Lipo-chitooligosaccharides Research Articles

Effect of rhizobial nod factors (lipo­chitooligosaccharide) on seedling growth of blackgram under salt stress

A study was carried out to examine the performance of blackgram seedlings under varying levels of salinity and to ascertain the remedial effect of lipo chitooligosaccharide (LCO) against salinity stress. Higher germination percentage, root and shoot length, vigour index and salt tolerance index and lower phytotoxicity of roots and shoots (0) were observed in control (no salinity) treatment irrespective of priming. Salinity negatively influenced the seedling growth and as the salinity increased the seedling growth characters were drastically reduced. The nod factor treated blackgram seedlings had relatively higher germination percentage , root and shoot length, vigour index and salt tolerance index and lower phytotoxicity of roots and shoots. Seed priming with nod factor was found to have significant effect on eliminating the effects of salinity.

Determining the Site of Action of Strigolactones during Nodulation.

Strigolactones (SLs) influence the ability of legumes to associate with nitrogen-fixing bacteria. In this study, we determine the precise stage at which SLs influence nodulation. We show that SLs promote infection thread formation, as a null SL-deficient pea (Pisum sativum) mutant forms significantly fewer infection threads than wild-type plants, and this reduction can be overcome by the application of the synthetic SL GR24. We found no evidence that SLs influence physical events in the plant before or after infection thread formation, since SL-deficient plants displayed a similar ability to induce root hair curling in response to rhizobia or Nod lipochitooligosaccharides (LCOs) and SL-deficient nodules appear to fix nitrogen at a similar rate to those of wild-type plants. In contrast, an SL receptor mutant displayed no decrease in infection thread formation or nodule number, suggesting that SL deficiency may influence the bacterial partner. We found that this influence of SL deficiency was not due to altered flavonoid exudation or the ability of root exudates to stimulate bacterial growth. The influence of SL deficiency on infection thread formation was accompanied by reduced expression of some early nodulation genes. Importantly, SL synthesis is down-regulated by mutations in genes of the Nod LCO signaling pathway, and this requires the downstream transcription factor NSP2 but not NIN This, together with the fact that the expression of certain SL biosynthesis genes can be elevated in response to rhizobia/Nod LCOs, suggests that Nod LCOs may induce SL biosynthesis. SLs appear to influence nodulation independently of ethylene action, as SL-deficient and ethylene-insensitive double mutant plants display essentially additive phenotypes, and we found no evidence that SLs influence ethylene synthesis or vice versa.

Underground communication – the new elements of signalling pathways of arbuscular mycorrhizal symbiosis

Abstract Mycorrhiza is a symbiotic relationship between living cells of the roots of higher plants and non-pathogenic fungi which inhabit soil and belong to Glomeromycota (endomycorrhizae) and Basidiomycota, Ascomycota (ectomycorrhizae). Although the phenomenon of mycorrhiza was discovered by a Polish botanist F.D. Kamieński already in 1881, various stages of establishing the symbiotic relationship between the partners are still not fully understood and explained. According to the current knowledge, the roots of host plants release strigolactones, which stimulate germination and branching of spores of arbuscular fungi. As a result, the fungi synthesize molecular signals, i.e. chitooligosaccharides (COs) and lipochitooligosaccharides (LCOS), called MycF factors. Thanks to the development of molecular biology techniques the probable cascade of events during the recognition of fungal MycF factor by the host-plant has been outlined. The enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase 1 (HMGR1) and also its product, mevalonic acid (MVA), play an essential role in the biosynthesis of sterols and isoprenoids in a plant cell. The recent studies indicate that these compounds may also play a very important role during establishing of the symbiotic mycorrhizal relationship. It is believed that MVA detects and transmits MycF factor to a cell nucleus of a host-plant triggering numerous necessary mechanisms in the plant cell to activate next steps of the mycorrhizal symbiosis. The discovery of HMGR1 and MVA sheds new light on symbiotic nature of mycorrhiza. This paper is a review of the current knowledge on the signal exchange during symbiotic interactions between mycorrhizal fungi and host plants. 1. Introduction. 2. Symbiotic nature of arbuscular fungi. 3. Arbuscular mycorrhiza in early stages. 4. Exchange of signaling molecules during arbuscular mycorrhiza formation. 5. Mevalonic acid – secondary signaling molecule messengers in the arbuscular mycorrhiza. 6. Protein kinase CCaMK as a key element in the establishment of arbuscular mycorrhiza. 7. Summary

Quantitative modelling of legume root nodule primordium induction by a diffusive signal of epidermal origin that inhibits auxin efflux.

