Induce Plant Growth Research Articles

Combined effect of ethylene- and salicylic acid-signaling insensitive mutation on Arabidopsis response to low temperature

The roles of ethylene (ET) or salicylic acid (SA) in plant response to low temperature (LT, 5 °C) have been implicated. However, the combined effect of ET- and SA-signaling on plant growth and metabolism under LT remains to be evaluated. In this study, we comparatively analyzed the response of Arabidopsis ethylene insensitive (ein) 2-1 (an ET insensitive mutant), nonexprressor of pathogenesis relative (npr)1-1 (an SA insensitive mutant) and double mutant ein2-1/npr1-1 plants to LT. The results show that a LT of 5 °C induced plant growth retardation to a less degree in ein2-1, an intermediate degree in npr1-1, but a much larger in ein2-1/npr1-1 compared to the wild-type (WT) plants. The LT susceptibility of the ein2-1/npr1-1 plants was correlated to a lower net photosynthetic rate and proline content, and a higher content of H2O2 and malondialdehyde and electrolyte leakage relative to the WT plants. Lower activities of superoxide dismutase, peroxidase, and catalase, as well as a lower glutathione content and a ratio of its reduced form to its oxidized form were also observed in the double mutant plants as compared with the WT plants. However, at normal conditions (23 °C), all the tested physiological and biochemical parameters were comparable between the ein2-1/npr1-1 and WT plants, and plant growth was even better in the double mutant than in the WT plants. On the contrary, most of the above-mentioned parameters were advantageous in the ein2-1 and npr1-1 plants over the WT plants under the LT conditions. These data suggest that a parallel function or physiological redundancy of nonexpressor of pathogenesis relative 1 and ethylene insensitive 2 existed in the Arabidopsis plant response to the LT. On the other hand, an interaction between ET- and SA-signaling occurred during this process.

Harpin Hpa1 Interacts with Aquaporin PIP1;4 to Promote the Substrate Transport and Photosynthesis in Arabidopsis.

Harpin proteins produced by plant-pathogenic Gram-negative bacteria are the venerable player in regulating bacterial virulence and inducing plant growth and defenses. A major gap in these effects is plant sensing linked to cellular responses, and plant sensor for harpin Hpa1 from rice bacterial blight pathogen points to plasma membrane intrinsic protein (PIP). Here we show that Arabidopsis AtPIP1;4 is a plasma membrane sensor of Hpa1 and plays a dual role in plasma membrane permeability of CO2 and H2O. In particular, AtPIP1;4 mediates CO2 transport with a substantial contribute to photosynthesis and further increases this function upon interacting with Hpa1 at the plasma membrane. As a result, leaf photosynthesis rates are increased and the plant growth is enhanced in contrast to the normal process without Hpa1-AtPIP1;4 interaction. Our findings demonstrate the first case that plant sensing of a bacterial harpin protein is connected with photosynthetic physiology to regulate plant growth.

Effect of hydrogen sulfide on D1 protein in wheat under drought stress

Drought usually induces plant growth inhibition and oxidative damage. This report showed the protections of hydrogen sulfide (H2S) against drought-induced damage in wheat, which was manifested in the better growth, higher relative water content (RWC), lower thiobarbituric acid-reactive substances (TBARS), and hydrogen peroxide (H2O2) as well as the increased activities of superoxide dismutase (SOD) and catalase (CAT). Drought often causes photosystem II (PS II) damage, which was observed in the decreased potential photochemical efficiency (F v/F m), actual photochemical efficiency (ΦPS II), photochemical quenching (qP), electron transfer rate (ETR), and increased non-photochemical quenching (qN), however, these effects could be alleviated by NaHS (H2S donor). D1 protein in PS II reaction center is the most sensitive target of PS II damage. Compared to water treatment, a higher level of transcription but less D1 protein and phosphorylated D1 protein was detected in wheat leaves when exposed to NaHS under drought stress, which may result from the higher expression of STN8 (catalyze D1 protein phosphorylation) and D1 protein degradation-related gene (Deg1, Deg5, Deg8, FtsH2, and FtsH5). These results suggested that H2S alleviated drought-induced PS II damage owing to fast D1 protein turnover rather than D1 protein content.

