapids lettuce seeds. X-ray crystallographic data and germination promotory activity for S-KAR1 are described for the first time.

Effect of Jasmonic Acid on Photosynthetic Pigments and Stress Markers in <i>Cajanus cajan</i> (L.) Millsp. Seedlings under Copper Stress

Jasmonates are class of plant growth regulators act as signal molecule that intercede various components in physiological and metabolic regulation, stress responses and possibly communication through signal transduction. Oxidative stress due to heavy metal exposure stimulates synthesis and activity of antioxidant metabolites and enhances antioxidant enzyme activities that could protect plant tissues. The aim of this study was to investigate the exogenous effect of JA at seed level which can transduce throughout seedling growth and regulate antioxidant activities such as superoxide dismutase (SOD; EC 1.15.1.1) and guaiacol peroxidase (POD; EC 1.11.1.7) in 12 days old seedlings of pigeon pea (Cajanus cajan (L.) Millsp.) in presence and/or absence of copper. The activity of SOD and POD increased significantly in presence of Cu2+ after seed priming with JA. JA also helps in chlorophyll and carotenoid accumulation and neutralizes the toxic effect of Cu2+ on seedlings. This is the first report of JA effect on photosynthetic pigment accumulation and H2O2 mitigating enzymes i.e. SOD and POD and it could be recommended that seed priming with JA help in ameliorating toxic effect of Cu2+.

Early increased expression of a cyclin-dependant protein kinase (LtCDKA1;1) during inflorescence initiation of the long day grass Lolium temulentum.

Knowing where and when different genes express at the shoot apex during the transition to flowering will help in understanding this developmental switch. The CDKA family of serine/threonine kinase genes are appropriate candidates for such developmental switching as they are involved in the regulation of the G1/S and G2/M boundaries of the cell cycle (see review by Dudits et al. 2007) and so could regulate increases of cell division associated with flowering. Furthermore, in rice stems the gibberellin (GA) class of plant growth regulators rapidly upregulate CDKA expression and cell division. Thus, CDKA expression might be linked to the florigenic action of GA as a photoperiodically-generated, signal. For the grass Lolium temulentum L., we have isolated an LtCDKA1;1 gene, which is upregulated in shoot apices collected soon after the start of a single florally inductive long day (LD). In contrast to weak expression of LtCDKA1;1 in the vegetative shoot apex, in situ and PCR-based mRNA assays and immunological studies of its protein show very rapid increases in the apical dome at the time that florigenic signals arrive at the apex (<6h after the end of the LD). By ~54h LtCDKA1;1 mRNA is localised to the floral target cells, the spikelet primordia. Later both LtCDKA1;1 mRNA and protein are most evident in floret meristems. Only ~10% of cells within the apical dome are dividing at any time but the LD increase in LtCDKA1;1 may reflect an early transient increase in the mitotic index (Jacqmard et al. 1993) as well as a later increase when spikelet primordia form. Increased expression of an AP1-like gene (LtMADS2) follows that of LtCDKA1;1. Overall, LtCDKA1;1 is a useful marker of both early florigenic signalling and of later morphological/developmental aspects of the floral transition.

Integration of shot-gun proteomics and bioinformatics analysis to explore plant hormone responses