BackgroundRhizobium nitrogen fixation in legumes takes place in specialized organs called root nodules. The initiation of these symbiotic organs has two important components. First, symbiotic rhizobium bacteria are recognized at the epidermis through specific bacterially secreted lipo-chitooligosaccharides (LCOs). Second, signaling processes culminate in the formation of a local auxin maximum marking the site of cell divisions. Both processes are spatially separated. This separation is most pronounced in legumes forming indeterminate nodules, such as model organism Medicago truncatula, in which the nodule primordium is formed from pericycle to most inner cortical cell layers.ResultsWe used computer simulations of a simplified root of a legume that can form indeterminate nodules. A diffusive signal that inhibits auxin transport is produced in the epidermis, the site of rhizobium contact. In our model, all cells have the same response characteristics to the diffusive signal. Nevertheless, we observed the fastest and strongest auxin accumulation in the pericycle and inner cortex. The location of these auxin maxima correlates with the first dividing cells of future nodule primordia in M. truncatula. The model also predicts a transient reduction of the vascular auxin concentration rootward of the induction site as is experimentally observed. We use our model to investigate how competition for the vascular auxin source could contribute to the regulation of nodule number and spacing.ConclusionOur simulations show that the diffusive signal may invoke the strongest auxin accumulation response in the inner root layers, although the signal itself is strongest close to its production site.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0935-9) contains supplementary material, which is available to authorized users.

Proteomic Studies on the Effects of Lipo-Chitooligosaccharide and Thuricin 17 under Unstressed and Salt Stressed Conditions in Arabidopsis thaliana.

Plants, being sessile organisms, are exposed to widely varying environmental conditions throughout their life cycle. Compatible plant-microbe interactions favor plant growth and development, and help plants deal with these environmental challenges. Microorganisms produce a diverse range of elicitor molecules to establish symbiotic relationships with the plants they associate with, in a given ecological niche. Lipo-chitooligosaccharide (LCO) and Thuricin 17 (Th17) are two such compounds shown to positively influence plant growth of both legumes and non-legumes. Arabidopsis thaliana responded positively to treatment with the bacterial signal compounds LCO and Th17 in the presence of salt stress (up to 250 mM NaCl). Shotgun proteomics of unstressed and 250 mM NaCl stressed A. thaliana rosettes (7 days post stress) in combination with the LCO and Th17 revealed many known, putative, hypothetical, and unknown proteins. Overall, carbon and energy metabolic pathways were affected under both unstressed and salt stressed conditions when treated with these signals. PEP carboxylase, Rubisco-oxygenase large subunit, pyruvate kinase, and proteins of photosystems I and II were some of the noteworthy proteins enhanced by the signals, along with other stress related proteins. These findings suggest that the proteome of A. thaliana rosettes is altered by the bacterial signals tested, and more so under salt stress, thereby imparting a positive effect on plant growth under high salt stress. The roles of the identified proteins are discussed here in relation to salt stress adaptation, which, when translated to field grown crops can be a crucial component and of significant importance in agriculture and global food production. The mass spectrometry proteomics data have been deposited to the ProteomeXchange with identifier PXD004742.

A Proteomic Approach to Lipo-Chitooligosaccharide and Thuricin 17 Effects on Soybean GerminationUnstressed and Salt Stress.