Genome Sequence of Rhizobacterium Serratia marcescens Strain 90-166, Which Triggers Induced Systemic Resistance and Plant Growth Promotion

The rhizobacterium Serratia marcescens strain 90-166 elicits induced systemic resistance against plant pathogens and herbivores and promotes plant growth under greenhouse and field conditions. Strain 90-166 secretes volatile compounds, siderophores, salicylic acid, and quorum-sensing autoinducers as bacterial determinants toward plant health. Herein, we present its draft genome sequence.

MB1533 is a Defensin-Like Antimicrobial Peptide from the Intracellular Meristem Endophyte of Scots Pine Methylobacterium extorquens DSM13060

Endophytes induce plant growth and protect host plants against abiotic and biotic stresses, such phytopathogenic bacteria and fungi. Here we explored the genome of plant growth-promoting, intracellular endophyte Methylobacterium extorquens DSM13060, isolated from bud meristems of Pinus sylvestris L., for antimicrobial peptides. A defensinlike antimicrobial peptide MB1533 was identified using computational and prediction models from the genome sequence. MB1533 was produced in Escherichia coli with a molecular weight of 6160.26 Da. The antimicrobial activity was tested against several strains of bacteria and yeasts, and the peptide had activity against the grampositive Staphylococcus aureus and Bacillus subtilis at 128 μg/ml. The potency of the peptide can be improved further by rational-design-techniques. MB1533 is the first defensin-like peptide identified from Methylobacterium genus and from bacterial endophytes, in general.

Transgenic Expression of a Functional Fragment of Harpin Protein Hpa1 in Wheat Represses English Grain Aphid Infestation

The harpin protein Hpa1 produced by the rice bacterial blight pathogen promotes plant growth and induces plant resistance to pathogens and insect pests. The region of 10–42 residues (Hpa110–42) in the Hpa1 sequence is critical as the isolated Hpa110–42 fragment is 1.3-7.5-fold more effective than the full length in inducing plant growth and resistance. Here we report that transgenic expression of Hpa110–42 in wheat induces resistance to English grain aphid, a dominant species of wheat aphids. Hpa110–42-induced resistance is effective to inhibit the aphid behavior in plant preference at the initial colonization stage and repress aphid performances in the reproduction, nymph growth, and instar development on transgenic plants. The resistance characters are correlated with enhanced expression of defense-regulatory genes (EIN2, PP2-A, and GSL10) and consistent with induced expression of defense response genes (Hel, PDF1.2, PR-1b, and PR-2b). As a result, aphid infestations are alleviated in transgenic plants. The level of Hpa110–42-induced resistance in regard to repression of aphid infestations is equivalent to the effect of chemical control provided by an insecticide. These results suggested that the defensive role of Hpa110–42 can be integrated into breeding germplasm of the agriculturally significant crop with a great potential of the agricultural application.

Mechanisms behind bacteria induced plant growth promotion and Zn accumulation in Brassica juncea

The growth and metal-extraction efficiency of plants exposed to toxic metals has been reported to be enhanced by inoculating plants with certain bacteria but the mechanisms behind this process remain unclear. We report results from glasshouse experiments on Brassica juncea plants exposed to 400mgZnkg−1 that investigated the abilities of Pseudomonas brassicacearum and Rhizobium leguminosarum to promote growth, coupled with synchrotron based μXANES analysis to probe Zn speciation in the plant roots. P. brassicacearum exhibited the poorest plant growth promoting ability, while R. leguminosarum alone and in combination with P. brassicacearum enhanced plant growth and Zn phytoextraction. Reduced growth in un-inoculated plants was attributed to accumulation of Zn oxalate and Zn sulfate in roots. In plants inoculated with P. brassicacearum the high concentration of Zn polygalacturonic acid in the root may be responsible for the stunted growth and reduced Zn phytoextraction. The improved growth and increased metal accumulation observed in plants inoculated with R. leguminosarum and in combination with P. brassicacearum was attributed to the storage of Zn in the form of Zn phytate and Zn cysteine in the root. When combined with the observation that both bacteria do not statistically improve B. juncea growth in the absence of Zn, this work suggests that bacteria-induced metal chelation is the key mechanism of plant growth promoting bacteria in toxicity attenuation and microbial-assisted phytoremediation.

