A lack of complete resistance in the current germplasm complicates the management of Sclerotinia stem rot (SSR) caused by
Sclerotinia sclerotiorum
in soybean. In this study, we used bean pod mottle ...virus (BPMV) as a vehicle to down-regulate expression of a key enzyme in the production of an important virulence factor in
S. sclerotiorum
, oxalic acid (OA). Specifically, we targeted a gene encoding oxaloacetate acetylhydrolase (
Ssoah1
), because
Ssoah1
deletion mutants are OA deficient and non-pathogenic on soybean. We first established that
S. sclerotiorum
can uptake environmental RNAs by monitoring the translocation of Cy3-labeled double-stranded and small interfering RNA (ds/siRNAs) into fungal hyphae using fluorescent confocal microscopy. This translocation led to a significant decrease in
Ssoah1
transcript levels
in vitro
. Inoculation of soybean plants with BPMV vectors targeting
Ssoah1
(pBPMV-OA) also led to decreased expression of
Ssoah1
. Importantly, pBPMV-OA inoculated plants showed enhanced resistance to
S. sclerotiorum
compared to empty-vector control plants. Our combined results provide evidence supporting the use of HIGS and exogenous applications of ds/siRNAs targeting virulence factors such as OA as viable strategies for the control of SSR in soybean and as discovery tools that can be used to identify previously unknown virulence factors.
Key message
This study focused on enhancing resilience of soybean crops to drought and salinity stresses by overexpression of
GmFAD3A
gene, which plays an important role in modulating membrane ...fluidity and ultimately influence plants response to various abiotic stresses.
Fatty acid desaturases (FADs) are a class of enzymes that mediate desaturation of fatty acids by introducing double bonds. They play an important role in modulating membrane fluidity in response to various abiotic stresses. However, a comprehensive analysis of
GmFAD3
in drought and salinity stress tolerance in soybean is lacking. We used bean pod mottle virus (BPMV)-based vector for achieving rapid and efficient overexpression as well as silencing of
Omega-3 Fatty Acid Desaturase
gene from
Glycine max
(
GmFAD3
) to assess the functional role of
GmFAD3
in abiotic stress responses in soybean. Higher levels of recombinant BPMV-
GmFAD3A
transcripts were detected in overexpressing soybean plants. Overexpression of
GmFAD3A
in soybean resulted in increased levels of jasmonic acid and higher expression of
GmWRKY54
as compared to mock-inoculated, vector-infected and FAD3-silenced soybean plants under drought and salinity stress conditions. The
GmFAD3A
-overexpressing plants showed higher levels of chlorophyll content, efficient photosystem-II, relative water content, transpiration rate, stomatal conductance, proline content and also cooler canopy under drought and salinity stress conditions as compared to mock-inoculated, vector-infected and FAD3-silenced soybean plants. Results from the current study revealed that
GmFAD3A
-overexpressing soybean plants exhibited tolerance to drought and salinity stresses. However, soybean plants silenced for
GmFAD3
were vulnerable to drought and salinity stresses.
Bean pod mottle virus (BPMV) is a viral pathogen found in virtually all soybean fields in Mississippi during recent surveys. A study was undertaken to better understand the local population of this ...virus and to investigate sources of primary inoculum. Investigation of the local BPMV population was carried out by sequencing and comparison of four genomic regions of numerous isolates collected from research and production fields throughout Mississippi. All studied isolates showed great molecular uniformity with the exception of two, which appeared distinct in the RNA-dependent RNA polymerase region. Sequencing of the complete RNA-1 segments for these two isolates is currently on-going. In a study on sources of early infections, several plant species were identified as new hosts with possible roles in the epidemiology of this virus in the Southeastern United States.
Integrated disease management requires a thorough understanding of pathogen-plant-environment interactions in order to develop cost-effective management programs. Knowing pre-plant risk factors ...associated with Bean pod mottle virus (BPMV) would enable soybean producers to deploy management practices that delay early season BPMV infection and spread to minimize negative impacts on soybean yield and quality. Potential abiotic and biotic BPMV risk factors identified by correlation analysis were evaluated using regression analysis to quantify the predictive power of single and combined factors at the county scale. We examined thirteen factors: county centroid latitude, longtitude, and elevation; soybean planting date, number of soybean farms, and soybean acres; number of alfalfa acres harvested; for the period of October through April, number of days with daily mean temperature < 0C, number of days with snow cover, consecutive days with maximum temperature < 0C, consecutive days with snow cover, and accumulated snow depth; and for March, number of days with mean temperature below 0C. Variables with highest predictive value for BPMV incidence were days with mean temperatures < 0C in March and number of soybean farms within Iowa counties, with partial coefficients -4.03 (X sub(1)), and -0.012 (X sub(2)), respectively. The multiple regression model explained 54.5% of the variation in county-scale BPMV incidence; higher BPMV incidence was associated with days in March with mean temperatures < 0C (X sub(1)) and fewer soybean farms per county (X sub(2)). Thus, we suggest that using the March temperature data and the number of soybean farms/county, potential BPMV incidence can be predicted before planting. Pre-plant predictions can aid soybean growers and seed companies in making management decisions, such as the need for seed and/or foliar insecticide treatments, and selection of planting sites with reduced risk.