Salt stress is an important abiotic stressor affecting crop growth and productivity. Of the 20 percent of the terrestrial earth’s surface available as agricultural land, 50 percent is estimated by the United Nations Environment Program to be salinized to the level that crops growing on it will be salt-stressed. Increased soil salinity has profound effects on seed germination and germinating seedlings as they are frequently confronted with much higher salinities than vigorously growing plants, because germination usually occurs in surface soils, the site of greatest soluble salt accumulation. The growth of soybean exposed to 40 mM NaCl is negatively affected, while an exposure to 80 mM NaCl is often lethal. When treated with the bacterial signal compounds lipo-chitooligosaccharide (LCO) and thuricin 17 (Th17), soybean seeds (variety Absolute RR) responded positively at salt stress of up to 150 mM NaCl. Shotgun proteomics of unstressed and 100 mM NaCl stressed seeds (48 h) in combination with the LCO and Th17 revealed many known, predicted, hypothetical and unknown proteins. In all, carbon, nitrogen and energy metabolic pathways were affected under both unstressed and salt stressed conditions when treated with signals. PEP carboxylase, Rubisco oxygenase large subunit, pyruvate kinase, and isocitrate lyase were some of the noteworthy proteins enhanced by the signals, along with antioxidant glutathione-S-transferase and other stress related proteins. These findings suggest that the germinating seeds alter their proteome based on bacterial signals and on stress, the specificity of this response plays a crucial role in organ maturation and transition from one stage to another in the plants' life cycle; understanding this response is of fundamental importance in agriculture and, as a result, global food security. The mass spectrometry proteomics data have been deposited to the ProteomeXchange with identifier PXD004106.

Intraradical colonization by arbuscular mycorrhizal fungi triggers induction of a lipochitooligosaccharide receptor.

Functional divergence of paralogs following gene duplication is one of the mechanisms leading to evolution of novel pathways and traits. Here we show that divergence of Lys11 and Nfr5 LysM receptor kinase paralogs of Lotus japonicus has affected their specificity for lipochitooligosaccharides (LCOs) decorations, while the innate capacity to recognize and induce a downstream signalling after perception of rhizobial LCOs (Nod factors) was maintained. Regardless of this conserved ability, Lys11 was found neither expressed, nor essential during nitrogen-fixing symbiosis, providing an explanation for the determinant role of Nfr5 gene during Lotus-rhizobia interaction. Lys11 was expressed in root cortex cells associated with intraradical colonizing arbuscular mycorrhizal fungi. Detailed analyses of lys11 single and nfr1nfr5lys11 triple mutants revealed a functional arbuscular mycorrhizal symbiosis, indicating that Lys11 alone, or its possible shared function with the Nod factor receptors is not essential for the presymbiotic phases of AM symbiosis. Hence, both subfunctionalization and specialization appear to have shaped the function of these paralogs where Lys11 acts as an AM-inducible gene, possibly to fine-tune later stages of this interaction.

Effect of Lipo-chitooligosaccharides on seed germination, growth, vigour and biochemical changes in soybean seedling

SUMMARY The bacterium-to-plant signal, lipo-chitooligosaccharides (LCOs) or Nod factor induces cell division and enhances seed germination. The experiment was conducted to test the efficacy of LCO on soybean seed germination and seedling growth under room temperature by roll towel method. Different concentrations of LCO were used for seed treatment along with microbial inoculum and biocontrol agents as a control. Among the treatments, concentration of LCO @ 1.8 and 3.6 ml/kg of seed performed better compared to other treatments. The results revealed that treating with LCO could influence soybean seed germination and growth of seedlings.

Molecular basis of lipo-chitooligosaccharide recognition by the lysin motif receptor-like kinase LYR3in legumes.

LYR3 [LysM (lysin motif) receptor-like kinase 3] of Medicago truncatula is a high-affinity binding protein for symbiotic LCO (lipo-chitooligosaccharide) signals, produced by rhizobia bacteria and arbuscular mycorrhizal fungi. The present study shows that LYR3 from several other legumes, but not from two Lupinus species which are incapable of forming the mycorrhizal symbiosis, bind LCOs with high affinity and discriminate them from COs (chitooligosaccharides). The biodiversity of these proteins and the lack of binding to the Lupinus proteins were used to identify features required for high-affinity LCO binding. Swapping experiments between each of the three LysMs of the extracellular domain of the M. truncatula and Lupinus angustifolius LYR3 proteins revealed the crucial role of the third LysM in LCO binding. Site-directed mutagenesis identified a tyrosine residue, highly conserved in all LYR3 LCO-binding proteins, which is essential for high-affinity binding. Molecular modelling suggests that it may be part of a hydrophobic tunnel able to accommodate the LCO acyl chain. The lack of conservation of these features in the binding site of plant LysM proteins binding COs provides a mechanistic explanation of how LCO recognition might differ from CO perception by structurally related LysM receptors.

