Efficacy of biological preparations of soybean root nodule bacteria modified with a homologous lectin

The effect of various biopreparations of the root nodule bacterium Bradyrhizobium japonicum, modified with a homologous lectin, on the virulence of Rhizobia, the nitrogen-fixing activity of root nodules, and the productivity of the soybean (Glycine max (L.) Merr.) was studied. It was shown that a homologous lectin, added to a bacterial suspension when manufacturing biopreparations on a liquid and solid support, increases the efficiency of the soybean symbiotic system and the productivity of the host plant. The potentialities of using bacterial preparations modified with a homologous lectin are discussed.     

Productivity of soybean-rhizobium symbiosis after modification of root nodule bacteria activity with exogenous proteins

Plant growth experiments were conducted to assess symbiotic efficiency, photosynthetic rates, and the development of soybean (Glycine max (L.) Merrill) seedlings after seed inoculation with active and inactive strains of root nodule bacteria Bradyrhizobium japonicum preincubated in the presence homologous and heterologous proteins. The properties of active and inactive symbiotic strains were differentially modulated by homologous soybean lectin, which had a marked influence on plant physiological condition. The incubation of active rhizobia with a homologous lectin, i.e., lectin of the respective plant, increased the nitrogen-fixing activity of nodules and, consequently, elevated photosynthetic rates and weight increments in soybean plants. At the same time, the homologous lectin suppressed the symbiotic properties of inactive strain of nodule bacteria. The preincubation of rhizobia with a heterologous pea lectin had virtually no effect on functioning of symbiotic apparatus and photosynthetic rate, whereas the preincubation of root nodule bacteria with human albumin exerted an effect similar to that induced by a homologous lectin on symbiotic productivity.     

Immunochemical properties and localization of lectin from the basidiomycete <Emphasis Type="Italic">Grifola frondosa</Emphasis> (Fr.) S.F. Gray

The complex of immunochemical methods was applied to study the ability of the lectin from the fungus Grifola frondosa (Fr.) S.F. Gray to interact with homologous and non-homologous rabbit and human polyclonal antibodies. The results of immunodot assay with the fragments of proteolytically cleaved antibodies demonstrated the binding of the lectin only with the Fab fragments (antigen-binding center) of homologous antibodies, which is evidence of specific “antigen-antibody” interaction. The revealed interaction of the lectin with non-homologous antibodies (rabbit antibodies to bacterial O-antigens and the commercial preparation of human g-globulin) is most likely accomplished due to the contact of the carbohydrate-binding region of the lectin with the carbohydrate moiety of the antibodies (“lectin-carbohydrate”). Immunofluorescence microscopy with homologous antibodies revealed that lectin was diffusely and unevenly distributed over the surface of the hyphae, forming agglomerates in the region of buckles and young shoots.     

Response and interaction of <Emphasis Type="Italic">Bradyrhizobium japonicum</Emphasis> and arbuscular mycorrhizal fungi in the soybean rhizosphere

Regulatory response and interaction of Bradyrhizobium and arbuscular mycorrhizal fungi (AMF) play a vital role in rhizospheric soil processes and productivity of soybean (Glycine max L.). Nitrogen (N) and phosphorus (P) are essential nutrients for plant growth and productivity, the synergistic interaction(s) of AMF and Bradyrhizobium along with rhizospheric beneficial microorganisms stimulate soybean growth and development through enhanced mineral nutrient acquisition (N and P) and improved rhizosphere environment. Such interactions are crucial, especially under low-input eco-friendly agricultural cropping systems, which rely on biological processes rather than agrochemicals to maintain soil quality, sustainability, and productivity. Furthermore, enhancement of N-fixation by root nodules along with AMF-mediated synergism improves plant P nutrition and uptake, and proliferation of phosphate-solubilizing fungi. However, the genetic and/or allelic diversity among native strains, their genes/enzymes and many environmental factors (e.g., soil organic matter, fertilizers, light, temperature, soil moisture, and biotic interactors) affect the interactions between AMF and Bradyrhizobium. New information is available regarding the genetic composition of elite soybean inoculant strains in maximizing symbiotic performance, N-fixing capabilities and depending on N and P status the host-mediated regulation of root architecture. Overall, for sustainable soybean production systems, a deeper understanding of the interaction effects of Bradyrhizobium and AMF co-inoculation are expected in the future, so that optimized combinations of microorganisms can be applied as effective soil inoculants for plant growth promotion and fitness. The objective of this review is to offer insights into the mechanistic interactions of AMF and Bradyrhizobium and rhizopheric soil health, and elucidate the role of environmental factors in regulating growth, development and sustainable soybean productivity.     