It is increasingly clear that microbial plant symbionts can influence interactions between their plant hosts and other organisms. However, such effects remain poorly understood, particularly under ...ecologically realistic conditions where plants simultaneously interact with diverse mutualists and antagonists. Here, we examine how the effects of a plant virus on indirect plant defences against its insect vector are influenced by co-occurrence of other microbial plant symbionts. Using a multi-factorial design, we manipulated colonization of soya bean using three different microbes: a pathogenic plant virus (bean pod mottle virus (BPMV)), a nodule-forming beneficial rhizobacterium ( Bradyrhizobium japonicum) and a plant growth-promoting rhizobacterium ( Delftia acidovorans). We then assessed recruitment of parasitoids ( Pediobious foveolatus (Eulophidae)) and parasitism rates following feeding by the BPMV vector Epilachna varivestis (Coccinellidae). BPMV infection suppressed parasitoid recruitment, prolonged parasitoid foraging time and reduced parasitism rates in semi-natural foraging assays. However, simultaneous colonization of BPMV-infected hosts by both rhizobacteria restored parasitoid recruitment and rates of parasitism to levels similar to uninfected controls. Co-colonization by the two rhizobacteria also enhanced parasitoid recruitment in the absence of BPMV infection. These results illustrate the potential of plant-associated microbes to influence indirect plant defences, with implications for disease transmission and herbivory, but also highlight the potential complexity of such interactions.
Summary
Plant diseases inflict heavy losses on soybean yield, necessitating an understanding of the molecular mechanisms underlying biotic/abiotic stress responses. Ca2+ is an important universal ...messenger, and protein sensors, prominently calmodulins (CaMs), recognize cellular changes in Ca2+ in response to diverse signals. Because the development of stable transgenic soybeans is laborious and time consuming, we used the Bean pod mottle virus (BPMV)‐based vector for rapid and efficient protein expression and gene silencing. The present study focuses on the functional roles of the gene encoding the soybean CaM isoform GmCaM4. Overexpression of GmCaM4 in soybean resulted in enhanced resistance to three plant pathogens and increased tolerance to high salt conditions. To gain an understanding of the underlying mechanisms, we examined the potential defence pathways involved. Our studies revealed activation/increased expression levels of pathogenesis‐related (PR) genes in GmCaM4‐overexpressing plants and the accumulation of jasmonic acid (JA). Silencing of GmCaM4, however, markedly repressed the expression of PR genes. We confirmed the in vivo interaction between GmCaM4 and the CaM binding transcription factor Myb2, which regulates the expression of salt‐responsive genes, using the yeast two‐hybrid (Y2H) system and bimolecular fluorescence complementation assays. GmCaM4 and Glycine max CaM binding receptor‐like kinase (GmCBRLK) did not interact in the Y2H assays, but the interaction between GmCaM2 and GmCBRLK was confirmed. Thus, a GmCaM2–GmCBRLK‐mediated salt tolerance mechanism, similar to that reported in Glycine soja, may also be functional in soybean. Confocal microscopy showed subcellular localization of the green fluorescent protein (GFP)‐GmCaM4 fusion protein in the nucleus and cytoplasm.