Azospirillum brasilense ameliorates the response of Arabidopsis thaliana to drought mainly via enhancement of ABA levels.

Production of phytohormones is one of the main mechanisms to explain the beneficial effects of plant growth-promoting rhizobacteria (PGPR) such as Azospirillum sp. The PGPRs induce plant growth and development, and reduce stress susceptibility. However, little is known regarding the stress-related phytohormone abscisic acid (ABA) produced by bacteria. We investigated the effects of Azospirillum brasilense Sp 245 strain on Arabidopsis thaliana Col-0 and aba2-1 mutant plants, evaluating the morphophysiological and biochemical responses when watered and in drought. We used an in vitro-grown system to study changes in the root volume and architecture after inoculation with Azospirillum in Arabidopsis wild-type Col-0 and on the mutant aba2-1, during early growth. To examine Arabidopsis development and reproductive success as affected by the bacteria, ABA and drought, a pot experiment using Arabidopsis Col-0 plants was also carried out. Azospirillum brasilense augmented plant biomass, altered root architecture by increasing lateral roots number, stimulated photosynthetic and photoprotective pigments and retarded water loss in correlation with incremented ABA levels. As well, inoculation improved plants seed yield, plants survival, proline levels and relative leaf water content; it also decreased stomatal conductance, malondialdehyde and relative soil water content in plants submitted to drought. Arabidopsis inoculation with A. brasilense improved plants performance, especially in drought.

The importance of crop growth modeling to interpret the Δ14CO2 signature of annual plants

The 14C/C abundance in CO2(Δ14CO2) promises to provide useful constraints on regional fossil fuel emissions and atmospheric transport through the large gradients introduced by anthropogenic activity. The currently sparse atmospheric Δ14CO2 monitoring network can potentially be augmented by using plant biomass as an integrated sample of the atmospheric Δ14CO2. But the interpretation of such an integrated sample requires knowledge about the day‒to‒day CO2 uptake of the sampled plants. We investigate here the required detail in daily plant growth variations needed to accurately interpret regional fossil fuel emissions from annual plant samples. We use a crop growth model driven by daily meteorology to reproduce daily fixation of Δ14CO2 in maize and wheat plants in the Netherlands in 2008. When comparing the integrated Δ14CO2 simulated with this detailed model to the values obtained when using simpler proxies for daily plant growth (such as radiation and temperature), we find differences that can exceed the reported measurement precision of Δ14CO2(∼2‰). Furthermore, we show that even in the absence of any spatial differences in fossil fuel emissions, differences in regional weather can induce plant growth variations that result in spatial gradients of up to 3.5‰ in plant samples. These gradients are even larger when interpreting separate plant organs (leaves, stems, roots, or fruits), as they each develop during different time periods. Not accounting for these growth‒induced differences in Δ14CO2 in plant samples would introduce a substantial bias (1.5–2 ppm) when estimating the fraction of atmospheric CO2 variations resulting from nearby fossil fuel emissions.

The role of bacterial biofilms and surface components in plant-bacterial associations.

The role of bacterial surface components in combination with bacterial functional signals in the process of biofilm formation has been increasingly studied in recent years. Plants support a diverse array of bacteria on or in their roots, transport vessels, stems, and leaves. These plant-associated bacteria have important effects on plant health and productivity. Biofilm formation on plants is associated with symbiotic and pathogenic responses, but how plants regulate such associations is unclear. Certain bacteria in biofilm matrices have been found to induce plant growth and to protect plants from phytopathogens (a process termed biocontrol), whereas others are involved in pathogenesis. In this review, we systematically describe the various components and mechanisms involved in bacterial biofilm formation and attachment to plant surfaces and the relationships of these mechanisms to bacterial activity and survival.