Cloning <Emphasis Type="Italic">PIP</Emphasis> genes in drought-tolerant vetiver grass and responses of transgenic <Emphasis Type="Italic">VzPIP2;1</Emphasis> soybean plants to water stress

Vetiver grass [Vetiveria zizanioides (L.) Nash] displays comprehensive abiotic stress tolerance closely related to fine maintenance of plant water relation mediated by plasma membrane intrinsic proteins (PIPs). Two open reading frame sequences of PIPs (867 and 873 bp) were cloned from vetiver grass and named as VzPIP1;1 and VzPIP2;1, respectively. Expression of green fluorescent protein revealed only subcellular localization of VzPIP2;1 in the plasma membrane. Agrobacterium tumefaciens mediated transgenic (VzPIP2;1) soybean plants had a higher water content in above-ground parts under sufficient water supply through enhancing transpiration as compared to the non-transgenic plants but displayed a more severe drought injury because of a lower photosynthesis and a higher transpiration rate. However, A. rhizogenes mediated transgenic soybean plants kept a higher water content in above-ground parts by improving root water transport and kept a more effective photosynthesis under normal and drought conditions.     

Cell culture system versus adventitious root culture system in Asian and American ginseng: a collation

Panax ginseng and Panax quinquefolius of Panax genus are valuable as health foods as well as pharmaceuticals for the treatment of cancer, diabetes and ageing as these plants possess saponins. In the current study, Cell and adventitious root cultures of P. ginseng and P. quinquefolius were investigated for the biomass, cell division, saponin content and ginsenosides profile from four lines namely P. quinquefolius (AM), P. ginseng mountain (Mt.) Baekdu line, P. ginseng Cheong-sol line (CS) and P. ginseng CBN line (CBN) with the objective of comparing cell and adventitious root systems to check their efficacy for the production of ginseng saponins. Additionally, genes related to ginsenoside biosynthesis were also analyzed concerning to cell and adventitious root lines. The results indicated that various cell lines were better in multiplication and growth compared to adventitious root lines. However, adventitious root lines showed higher accumulation of dry biomass (1.5–2 fold) than that of cell lines. CS adventitious root line showed higher saponin content and ginsenoside productivity (10.48 mg·g^?1 DW, 12.88 mg·L^?1, respectively) than that of CS cell line (9.50 mg·g^?1 DW, 2.39 mg·L^?1, respectively). Especially, Rd ginsenoside productivity of CS adventitious root line recorded fourfold higher than CS cell line. Genes which are related to ginsenoside biosynthesis such as P. ginseng squalene synthase (PgSS2), P. ginseng squalene epoxidase (PgSE2), P. ginseng protopanaxadial synthase (PgPPDS) and P. ginseng protopanaxatriol synthase (PgPPTS) were analyzed by real time quantitative polymerase chain reaction to support ginsenoside production. The adventitious root culture system described in this study is useful system for biomass and ginsenoside production.     

Isolation and identification of cultivated bacteria associated with soybeans and their biocontrol activity against <Emphasis Type="Italic">Phytophthora sojae</Emphasis>

One hundred bacteria, isolated from rhizospheric soil and rhizoplane of healthy soybean plants, were assayed for antifungal activity against six Phytophthora sojae isolates. Nine of the tested bacteria inhibited the hyphal growth of P. sojae in vitro. They were subsequently evaluated for their in vitro traits and identified using the 16S rRNA gene sequences. Four of them (Paenibacillus sp.,—S1; Streptomyces sp.,—S9, S10 and S11) were further selected on the basis of their strongest antagonistic activity in vitro against P. sojae race 4, the predominant race in most growing soybean areas in Canada, and tested for their beneficial effects on soybean plants in the greenhouse. Results showed that application of bacterial strain S11 as seed coating reduced the disease severity by 57.1% and increased the root and shoot weight by and 140 and 108% respectively, in comparison to the diseased control. Overall, a positive correlation was recorded between the in vitro and in planta effects of the selected bacteria. This is promising for further application as select environmentally safe biological control agents in the protection of soybean against root rot diseases.     