Characterizing Genotype × Management Interactions on Soybean Seed Yield

Increased soybean [Glycine max (L.) Merr.] commodity prices in recent years have generated interest in high‐input systems to increase yield. The objective of this study was to evaluate the effects of current, high‐yielding cultivars under high‐ and low‐input systems on soybean yield and yield components. Research trials were conducted at 19 locations spanning nine states from 2012 to 2014. At each location, six high‐yielding cultivars were grown under three input systems: (i) standard practice (SP, current recommended practices), (ii) high‐input treatment consisting of a seed treatment fungicide, insecticide, nematistat, inoculant, and lipo‐chitooligosaccharide (LCO); soil‐applied N fertilizer; foliar LCO, fertilizer, antioxidant, fungicide and insecticide (SOYA), and (iii) SOYA minus foliar fungicide (SOYA‐FF). An individual site‐year yield analysis found only 3 of 53 (5.7%) site‐years examined had a significant cultivar × input system interaction, suggesting cultivar selection and input system decisions can remain independent. Across all site‐years, the SOYA and SOYA‐FF treatments yielded 231 (5.5%) and 147 kg ha–1 (3.5%) more than the SP, and input system differences were found among maturity groups. Yield component measurements (seeds m–2, seed mass, early‐season and final plant stand, pods plant–1, and seeds pod–1) indicated positive yield responses were due to increased seeds m–2 and seed mass. While both high‐input systems increased yield on average, grower return on investment (ROI) would be negative given today's commodity prices. These results further support the use of integrated pest management principles for making input decisions instead of using prophylactic applications to maximize soybean yield and profitability.

Pre-announcement of symbiotic guests: transcriptional reprogramming by mycorrhizal lipochitooligosaccharides shows a strict co-dependency on the GRAS transcription factors NSP1 and RAM1.

BackgroundMore than 80 % of all terrestrial plant species establish an arbuscular mycorrhiza (AM) symbiosis with Glomeromycota fungi. This plant-microbe interaction primarily improves phosphate uptake, but also supports nitrogen, mineral, and water aquisition. During the pre-contact stage, the AM symbiosis is controled by an exchange of diffusible factors from either partner. Amongst others, fungal signals were identified as a mix of sulfated and non-sulfated lipochitooligosaccharides (LCOs), being structurally related to rhizobial nodulation (Nod)-factor LCOs that in legumes induce the formation of nitrogen-fixing root nodules. LCO signals are transduced via a common symbiotic signaling pathway (CSSP) that activates a group of GRAS transcription factors (TFs). Using complex gene expression fingerprints as molecular phenotypes, this study primarily intended to shed light on the importance of the GRAS TFs NSP1 and RAM1 for LCO-activated gene expression during pre-symbiotic signaling.ResultsWe investigated the genome-wide transcriptional responses in 5 days old primary roots of the Medicago truncatula wild type and four symbiotic mutants to a 6 h challenge with LCO signals supplied at 10-7/-8 M. We were able to show that during the pre-symbiotic stage, sulfated Myc-, non-sulfated Myc-, and Nod-LCO-activated gene expression almost exclusively depends on the LysM receptor kinase NFP and is largely controled by the CSSP, although responses independent of this pathway exist. Our results show that downstream of the CSSP, gene expression activation by Myc-LCOs supplied at 10-7/-8 M strictly required both the GRAS transcription factors RAM1 and NSP1, whereas those genes either co- or specifically activated by Nod-LCOs displayed a preferential NSP1-dependency. RAM1, a central regulator of root colonization by AM fungi, controled genes activated by non-sulfated Myc-LCOs during the pre-symbiotic stage that are also up-regulated in areas with early physical contact, e.g. hyphopodia and infecting hyphae; linking responses to externally applied LCOs with early root colonization.ConclusionsSince both RAM1 and NSP1 were essential for the pre-symbiotic transcriptional reprogramming by Myc-LCOs, we propose that downstream of the CSSP, these GRAS transcription factors act synergistically in the transduction of those diffusible signals that pre-announce the presence of symbiotic fungi.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-2224-7) contains supplementary material, which is available to authorized users.