Endophytic microorganisms from coffee tissues as plant growth promoters and biocontrol agents of coffee leaf rust

A total of 234 strains of endophytic bacteria (217) and fungi (17) from coffee tissues were evaluated for their potential to control coffee leaf rust (Hemileia vastatrix) and to promote the growth of coffee seedlings. None of the fungal strains induced plant growth or reduced disease severity. Bacterial strains 85G (Escherichia fergusonii), 161G, 163G, 160G, 150G (Acinetobacter calcoaceticus) and 109G (Salmonella enterica) increased plant growth; the maximum increase was induced by strain 85G. This strain in vitro produced phosphatase and indol acetic acid. In an exploratory assay to control rust on coffee leaf discs, nine bacterial strains: 64R, 137G, 3F (Brevibacillus choshinensis), 14F (S. enterica), 36F (Pectobacterium carotovorum), 109G (Bacillus megaterium), 115G (Microbacterium testaceum), 116G and 119G (Cedecea davisae) significantly reduced disease severity when applied 72 or 24h before challenging with the pathogen. Strains 3F, 14F, 109G, 115G, 119G, and 137G significantly reduced the severity of coffee leaf rust when compared to the diseased control in the seedling assay, when applied 72h before challenging with the pathogen. Strain 109G was the most effective in this assay. Urediniospore germination was reduced 66% by strain 3F. There was no correspondence between the organisms that promoted seedling growth and those that reduced coffee leaf rust severity on seedlings or leaf discs.

Biopotential of some Trichoderma spp. against cotton root rot pathogens and profiles of some of their metabolites

The antagonistic activity of five selected isolates of Trichoderma spp. (Trichoderma harzianum CCM340, Trichoderma koningii CCM341, Trichoderma longibranchiatumNRRL11236, Trichoderma viride DSM63065 and Trichoderma viride) against Fusarium oxysporum f.sp. vasinfectum and Rhizoctonia solani, the causal agents of root rot of cotton plants grown in saline and non-saline soil, was studied in vitro and in vivo. Results indicated that F. oxysporum and R. solani were mostly inhibited by T. viride and least inhibited by T. longibranchiatum NRRL11236. Greenhouse test showed that for both pathogens, T. koningii CCM341 gave the highest disease control percentage (100%) in saline and non-saline soil and that T. harzianum CCM340, T. longibrachiatum NRRL11236 and T. viride DSM63065 gave the same disease control percentage (100%) in non-saline soil. In addition, the effect of Trichoderma isolates on several growth parameters of cotton plants was also studied. On the other hand, study on metabolites such as amino acids (AA), fatty acids (FA) and plant growth hormones (PGH) produced by these Trichoderma isolates showed that T. viride was the highest in AA production and the only isolate that produced lauric acid (FA). The highest amount of gibberellic acid, indol-3-acetic acid and abscisic acid was produced by T. viride DSM63065, T. harzianum CCM340 and T. koningii CCM341, respectively. Also, the pH and temperature effects on Trichoderma mycelial growth were also evaluated. However, the application of Trichoderma spp. to soil infested with F. oxysporum and R. solani provided a good way for protection of cotton plants. Also,Trichoderma metabolites such as amino acids, fatty acids and plant growth hormones may be developed into several commercial biological control products to prevent development of several pathogenic fungi and / or to induce plant growth response. Evaluation of pH and temperature effects on Trichoderma isolates mycelial growth showed that Trichoderma strains were found to be able to display activities under a wider range of pH values and that they are mesophili. Key words: Fusarium oxysporum, Rhizoctonia solani, cotton growth parameters, biocontrol agent, salinity.

Synthesis and plant growth promoting activity of polyhydroxylated ketones bearing the 5α-hydroxy-6-oxo moiety and cholestane side chain

Three polyhydroxylated ketones bearing the 5α-hydroxy-6-oxo moiety were obtained from cholesterol. Two of them show plant growth promoting activity in the bean’s second internode bioassay. The obtained results indicate that the presence of the 5α-hydroxy-6-oxo moiety may be capable to induce plant growth promotion even the absence oxygenated functions in the side chain.