Halo blight disease of beans is caused by a gram-negative bacterium, Pseudomonas syringae pv. phaseolicola. The disease is prevalent in South America and Africa and causes crop loss for indigent ...people who rely on beans as a primary source of daily nutrition. In susceptible beans, P. syringae pv. phaseolicola causes water-soaking at the site of infection and produces phaseolotoxin, an inhibitor of bean arginine biosynthesis. In resistant beans, P. syringae pv. phaseolicola triggers a hypersensitive response that limits the spread of infection. Here, we used high-throughput mass spectrometry to interrogate the responses to two different P. syringae pv. phaseolicola isolates on a single line of common bean, Phaseolus vulgaris PI G19833, with a reference genome sequence. We obtained quantitative information for 4,135 bean proteins. A subset of 160 proteins with similar accumulation changes during both susceptible and resistant reactions included salicylic acid responders EDS1 and NDR1, ethylene and jasmonic acid biosynthesis enzymes, and proteins enabling vesicle secretion. These proteins revealed the activation of a basal defense involving hormonal responses and the mobilization of extracellular proteins. A subset of 29 proteins specific to hypersensitive immunity included SOBIR1, a G-type lectin receptor–like kinase, and enzymes needed for glucoside and phytoalexin production. Virus-induced gene silencing revealed that the G-type lectin receptor–like kinase suppresses bacterial infection. Together, the results define the proteomics of disease resistance to P. syringae pv. phaseolicola in beans and support a model whereby the induction of hypersensitive immunity reinstates defenses targeted by P. syringae pv. phaseolicola.
The soybean aphid (Aphis glycines Matsumura) is an economically important invasive pest of soybean. In addition to damage caused by soybean aphid feeding on the phloem sap, this insect also transmits ...many plant viruses, including soybean mosaic virus (SMV). Previous work has shown that plant viruses can change plant host phenotypes to alter the behavior of their insect vectors to promote virus spread, known as the vector manipulation hypothesis. In this study, we used electropenetography (EPG) to examine the effects of two plant viruses on soybean aphid feeding behavior: SMV, which is transmitted by many aphid species including the soybean aphid, and bean pod mottle virus (BPMV), which is transmitted by chrysomelid and some coccinellid beetles but not aphids. These two viruses often co-occur in soybean production and can act synergistically. Surprisingly, our results showed little to no effect of SMV on soybean aphid feeding behaviors measured by EPG, but profound differences were observed in aphids feeding on BPMV-infected plants. Aphids took longer to find the vascular bundle of BPMV-infected plants, and once found, spent more time entering and conditioning the phloem than ingesting phloem sap. Interestingly, these observed alterations are similar to those of aphids feeding on insect-resistant soybean plants. The cause of these changes in feeding behavior is not known, and how they impact virus transmission and soybean aphid populations in the field will require further study.
Bean pod mottle virus (BPMV) is a wide-spread and destructive virus that causes huge economic losses in many countries every year. A sensitive, reliable and specific method for rapid surveillance is ...urgently needed to prevent further spread of BPMV.
A degenerate reverse-transcription loop-mediated isothermal amplification (RT-LAMP) primer set was designed on the conserved region of BPMV CP gene. The reaction conditions of RT-LAMP were optimized and the feasibility, specificity and sensitivity of this method to detect BPMV were evaluated using the crude RNA rapidly extracted from soybean seeds.
The optimized RT-LAMP parameters including 6 mM MgCl2, 0.8 M betaine and temperature at 62.5-65°C could successfully amplify the ladder-like bands from BPMV infected soybean seeds. The amplification was very specific to BPMV that no cross-reaction was observed with other soybean viruses. Inclusion of a fluorescent dye makes it easily be detected in-tube by naked eye. The sensitivity of RT-LAMP assay is higher than the conventional RT-PCR under the conditions tested, and the conventional RT-PCR couldn't be used for detection of BPMV using crude RNA extract from soybean seeds.
A highly efficient and practical method was developed for the detection of BPMV in soybean seeds by the combination of rapid RNA extraction and RT-LAMP. This RT-LAMP method has great potential for rapid BPMV surveillance and will assist in preventing further spread of this devastating virus.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Soybean, one of the world's most important sources of animal feed and vegetable oil, can be infected by numerous viruses. However, only a small number of the viruses that can potentially infect ...soybean are considered as major economic problems to soybean production. Therefore, we consider management options available to control diseases caused by eight viruses that cause, or have the potential to cause, significant economic loss to producers. We summarize management tactics in use and suggest direction for the future. Clearly, the most important tactic is disease resistance. Several resistance genes are available for three of the eight viruses discussed. Other options include use of virus-free seed and avoidance of alternative virus hosts when planting. Attempts at arthropod vector control have generally not provided consistent disease management. In the future, disease management will be considerably enhanced by knowledge of the interaction between soybean and viral proteins. Identification of genes required for soybean defense may represent key regulatory hubs that will enhance or broaden the spectrum of basal resistance to viruses. It may be possible to create new recessive or dominant negative alleles of host proteins that do not support viral functions but perform normal cellular function. The future approach to virus control based on gene editing or exploiting allelic diversity points to necessary research into soybean-virus interactions. This will help to generate the knowledge needed for rational design of durable resistance that will maximize global production.
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