The strigolactone biosynthesis gene DWARF27 is co-opted in rhizobium symbiosis

BackgroundStrigolactones are a class of plant hormones whose biosynthesis is activated in response to phosphate starvation. This involves several enzymes, including the carotenoid cleavage dioxygenases 7 (CCD7) and CCD8 and the carotenoid isomerase DWARF27 (D27). D27 expression is known to be responsive to phosphate starvation. In Medicago truncatula and rice (Oryza sativa) this transcriptional response requires the GRAS-type proteins NSP1 and NSP2; both proteins are essential for rhizobium induced root nodule formation in legumes. In line with this, we questioned whether MtNSP1-MtNSP2 dependent MtD27 regulation is co-opted in rhizobium symbiosis.ResultsWe provide evidence that MtD27 is involved in strigolactone biosynthesis in M. truncatula roots upon phosphate stress. Spatiotemporal expression studies revealed that this gene is also highly expressed in nodule primordia and subsequently becomes restricted to the meristem and distal infection zone of a mature nodules. A similar expression pattern was found for MtCCD7 and MtCCD8. Rhizobium lipo-chitooligosaccharide (LCO) application experiments revealed that of these genes MtD27 is most responsive in an MtNSP1 and MtNSP2 dependent manner. Symbiotic expression of MtD27 requires components of the symbiosis signaling pathway; including MtDMI1, MtDMI2, MtDMI3/MtCCaMK and in part MtERN1. This in contrast to MtD27 expression upon phosphate starvation, which only requires MtNSP1 and MtNSP2.ConclusionOur data show that the phosphate-starvation responsive strigolactone biosynthesis gene MtD27 is also rapidly induced by rhizobium LCO signals in an MtNSP1 and MtNSP2-dependent manner. Additionally, we show that MtD27 is co-expressed with MtCCD7 and MtCCD8 in nodule primordia and in the infection zone of mature nodules.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0651-x) contains supplementary material, which is available to authorized users.

Inter-organismal signaling and management of the phytomicrobiome.

The organisms of the phytomicrobiome use signal compounds to regulate aspects of each other’s behavior. Legumes use signals (flavonoids) to regulate rhizobial nod gene expression during establishment of the legume-rhizobia N2-fixation symbiosis. Lipochitooligosaccharides (LCOs) produced by rhizobia act as return signals to the host plant and are recognized by specific lysine motif receptor like kinases, which triggers a signal cascade leading to nodulation of legume roots. LCOs also enhance plant growth, particularly when plants are stressed. Chitooligosaccharides activate plant immune responses, providing enhanced resistance against diseases. Co-inoculation of rhizobia with other plant growth promoting rhizobacteria (PGPR) can improve nodulation and crop growth. PGPR also alleviate plant stress by secreting signal compounds including phytohormones and antibiotics. Thuricin 17, a small bacteriocin produced by a phytomicrobiome member promotes plant growth. Lumichrome synthesized by soil rhizobacteria function as stress-sensing cues. Inter-organismal signaling can be used to manage/engineer the phytomicrobiome to enhance crop productivity, particularly in the face of stress. Stressful conditions are likely to become more frequent and more severe because of climate change.

The response of canola cultivars to lipo-chitooligosaccharide (Nod Bj V [C18:1, MeFuc]) and thuricin 17

Lipo-chitooligosaccharides (LCOs) are signal molecules that play a role in initiating the symbiotic legume-rhizobia and arbuscular mycorrhizal processes. Thuricin 17 is a bacteriocin produced by Bacillus thuringiensis strain NEB 17. Previous work has shown that the application of a 10−6 M LCO solution, or a 10−11 M thuricin 17 solution, can stimulate the germination and growth of a wide range of plants. The objectives were: to grow canola cultivar 04C111 under optimal temperature conditions in a greenhouse, and to assess the effect of LCO seed application and spray treatment on 04C111 floral initiation, architecture, and factors that contribute to yield; to assess the effect of a thuricin 17 seed application treatment upon factors that contribute to 04C111 yield in a stressfully high temperature greenhouse system; and to assess the effect of an LCO seed application and spray treatment on Topas floral initiation, architecture, and factors that contribute to yield, and seed quality, in a simulated “cool spring” greenhouse system. According to the 95 % confidence limits, Brassica napus cultivars grown from untreated seed produced 39 % fewer to 1 % fewer branches than plants grown from LCO-treated seed. Application of an LCO foliar spray increased the total of branch lengths per 04C111 plant by 16.93 ± 8.41 cm. Based on the stem-to-branch length ratio, LCO-sprayed 04C111 plants were 68 % less apically dominant than unsprayed plants. Topas plants that were sprayed with LCO produced seed with approximately 4.45 ± 0.23 % more oil (% d.w.) than unsprayed plants. For both cultivars, seed treatment with 10−6 M of LCO produced plants with a higher average sum of primary, secondary, and tertiary branch (≥1 cm) frequencies.

