Biocontrol of Fusarium spp. in vitro and in vine cuttings using Bacillus sp. F62

Fusarium spp., the causal agent of Fusarium wilt, cause substantial economic losses in viticulture, mainly in tropical regions. This study aimed to assess the biocontrol potential of Bacillus sp. F62 against Fusarium spp., both in vitro and in rootstock cuttings of the SO4 variety. To this end, the in vitro antagonism was evaluated through diffusible and volatile compounds synthesized by Bacillus sp. F62 on three Fusarium spp. isolates. Subsequently, the isolate FusA06-18 was selected for a rootstock cutting experiment. The vine cuttings underwent the following treatments: control, pathogen inoculation (Fus), bacterial inoculation (Bac), and bacterial followed by pathogen inoculation (Bac + Fus). Our findings revealed an average reduction of 39.1% in the mycelial growth of the pathogen through dual culture assay and a decrease of 11.6% in the Fusarium spp. radial growth due to the effects of volatile compounds. In the experiment with vine cuttings, applying Bacillus sp. F62 reduced the pathogen re-isolation frequency from 81.7% (Fus) to 63.3% (Bac + Fus). Therefore, Bacillus sp. F62 effectively suppressed the mycelial growth of Fusarium spp. and reduced the Fusarium wilt incidence in vine cuttings of the rootstock ‘SO4’

The effects of high-monosaccharide diets on development and biochemical composition of white-eyed mutant strain of house cricket (Acheta domesticus)

Tryptophan (TRP) is one of the essential amino acids in the animal body. Its exogenicity and low concentrations mean that it can be regarded as one of the key regulatory molecules at the cellular as well as physiological level. It has been shown to have a number of essential functions, such as in the production of other biologically active molecules. The main objective of this project was to investigate the effects of a high monosaccharide diet (HMD) on a hemimetabolic insect-house cricket (Acheta domesticus) and a mutant strain with impaired visual pigment synthesis (closely related to the tryptophan and kynurenine (KYN) metabolic pathway)-white eye. This study was aimed at determining the effects of glucose and fructose on cricket development and biochemical composition. A parallel goal was to compare the response of both cricket strains to HMD. ELISA assays indicated dysfunction of the TRP-KYN pathway in white strain insects and an elevated KYN/TRP ratio. Biochemical analyses demonstrated the effects of HMD mainly on fat and glycogen content. A decrease in food intake was also observed in the groups on HMD. However, no changes in imago body weight and water content were observed. The results of the study indicate a stronger response of the white strain to HMD compared to the wild-type strain. At the same time, a stronger detrimental effect of fructose than of glucose was apparent. Sex was found to be a modulating factor in the response to HMD

The relationship between cutinases and the pathogenicity/virulence of Fusarium solani in potato tubers

Cutinase activity was spectrophotometrically determined in the culture supernatants of 40 isolates of Fusarium solani, obtained in Iran from various biological origins and grown in a minimal medium with 0.4% cutin as the only carbon source. Enzymatic activities, which ranged from 0 to 488 nmol min-1 mL-1, were related to the pathogenicity or virulence of the fungal isolates, determined on potato tubers using a 0–5 disease severity scale. Cutinase activity was either not detected at all or was very low in the non-pathogenic isolates, whereas it was directly correlated with the virulence of the pathogenic isolates (Radj 2 = 0.97), with an increase in cutinase activity of about 100 units corresponding to a one-point increase in the disease severity scale. SDS-PAGE analysis revealed that non-pathogenic F. solani isolates did not produce a cutinase band, while pathogenic isolates, with various degrees of virulence, produced single or double peptide bands with molecular weights of 20–23 kDa. We conclude that enzyme activity can be used as a predictive marker of the pathogenicity and virulence of F. solani isolates obtained from various hosts

Dissecting and modelling the comparative adaptation to water limitation of sorghum and maize: role of transpiration efficiency, transpiration rate and height

Maize is considered less drought-tolerant than sorghum, but sorghum is commonly grown as a short triple dwarf (3dwarf) type, so difference in plant height confounds the species comparison. The objectives of this study were to experimentally determine effects of species and plant height differences on transpiration efficiency (TE) and transpiration rate per unit green leaf area (TGLA) and use findings to explain input parameters in a simulation study on the comparative adaptation of 3dwarf sorghum and maize in environments with contrasting water availability. Maize, tall double dwarf (2dwarf) and short 3dwarf sorghum genotypes were grown in two lysimeter experiments in 2011 in SE Queensland, Australia. Each plant was harvested after anthesis and total transpiration, shoot and root dry mass were measured to estimate TE. Daily TGLA was used to compare transpiration rates. Species and height had limited effect on TE, but significantly affected TGLA. This was associated with differences in biomass allocation. The similar TE but higher TGLA in maize compared with 3dwarf sorghum meant it potentially produces more biomass, consistent with published differences in biomass accumulation and radiation use efficiency (RUE). The simulation study, which used similar TE for maize and 3dwarf sorghum, but captured differences in TGLA through differences in RUE, predicted crossover interactions for grain yield between species and total water use. The greater TGLA of maize decreased grain yield in water-limited environments, but increased yields in well-watered situations. Results highlight that similarity in TE and differences in TGLA can influence comparative adaptation to water limitation