Effect of Trichoderma asperellum and arbuscular mycorrhizal fungi on cacao growth and resistance against black pod disease

Arbuscular mycorrhizal fungi (AMF) and members of the genus Trichoderma have emerged as promising groups of microbial inoculants that can induce plant growth and resistance to disease. This study aimed at investigating the potential of AMF and a strain (PR11) of Trichoderma asperellum to promote cacao growth and induce resistance against Phytophthora megakarya. Cacao seedlings were either non-inoculated, or inoculated with the saprophytic fungus T. asperellum and/or a mixture of two different mycorrhizal fungi, Gigaspora margarita and Acaulospora tuberculata. Eighteen weeks after planting, a series of morphological as well as biochemical changes, which are considered to be part of the plant defense response, were measured after a challenge inoculation of the leaves with zoospores of P. megakarya. Inoculation with AMF and T. asperellum alone was essential for the promotion of plant growth. Significant increase in plant height, root and shoot fresh weights, as well as phosphorous uptake was recorded in comparison to non-inoculated control plants. However, dual inoculation of cacao seedlings with T. asperellum and AMF did not always positively benefit the plants. Leaf inoculation showed variation among the treatments, with the lowest disease index (highest level of resistance) recorded in plants inoculated with either AMF or T. asperellum only. This came along with a high synthesis of amino acids and phenolic compounds in both healthy and infected leaves, suggesting that these metabolites are implicated in disease resistance.

The shade avoidance syndrome: A non-Markovian stochastic growth model

Plants at high population density compete for light, showing a series of physiological responses known as the shade avoidance syndrome. These responses are controlled by the synthesis of the hormone auxin, which is regulated by two signals, an environmental one and an internal one. Considering that the auxin signal induces plant growth after a time lag, this work shows that plant growth can be modelled in terms of an energy-like function extremization, provided that the Markov property is not applied. The simulated height distributions are bimodal and right skewed, as in real community of plants. In the case of isolated plants, theoretical growth dynamics and speed correctly fit Arabidopsis thaliana experimental data reported in literature. Moreover, the growth dynamics of this model is shown to be consistent with the biomass production function of an independent model. These results suggest that memory effects play a non-negligible role in plant growth processes.

Induction of systemic resistance and management of safflower Macrophomina phaseolina root-rot disease by biocontrol agents

Three biocontrol agents such as Trichoderma harizianum, Pseudomonas fluorescens and Bacillus subtilis were isolated from safflower rhizosphere soil and tested individually for their effectiveness in controlling root-rot of safflower. Talc based formulations were prepared and treated the seeds at different concentrations for assessing their ability to induce plant growth and in turn control root-rot disease. Among bioagents, P. fluorescens and T. harzianum (10 g/kg) proved to be effective in controlling disease under laboratory, greenhouse and field conditions. The efficacy of these biocontrol agents are equivalent to the standard fungicide Bavistin (Carbedazim). Other than direct action of these biocontrol agents triggered defense related enzymes involved in phenyl proponoid pathways and phenols. Higher activity of peroxidase, phenylalanine ammonia-lyase, chitinase, polyphenol oxidase and β-1,3-glucanase was observed in P. fluorescens and T. harzianum treated safflower plants after challenge inoculation with M. phaseolina. Seed treatment with these biocontrol agents enhanced the seed germination and growth parameters against root-rot disease and they also induced systemic resistance and/or physiological changes leading to plant defense mechanisms.