Acid phosphatase gene <Emphasis Type="Italic">GmHAD1</Emphasis> linked to low phosphorus tolerance in soybean,through fine mapping

Key message

Map-based cloning identified GmHAD1, a gene which encodes a HAD-like acid phosphatase, associated with soybean tolerance to low phosphorus stress.

Abstract

Phosphorus (P) deficiency in soils is a major limiting factor for crop growth worldwide. Plants may adapt to low phosphorus (LP) conditions via changes to root morphology, including the number, length, orientation, and branching of the principal root classes. To elucidate the genetic mechanisms for LP tolerance in soybean, quantitative trait loci (QTL) related to root morphology responses to LP were identified via hydroponic experiments. In total, we identified 14 major loci associated with these traits in a RIL population. The log-likelihood scores ranged from 2.81 to 7.43, explaining 4.23–13.98% of phenotypic variance. A major locus on chromosome 08, named qP8-2, was co-localized with an important P efficiency QTL (qPE8), containing phosphatase genes GmACP1 and GmACP2. Another major locus on chromosome 10 named qP10-2 explained 4.80–13.98% of the total phenotypic variance in root morphology. The qP10-2 contains GmHAD1, a gene which encodes an acid phosphatase. In the transgenic soybean hairy roots, GmHAD1 overexpression increased P efficiency by 8.4–16.5% relative to the control. Transgenic Arabidopsis plants had higher biomass than wild-type plants across both short- and long-term P reduction. These results suggest that GmHAD1, an acid phosphatase gene, improved the utilization of organic phosphate by soybean and Arabidopsis plants.

     

Characterization of S-adenosylmethionine synthetases in soybean under flooding and drought stresses

Soybean is stress-sensitive crop that exhibits markedly reduced growth under flooding and drought conditions. Three S-adenosylmethionine synthetases (SAMs) proteins were identified as flooding and drought responsive proteins in soybean using a proteomic technique. To better understand the role of these SAMs proteins in soybean under flooding and drought stresses, temporal, organ, and stress specificities were examined at mRNA and enzyme activity levels. The activity of SAMs decreased in response to the flooding, however, it was not significantly changed by NaCl, cold, gibberellic acid, and calcium in soybean roots. The activity of SAMs was induced in roots and hypocotyls under drought. The mRNA expression of the S-adenosylmethionine synthetase (SAMs) family was down-regulated in root tips and roots under the flooding and the drought, and SAMs 1 and SAMs 2 were down-regulated in roots under both stresses. A gene 1-aminocyclopropane-1-carboxylate synthase was up-regulated in root tips, roots, and hypocotyls under drought, however, it was not changed in root tips and roots under the flooding. In addition, 1-aminocyclopropane-1-carboxylate oxidase was induced in root tips under flooding and drought. These results suggest that SAMs was involved in the response to the flooding and drought and it might affect ethylene biosynthesis in soybean.     

<Emphasis Type="Italic">GmDim1</Emphasis> Gene Encodes Nucleolar Localized U5-Small Nuclear Ribonucleoprotein in <Emphasis Type="Italic">Glycine max</Emphasis>

The dim1⁺ gene family is essential for G2/M transition during mitosis and encodes a small nuclear ribonucleoprotein that functions in the mRNA splicing machinery of eukaryotes. However, the plant homolog of DIM1 gene has not been defined yet. Here, we identified a gene named GmDim1 positioned on chromosome 9 of soybean (Glycine max (L.) Merr.) with 80% homology to other eukaryotic dim1⁺ family genes. A domain of soybean DIM1 protein was primarily conserved with U5 snRNP protein family and secondarily aligned with mitotic DIM1 protein family. The GmDim1 gene was expressed constitutively in all soybean organs. The transgenic Arabidopsis thaliana (L.) plants overexpressing GmDim1 showed early flowering and stem elongation, produced multiple shoots and continued flowering after the post-flowering stage. DIM1 proteins transiently expressed in onion cells were localized in the nucleus with dense deposition in the nucleolus. Therefore, we propose that the soybean GmDim1 gene is a component of plant U5 snRNP involved in mRNA splicing and normal progress of plant growth.     