The nitrous oxide reductase of Neisseria gonorrhoeae is a transcriptionally active yet translationally silent potogene

Many parasitic organisms undergo reductive evolution, the process of losing genes which are now redundant since nutrients can be acquired from the host (Gómez-Valero et al., 2007). Such shortening of the genome may confer a selective advantage upon cell division (D’Souza et al., 2014). The bacterium Neisseria gonorrhoeae is an example of a niche specialist. This obligate human pathogen survives in the urogenital tract, a microaerobic environment, via denitrification. During denitrification, nitrogen oxides (NOX) can be reduced from nitrate (NO3-) to dinitrogen (N2) by a series of metalloenzymes as the terminal electron acceptors in oxidative phosphorylation instead of O2 (Barth et al., 2009a). N. gonorrhoeae acquires both NOx and the metal ion cofactors needed for denitrification from the host. The key metal is copper (Cu), which is leached from intrauterine contraceptive devices used by a high percentage of women (Crandell and Mohler, 2021). In rare instances when an immune response to N. gonorrhoeae is induced, host phagosomal Cu level is elevated (Djoko et al., 2015), yet gonococci cells survive (Château and Seifert, 2016). Whilst expressing several respiratory cuproenzymes needed for growth and surviving high Cu level, N. gonorrhoeae lacks proteins from the Cue, Cso, Cus and Cop systems for Cu sensing and export (Andrei et al., 2020). Little is known generally about how bacteria acquire and insert Cu into cuproenzymes (Stewart et al., 2019). N. gonorrhoeae possesses a truncated denitrification pathway; the nitrate reductase (nar/nap) operon is absent and the nitrous oxide reductase (nos) operon is nonsense-mutated. The nitrous oxide reductase enzyme, NosZ, catalyses reduction of nitrous oxide (N2O) to dinitrogen (N2). This reaction is the last in the denitrification pathway and is catalysed by a CuZ site. The nos operon consists of six genes (nosRZDFYL). There is a single nonsense substitution in each of the following gonococcal genes: nosR (the putative transcription regulator and electron donor to NosZ), nosZ (the reductase enzyme) and nosD (part of the Cu delivery system to NosZ). These mutations are unique to N. gonorrhoeae among Neisseria, suggesting they evolved after speciation from N. meningitidis. In NosZ, the nonsense-truncated protein would lack the C-terminal CuA site implicated in electron transfer to CuZ. Hence, the gonococcal nosZ has thus long been assumed to be a non-functional “pseudo” gene (Barth et al., 2009a; Overton et al., 2006). The premature stop codons in gonococcal nos are conserved across different strains. It is unclear how N. gonorrhoeae may benefit from inactivation of NosZ, particularly in a microaerobic Cu-rich environment (such as that generated by a Cu contraceptive). Hence, we were interested in the possibility that stop codon suppression may be occurring in the gonococcal nos mRNA. In recent decades, much work has been done on how premature stop codons can be readthrough (Feng et al., 2022), and how supposed pseudogenes possess functionality (Li et al., 2013). This has led to authors coining the terms pseudo-pseudogene for putative pseudogenes which are actually functional (Prieto-Godino et al., 2016) and potogene for DNA sequences which have potential to evolve into novel genes (Brosius and Gould, 1992). Under low Cu levels, the Paracoccus denitrificans NosZ polypeptide is subject to degradation such that a truncated NosZ lacking the C-terminal CuA domain accumulates in the periplasm which still retains activity (Felgate et al., 2012). While the product of gonococcal denitrification has been determined to be N2O, not N2 (Lissenden et al., 2000), the presence of a NosZ protein in N. gonorrhoeae has yet to be experimentally tested. In this study, we investigated the expression of the gonococcal nos operon and NosZ protein. Our research shows the gonococcal nos operon is fully transcribed and upregulated by NO2-, but a ∆nosZ strain has no distinct phenotype versus the WT. This corroborates other studies which found transcriptionally active but phenotypically silent gonococcal genes (Takahashi and Watanabe, 2005). Expression of the gonococcal nos operon was not found to be influenced by Cu, contradicting findings from other bacterial species that Cu upregulates nos expression (Felgate et al., 2012; Sullivan et al., 2013; Woolfenden et al., 2013). Despite transcription, we have determined the NosZ protein is not stably expressed. Supplementation of 1 and 10 µM Cu in N. gonorrhoeae cultures does not generate a detectable NosZ protein. We suggest this lack of a stable gonococcal NosZ protein may be due to nonsense mutations in the nosRZD genes causing degradation of the nascent polypeptide, or inhibition of translation by mRNA secondary structures such as hairpins. Other Neisseria thought to lack NosZ include N. meningitidis, another obligate human pathogen (Stephens, 2009) and N. mucosa, an emerging opportunistic human pathogen (Osses et al., 2017). N. meningitidis has a deletion from the middle of nosR to the middle of nosD, eliminating the catalytic subunit nosZ, in addition to premature stop codons in nosY and nosX, while N. mucosa contains a premature stop codon within nosZ and a deletion in nosF (Barth et al., 2009a). Commensal Neisseria species largely retain a functioning denitrification pathway. We propose the pathogenic Neisseria independently lost the requirement for N2O reduction by either acquiring some yet unknown alternative respiratory mechanism, or compensation by the host minimising the need for the last step of denitrification. Alternatively, the nos mRNA transcripts in these species may have an unknown regulatory role which provides a selective advantage (Kamieniarz-Gdula and Proudfoot, 2019). We hope these findings may contribute to an increased understanding of potogenes, as well as the evolution and pathogenicity of Neisseria species. Determining the evolutionary drivers behind this loss of protein expression in pathogenic Neisseria species is an objective for future research