Effect of lipo-chitooligosaccharide on early growth of C4 grass seedlings.

Although lipo-chitooligosaccharides (LCOs) are important signal molecules for plant-symbiont interactions, a number of reports suggest that LCOs can directly impact plant growth and development, separate from any role in plant symbioses. In order to investigate this more closely, maize and Setaria seedlings were treated with LCO and their growth was evaluated. The data indicate that LCO treatment significantly enhanced root growth. RNA-seq transcriptomic analysis of LCO-treated maize roots identified a number of genes whose expression was significantly affected by the treatment. Among these genes, some LCO-up-regulated genes are likely involved in root growth promotion. Interestingly, some stress-related genes were down-regulated after LCO treatment, which might indicate reallocation of resources from defense responses to plant growth. The promoter activity of several LCO-up-regulated genes using a β-glucuronidase reporter system was further analysed. The results showed that the promoters were activated by LCO treatment. The data indicate that LCO can directly impact maize root growth and gene expression.

Lipochitooligosaccharides modulate plant host immunity to enable endosymbioses.

Symbiotic nitrogen-fixing rhizobium bacteria and arbuscular mycorrhizal fungi use lipochitooligosaccharide (LCO) signals to communicate with potential host plants. Upon a compatible match, an intimate relation is established during which the microsymbiont is allowed to enter root (-derived) cells. Plants perceive microbial LCO molecules by specific LysM-domain-containing receptor-like kinases. These do not only activate a common symbiosis signaling pathway that is shared in both symbioses but also modulate innate immune responses. Recent studies revealed that symbiotic LCO receptors are closely related to chitin innate immune receptors, and some of these receptors even function in symbiosis as well as immunity. This raises questions about how plants manage to translate structurally very similar microbial signals into different outputs. Here, we describe the current view on chitin and LCO perception in innate immunity and endosymbiosis and question how LCOs might modulate the immune system. Furthermore, we discuss what it takes to become an endosymbiont.

Supplementation with solutions of lipo-chitooligosacharide Nod Bj V (C18:1, MeFuc) and thuricin 17 regulates leaf arrangement, biomass, and root development of canola (Brassica napus [L.

Recent work has shown that plant-to-microbe signals can enhance the growth of a wide range of crops. Nevertheless, canola (Brassica napus L.), which forms neither arbuscular mycorrhizal nor nitrogen-fixing symbioses, has not been rigorously evaluated for its capacity to perceive and respond to microbe-to-plant signals. It was shown previously that the Bradyrhizobium japonicum lipo-chitooligosaccharide (LCO) and Bacillus thuringiensis bacteriocin thuricin 17 enhance the germination and growth of other crop species. To evaluate canola’s response, B. napus plants were grown in controlled environment chambers, in either peat pellets or large plant culture vessels. In the peat pellet system, plants that were irrigated with 10−6 M LCO, and grown at 30 °C, produced one more leaf than water- or signal-treated plants that were grown at 25/20 °C. The numbers of cotyledons (seed leaves) produced by thuricin 17-treated plants was greater than LCO treated plants and the control treatment. Among the plants grown in vessels, those grown with 0.2 M NaCl and 10−9 M thuricin 17 were taller than either treated or untreated plants that were grown with 10−5 M NaCl. Under 10/4 °C and 4 × 10−5 M NaCl conditions, only seeds treated with thuricin 17 produced roots. Among the plants grown in vessels at 30/30 °C, those treated with 10−11 M thuricin 17 resulted in approximately one more leaf per plant than nM. Root lengths were shortened with 10−5 M NaCl and 10−9 M thuricin 17, compared to lower salinities. At 30/30 °C, plants grown with 10−5 M NaCl and 10−9 M thuricin 17 were heavier than plants grown in nonsaline media without thuricin 17. Where LCO supplementation may stimulate a competitive form, thuricin 17 supplementation triggers a reduction in the plant’s surface area, which may reduce the plant’s vulnerability to prohibitive salinity levels.