Poly-γ-glutamic acid productivity of <Emphasis Type="Italic">Bacillus subtilis</Emphasis> BsE1 has positive function in motility and biocontrol against <Emphasis Type="Italic">Fusarium graminearum</Emphasis>

In this study, we investigate the relationship between γ-PGA productivity and biocontrol capacity of Bacillus subtilis BsE1; one bacterial isolate displayed 62.14% biocontrol efficacy against Fusarium root rot. The γ-PGA yield assay, motility assay, wheat root colonization assay, and biological control assay were analysed in different γ-PGA yield mutants of BsE1. The pgsB (PGA-synthase-CapB gene) deleted mutant of BsE1 reduced γ-PGA yield and exhibited apparent decline of in vitro motile ability. Deletion of pgsB impaired colonizing capacity of BsE1 on wheat root in 30 days, also lowered biocontrol efficacies from 62.08% (wild type BsE1) to 14.22% in greenhouse experiment against Fusarium root rot. The knockout of pgdS and ggt (genes relate to two γ-PGA degrading enzymes) on BsE1, leads to a considerable improvement in polymer yield and biocontrol efficacy, which attains higher level compared with wild type BsE1. Compared with ΔpgsB mutant, defense genes related to reactive oxygen species (ROS) and phytoalexin expressed changes by notable levels on wheat roots treated with BsE1, demonstrating the functional role γ-PGA plays in biocontrol against Fusarium root rot. γ-PGA is not only important to the motile and plant root colonization ability of BsE1, but also essential to the biological control performed by BsE1 against Fusarium root rot. Our goal in this study is to reveals a new perspective of BCAs screening on bacterial isolates, without good performance during pre-assays of antagonism ability.     

Mannan-binding lectins in the coelomic fluid of various species of Far Eastern echinoderms

A mannan-binding lectin activity was revealed in the coelomic fluid of the following echinoderm species inhabiting the coastal areas of the Sea of Japan, the holothurian Eupentacta fraudatrio, sea urchins Echinocardium cordatum, Strongylocentrotus nudus and S. intermedius, brittle star Amphipholis kochii, sea stars Asterina pectinifera, Lethasterias fusca, Lysastrosoma anthosticta, and Distolasterias nipon. It was shown that, concurrently with the general pattern of lectin interaction with branched bacterial mannans, there were also distinctions caused by the fine carbohydrate specificity of lectins. The obtained data preconditioned the further study of physical and chemical properties and structural features of the echinoderm MBL and the revelation of their role in the formation of the adaptive immune response and in other biological processes.     

Characterization of chickpea (<Emphasis Type="Italic">Cicer arietinum</Emphasis> L.) lectin for biological activity

Lectins are proteins that are subject of intense investigations. Information on lectin from chickpea (Cicer arietinum L.) with respect to its biological activities are very limited. In this study, we purified lectin from the seeds of chickpea employing DEAE-cellulose and SP-Sephadex ion exchange chromatography and identified its molecular subunit mass as 35 kDa. The free radical scavenging activity of lectin measured by the DPPH assay has IC₅₀ of 0.88 µg/mL. Lectin exerted antifungal activity against Candida krusei, Fusarium oxysporium oxysporium, Saccharomyces cerevisiae and Candida albicans, while antibacterial activity against E. coli, B. subtilis, S. marcescens and P. aeruginosa. The minimum inhibitory concentrations were 200, 240, 160 and 140 µg for C. krusei, F. oxysporium, S. cerevisiae and C. albicans respectively. Lectin was further examined for its antiproliferative potential against cancerous cell line. The cell viability assay indicated a high inhibition activity on Ishikawa, HepG2, MCF-7 and MDA-MB-231 with IC₅₀ value of 46.67, 44.20, 53.58 and 37.46?µg/mL respectively. These results can provide a background for future research into the benefits of chickpea lectin to pharmacological perspective.     