Root Growth of Arabidopsis thaliana Is Regulated by Ethylene and Abscisic Acid Signaling Interaction in Response to HrpNEa, a Bacterial Protein of Harpin Group

HrpNEa is a harpin protein from Erwinia amylovora, a bacterial pathogen that causes fire blight in rosaceous plants. Treating plants with HrpNEa stimulates ethylene and abscisic acid (ABA) to induce plant growth and drought tolerance, respectively. Herein, we report that both growth hormones cooperate to mediate the role of HrpNEa in promoting root growth of Arabidopsis thaliana seedlings. Root growth is promoted coordinately with elevation in levels of ABA and ethylene subsequent to soaking of germinating seeds of wild-type (WT) Arabidopsis in a solution of HrpNEa. However, these responses are arrested by inhibiting WT roots from synthesizing ethylene as well as sensing of ABA and ethylene. The effects of HrpNEa on roots are also nullified in ethylene-insensitive etr1-1 and ein5-1 mutants and in the ABA-insensitive mutant abi2-1 of Arabidopsis. These results provide evidence for presence of a relationship between root growth enhancement and signaling by ABA and ethylene in response to HrpNEa. Nevertheless, when HrpNEa is applied to leaves, ethylene signaling is active in the absence of ABA signaling to promote plant growth. This suggests the presence of a different signaling mechanism in leaves from that in roots.

Causes and consequences of plant-associated biofilms

The rhizosphere is the critical interface between plant roots and soil where beneficial and harmful interactions between plants and microorganisms occur. Although microorganisms have historically been studied as planktonic (or free-swimming) cells, most are found attached to surfaces, in multicellular assemblies known as biofilms. When found in association with plants, certain bacteria such as plant growth promoting rhizobacteria not only induce plant growth but also protect plants from soil-borne pathogens in a process known as biocontrol. Contrastingly, other rhizobacteria in a biofilm matrix may cause pathogenesis in plants. Although research suggests that biofilm formation on plants is associated with biological control and pathogenic response, little is known about how plants regulate this association. Here, we assess the biological importance of biofilm association on plants.

Indolacetic and humic acids induce lateral root development through a concerted plasmalemma and tonoplast H+ pumps activation

Increasing evidences have indicated that humic substances can induce plant growth and productivity by functioning as an environmental source of auxinic activity. Here we comparatively evaluate the effects of indole-3-acetic acid (IAA) and humic acids (HA) isolated from two different soils (Inseptsol and Ultisol) and two different organic residues (vermicompost and sewage sludge) on root development and on activities of plasmalemma and tonoplast H(+ )pumps from maize roots. The data show that HA isolated from these different sources as well as low IAA concentrations (10(-10) and 10(-15) M) improve root growth through a markedly proliferation of lateral roots along with a differential activation not only of the plasmalemma but also of vacuolar H(+)-ATPases and H(+)-pyrophosphatase. Further, the vacuolar H(+)-ATPase had a peak of stimulation in a range from 10(-8) to 10(-10) M IAA, whereas the H(+)-pyrophosphatase was sensitive to a much broader range of IAA concentrations from 10(-3) to 10(-15) M. It is proposed a complementary view of the acid growth mechanism in which a concerted activation of the plasmalemma and tonoplast H(+ )pumps plays a key role in the root cell expansion process driven by environment-derived molecules endowed with auxinic activity, such as that of humic substances.

Fluorescent Pseudomonads associated with the rhizosphere of crops: an overview

Environmental concerns have led to the need of sustainable use of natural resources. The conventional agriculture caused considerable impacts on soils and waters. It is important to change certain agricultural managements to environmental cleaner techniques. The sustainable agriculture has pointed many approaches and techniques to reduce environmental impact. One of those strategies is the utilization of the soil microbiota to induce plant growth, control of plant diseases and biodegradation of xenobiotic compounds. Studies on the relationship between roots and microbiota are essential to achieve viable agricultural applications. These studies indicate that one of the most abundant microorganisms in the rhizosphere (area around the roots) is fluorescent Pseudomonas spp. They have been considered as an alternative to agrochemicals for controlling plant diseases and increasing plant development. This review addresses the main findings on fluorescent Pseudomonads. It summarizes and discusses significant aspects of this general topic, including (i) rhizosphere as a microhabitat; (ii) taxonomic, genetic and ecological aspects of fluorescent Pseudomonads in the rhizosphere; (iii) mechanisms of Plant Growth Promoting and Biological Control and (iv) commercial use of PGPR in agriculture.