Rhizobium Lipo-chitooligosaccharide Signaling Triggers Accumulation of Cytokinins in Medicago truncatula Roots

Legume rhizobium symbiosis is initiated upon perception of bacterial secreted lipo-chitooligosaccharides (LCOs). Perception of these signals by the plant initiates a signaling cascade that leads to nodule formation. Several studies have implicated a function for cytokinin in this process. However, whether cytokinin accumulation and subsequent signaling are an integral part of rhizobium LCO signaling remains elusive. Here, we show that cytokinin signaling is required for the majority of transcriptional changes induced by rhizobium LCOs. In addition, we demonstrate that several cytokinins accumulate in the root susceptible zone 3 h after rhizobium LCO application, including the biologically most active cytokinins, trans-zeatin and isopentenyl adenine. These responses are dependent on calcium- and calmodulin-dependent protein kinase (CCaMK), a key protein in rhizobial LCO-induced signaling. Analysis of the ethylene-insensitive Mtein2/Mtsickle mutant showed that LCO-induced cytokinin accumulation is negatively regulated by ethylene. Together with transcriptional induction of ethylene biosynthesis genes, it suggests a feedback loop negatively regulating LCO signaling and subsequent cytokinin accumulation. We argue that cytokinin accumulation is a key step in the pathway leading to nodule organogenesis and that this is tightly controlled by feedback loops.

Activation of symbiosis signaling by arbuscular mycorrhizal fungi in legumes and rice.

Establishment of arbuscular mycorrhizal interactions involves plant recognition of diffusible signals from the fungus, including lipochitooligosaccharides (LCOs) and chitooligosaccharides (COs). Nitrogen-fixing rhizobial bacteria that associate with leguminous plants also signal to their hosts via LCOs, the so-called Nod factors. Here, we have assessed the induction of symbiotic signaling by the arbuscular mycorrhizal (Myc) fungal-produced LCOs and COs in legumes and rice (Oryza sativa). We show that Myc-LCOs and tetra-acetyl chitotetraose (CO4) activate the common symbiosis signaling pathway, with resultant calcium oscillations in root epidermal cells of Medicago truncatula and Lotus japonicus. The nature of the calcium oscillations is similar for LCOs produced by rhizobial bacteria and by mycorrhizal fungi; however, Myc-LCOs activate distinct gene expression. Calcium oscillations were activated in rice atrichoblasts by CO4, but not the Myc-LCOs, whereas a mix of CO4 and Myc-LCOs activated calcium oscillations in rice trichoblasts. In contrast, stimulation of lateral root emergence occurred following treatment with Myc-LCOs, but not CO4, in M. truncatula, whereas both Myc-LCOs and CO4 were active in rice. Our work indicates that legumes and non-legumes differ in their perception of Myc-LCO and CO signals, suggesting that different plant species respond to different components in the mix of signals produced by arbuscular mycorrhizal fungi.

Impact of Lipo-Chito-Oligosaccharides (LCO) as Foliar Spray on Soybean (Glycine max (L.) Merr.) Yield

The bacterium to plant signal, lipo-chito-oligosaccharides (LCOs) or Nod factors induce cell division and enhance plant growth. In the present study LCO has been applied through foliar spray at two different stages (V 2 ), 20-25 DAS and 40-45 DAS (V 4 ). All the yield contributing parameters were increased by the foliar spray of LCO in soybean and the maximum yield was recorded in LCO @ 300 ml ha -1 at 20-25 DAS. The yield increased by 10.6 per cent at kharif and 14.3 per cent during rabi 2012. Correlation studies indicated that seed yield per hectare exhibited stable positive association vis-a vis number of flowers, pods per plant, fertility co- efficient, 100 grains weight and harvest index at different stages and seasons