BackgroundMultidimensional protein identification technology (MudPIT)-based shot-gun proteomics has been proven to be an effective platform for functional proteomics. In particular, the various sample preparation methods and bioinformatics tools can be integrated to improve the proteomics platform for applications like target organelle proteomics. We have recently integrated a rapid sample preparation method and bioinformatics classification system for comparative analysis of plant responses to two plant hormones, zeatin and brassinosteroid (BR). These hormones belong to two distinct classes of plant growth regulators, yet both can promote cell elongation and growth. An understanding of the differences and the cross-talk between the two types of hormone responses will allow us to better understand the molecular mechanisms and to identify new candidate genes for plant engineering.ResultsAs compared to traditional organelle proteomics, the organelle-enrichment method both simplifies the sample preparation and increases the number of proteins identified in the targeted organelle as well as the entire sample. Both zeatin and BR induce dramatic changes in signaling and metabolism. Their shared-regulated protein components indicate that both hormones may down-regulate some key components in auxin responses. However, they have shown distinct induction and suppression of metabolic pathways in mitochondria and chloroplast. For zeatin, the metabolic pathways in sucrose and starch biosynthesis and utilization were significantly changed, yet the lipid biosynthesis remained unchanged. For BR, lipid biosynthesis and β-oxidation were both down-regulated, yet the changes in sucrose and starch metabolism were minor.ConclusionsWe present a rapid sample preparation method and bioinformatics classification for effective proteomics analysis of plant hormone responses. The study highlighted the largely differing response to zeatin and brassinosteroid by the metabolic pathways in chloroplast and mitochondria.

Simultaneous determination of different endogenetic plant growth regulators in common green seaweeds using dispersive liquid–liquid microextraction method

A simple and rapid HPLC-based method was developed for simultaneous determination of major classes of plant growth regulators (PGRs) in Monostroma and different species of Ulva. The plant growth regulators determined included gibberellic acid (GA(3)), indole-3-acetic acid (IAA), abscisic acid (ABA), indole-3-butyric acid (IBA), salicylic acid and kinetin riboside (KR) and their respective elution time was 2.75, 3.3, 3.91, 4.95, 5.39 and 6.59 min. The parameters optimized for distinct separation of PGRs were mobile phase (60:40 methanol and 0.6% acetic acid in water), column temperature (35°C) and flow rate (1ml/min). This method presented an excellent linearity (0.2-100μg/ml) with limit of detection (LOD) as 0.2μg/ml for ABA, 0.5μg/ml for KR and salicylic acid, and 1μg/ml for IAA, IBA and GA(3). The precision and accuracy of the method was evaluated after inter and intra day analysis in triplicates. The effect of plant matrix was compensated after spiking and the resultant recoveries estimated were in the range of 80-120%. Each PGR thereby detected were further characterized by ESI-MS analysis. The method optimized in this study determined IBA along with IAA for the first time in the seaweed species investigated except Ulva linza where the former was not detected. In all the species studied, ABA level was detected to be the highest while kinetin riboside was the lowest. In comparison to earlier methods of PGR analysis, sample preparation and analysis time were substantially reduced while allowing determination of more classes of PGRs simultaneously.

Trichoderma harzianum strain T-22 induces changes in phytohormone levels in cherry rootstocks (Prunus cerasus × P. canescens)

The aim of this research was to explain the direct plant growth-promoting activity of Trichoderma harzianum strain T-22 (T22), hypothesizing the involvement of different classes of plant growth regulators. Seven days after the transfer to root-inducing medium, in vitro-cultured shoots of GiSeLa6® (Prunus cerasus × P. canescens) were inoculated with T22. Root and shoot growth were significantly affected by T22 (+76 and +61%, respectively). Ten days after inoculation, the levels of indole-3-acetic acid (IAA), trans-zeatin riboside (t-ZR), dihydrozeatin riboside (DHZR), gibberellic acid (GA3) and abscisic acid (ABA) were analyzed by high performance liquid chromatography coupled with mass spectrometry. The results showed that after T22-inoculation, IAA and GA3 significantly increased in both leaves (+49 and +71%, respectively) and roots (+40 and +143%, respectively) whereas t-ZR decreased (−51% in leaves and −37% in roots). Changes in DHZR were observed in T22-inoculated roots (−32%) but not in leaves, whereas the levels of ABA did not differ between the two treatments. The extraction method allowed the simultaneous extraction of phytohormones. There is evidence that the change in phytohormone levels is one of the direct mechanism by which T22 promotes rooting and shoot growth, with notable advantages for rootstock production during nursery processes.