Identification of D-amino acid dehydrogenase as an upstream regulator of the autoinduction of a putative acyltransferase in <Emphasis Type="Italic">Corynebacterium glutamicum</Emphasis>

Expression of a putative acyltransferase encoded by NCgl- 0350 of Corynebacterium glutamicum is induced by cell-free culture fluids obtained from stationary-phase growth of both C. glutamicum and Pseudomonas aeruginosa, providing evidence for interspecies communication. Here, we further confirmed that such communication occurs by showing that acyltransferase expression is induced by culture fluid obtained from diverse Gram-negative and -positive bacterial strains, including Escherichia coli, Salmonella Typhimurium, Bacillus subtilis, Staphylococcus aureus, Mycobacterium sp. strain JC1, and Mycobacterium smegmatis. A homologous acyltransferase encoded by PA5238 of P. aeruginosa was also induced by fluids obtained from P. aeruginosa as well as other bacterial strains, as observed for NCgl0350 of C. glutamicum. Because C. glutamicum is difficult to study using molecular approaches, the homologous gene PA5238 of P. aeruginosa was used to identify PA5309 as an upstream regulator of expression. A homologous D-amino acid dehydrogenase encoded by NCgl- 2909 of C. glutamicum was cloned based on amino acid similarity to PA5309, and its role in the regulation of NCgl0350 expression was confirmed. Moreover, NCgl2909 played positive roles in growth of C. glutamicum. Thus, we identified a D-amino acid dehydrogenase as an upstream regulator of the autoinduction of a putative acyltransferase in C. glutamicum.     

Salt stress induced soybean <Emphasis Type="Italic">GmIFS1</Emphasis> expression and isoflavone accumulation and salt tolerance in transgenic soybean cotyledon hairy roots and tobacco

Effects of isoflavones on plant salt tolerance were investigated in soybean (Glycine max L. Merr. cultivar N23674) and tobacco (Nicotiana tabacum L.). Leaf area, fresh weight, net photosynthetic rate (Pn), and transpiration rate (Tr) of soybean N23674 plants treated with 80 mM NaCl were significantly reduced, while a gene (GmIFS1) encoding for 2-hydroxyisoflavone synthase was highly induced, and isoflavone contents significantly increased in leaves and seeds. To test the impact of isoflavones to salt tolerance, transgenic soybean cotyledon hairy roots expressing GmIFS1 (hrGmIFS1) were produced. Salt stress slightly increased isoflavone content in hairy roots of the transgenic control harboring the empty vector but substantially reduced the maximum root length, root fresh weight, and relative water content (RWC). The isoflavone content in hrGmIFS1 roots, however, was significantly higher, and the above-mentioned root growth parameters decreased much less. The GmIFS1 gene was also transformed into tobacco plants; plant height and leaf fresh weight of transgenic GmIFS1 tobacco plants were much greater than control plants after being treated with 85 mM NaCl. Leaf antioxidant capacity of transgenic tobacco was significantly higher than the control plants. Our results suggest that salt stress-induced GmIFS1 expression increased isoflavone accumulation in soybean and improved salt tolerance in transgenic soybean hairy roots and tobacco plants.     

Activities of Adenylate Cyclase and Changes in cAMP Concentration in Root Cells of Pea Seedlings Infected with Mutualists and Phytopathogens

Work was carried out on pea (Pisum sativum L.) seedling roots to assess the attachment of the nitrogen-fixing symbiotic bacteria Rhizobium leguminosarum bv. vicea (Rlv) and the bacterial phytopathogens—specific Pseudomonas syringae pv. pisi (Psp) and nonspecific Clavibacter michiganensis ssp. sepedonicus (Cms). Different root zones were examined: (I) the meristem, 2 mm from the root tip; (II) the root hair-free zone, 27 mm; (III) the zone of root hair anlages, 712 mm; (IV) the young root hair zone, 1217 mm; and (V) the zone of root hair that completed the growth, 1722 mm. It was found earlier that the zones differed in their susceptibility to Rlv. In the present work, reactions of particular components of the adenylate cyclase signaling system (ACSS) were estimated, i.e., concentration of cAMP and activities of transmembrane adenylate cyclase (tAC) and soluble adenylate cyclase (sAC) in these zones after different times post inoculation (5, 15, 120, and 360 min). It was revealed that the degree of activation of particular components of ACSS did not depend on the sorption rate of differently specialized bacteria. Upon contact with Rlv, the character of changes in tAC and sAC activities was almost the same in different root zones and resembled the dynamics of the cAMP content. Inoculation with Psp changed the cAMP level similarly to that with Rlv, but the dynamics of tAC and sAC was opposite to each other in most cases. Inoculation with Cms, in spite of the absence of its attachment, elevated the cAMP content and activated tAC and sAC. It is suggested that the above-mentioned changes in ACSS is associated with exometabolites of Rlv, Psp, and Cms, which activate the PAMP-induced immunity of the pea seedling cells. The uniform dynamics of cAMP in different root zones upon the exposure to Rlv and Psp seems to reflect the specific reaction and, presumably, fulfills different functions—regulatory with Rlv and defensive with Psp. Upon short-term contact with Cms, the cAMP dynamics in the same root zones displayed a nonspecific character that might be related to the rate of adsorption of exopolysaccharides by the root hair. The systemic response of ACSS was observed in the hypocotyls of the seedlings exposed to any of the three organisms.     

Integration of sudden death syndrome resistance loci in the soybean genome

Key message

Complexity and inconsistencies in resistance mapping publications of soybean sudden death syndrome (SDS) result in interpretation difficulty. This review integrates SDS mapping literature and proposes a new nomenclature system for reproducible SDS resistance loci.

Abstract

Soybean resistance to sudden death syndrome (SDS) is composed of foliar resistance to phytotoxins and root resistance to pathogen invasion. There are more than 80 quantitative trait loci (QTL) and dozens of single nucleotide polymorphisms (SNPs) associated with soybean resistance to SDS. The validity of these QTL and SNPs is questionable because of the complexity in phenotyping methodologies, the disease synergism between SDS and soybean cyst nematode (SCN), the variability from the interactions between soybean genotypes and environments, and the inconsistencies in the QTL nomenclature. This review organizes SDS mapping results and proposes the Rfv (resistance to Fusarium virguliforme) nomenclature based on supporting criteria described in the text. Among ten reproducible loci receiving our Rfv nomenclature, Rfv18-01 is mostly supported by field studies and it co-localizes to the SCN resistance locus rhg1. The possibility that Rfv18-01 is a pleiotropic resistance locus and the concern about Rfv18-01 being confounded with Rhg1 is discussed. On the other hand, Rfv06-01, Rfv06-02, Rfv09-01, Rfv13-01, and Rfv16-01 were identified both by screening soybean leaves against phytotoxic culture filtrates and by evaluating SDS severity in fields. Future phenotyping using leaf- and root-specific resistance screening methodologies may improve the precision of SDS resistance, and advanced genetic studies may further clarify the interactions among soybean genotypes, F. virguliforme, SCN, and environments. The review provides a summary of the SDS resistance literature and proposes a framework for communicating SDS resistance loci for future research considering molecular interactions and genetic breeding for soybean SDS resistance.

     

A major QTL (<Emphasis Type="Italic">qFT12.1</Emphasis>) allele from wild soybean delays flowering time

Soybean is highly sensitive to photoperiod. To improve the adaptability and productivity of soybean, it is essential to understand the molecular mechanisms regulating flowering time. To identify new flowering time QTLs, we evaluated a BC₃F₅ population consisting of 120 chromosome segment substitution lines (CSSLs) over 2 years under field conditions. CSSLs were derived from a cross between the cultivated soybean cultivar Jackson and the wild soybean accession JWS156-1, followed by continuous backcrossing using Jackson as the recurrent parent. Four QTLs (qFT07.1, qFT12.1, qFT12.2, and qFT19.1) were detected on three chromosomes. Of these, qFT12.1 showed the highest effect, accounting for 36.37–38.27% of the total phenotypic variation over 2 years. This QTL was further confirmed in the F₇ recombinant inbred line population (n?=?94) derived from the same cross (Jackson × JWS156-1). Analysis of the qFT12.1 BC₃F₅ residual heterozygous line RHL509 validated the allele effect of qFT12.1 and revealed that the recessive allele of qFT12.1 resulted in delayed flowering. Evaluating the qFT12.1 near-isogenic lines (NILs) under different growth conditions showed that NILs with the wild soybean genotype always showed later flowering than those with the cultivated soybean genotype. qFT12.1 was delimited to a 2703-kb interval between the markers BARCSOYSSR_12_0220 and BARCSOYSSR_12_0368 on chromosome 12. qFT12.1 may be a new flowering time gene locus in soybean.