Plant Lectins with Insecticidal and Insectistatic Activities

Lectins are an important group of proteins which are spread in all kingdoms of life. Their most lighted characteristic is associated to their specific carbohydrate binding, although function has been not even identified. According to their carbohydrate specificity, several biological activities have been assessed, finding that lectins can be used as mitogenic agents, biomarkers, and cytotoxic and insecticide proteins. Lectins have been classified according to several features such as structure, source, and carbohydrate recognition. The Protein Research Group (PRG) has worked on Colombian seeds from the family of Fabaceae and Lamiaceae plants, isolating and characterizing their lectins, and found more than one lectin in some plants, indicating that according to its specificity, different lectins can have different biological activities. In the case of legume domain lectins, they have shown the biggest potential as insecticide or insectistatic agents due to the glycosylation pattern in insect midgut cells. This review attempts to identify the characteristics of plant legume lectin domains that determine their insecticidal and insectistatic activities

Biological control of chocolate spot and rust on faba beans

The potential of bacterial and fungal isolates from root and soil samples of faba bean and other crops, was assessed for biological control of Botrytis fabae (chocolate spot) and rust (Uromyces viclae-fabae) through in vitro and in vivo screening. In total, 690 bacterial and fungal isolates were obtained and screened with B. fabae mycelium in a preliminary screen on agar plates. Potential antagonism was exhibited by approximately 30% of these isolates, as indicated by at least one of the following visual symptoms: a brown discoloration of mycelium or media, a zone of inhibition of mycelial growth, a zone free of sclerotial formation or contact inhibition between isolates. Detached leaf studies rejected a further 20% of the isolates due to their pathogenicity towards the leaves. Further replicated antagonism tests in vitro allowed more detailed studies, where the percentage inhibition in radial growth of B. fabae and the zone of inhibition were recorded. Some isolates which exhibited potential antagonism in the initial preliminary screen did not do so in this test. Bacterial isolate LL1.F23, identified as Pseudomonas fluorescens, exhibited the largest inhibition zone (11.2 mm), inducing malformations and severe browning of mycelium at the culture edge. Overall, fungi produced smaller inhibition zones than bacterial isolates. Germination tests with B. fabae conidia showed that isolate LL1.F23 significantly reduced the germination, length of germ-tubes produced and appressorium formation relative to the control. Other isolates reduced germination significantly but to a lesser degree. Some fungal isolates inhibited mycelial growth of B. fabae through the production of volatile and nonvolatile antibiotics. However, due to the production of secondary colonies of antagonists, the results were variable and inconsistent. Spore germination tests on V. viclae-fabae in the presence of antagonists showed that uredospore germination was reduced by up to 90%. Following in vitro screening, 35 isolates (15 fungal and 20 bacterial isolates) were chosen for application to bean plants in the glasshouse. Against chocolate spot, the fungal isolate AP1.S20 (Penicillium chrysogenum Thom.) showed the greatest potential, reducing disease levels by up to 80%. Fungal isolate AG1.F4 (Geomyces pannorus (Link) Singler and J.W. Carmich.) and bacterial isolate P1.S13B, reduced chocolate spot infection to 19% and 12% of the control respectively, when applied simultaneously with B. fabae conidia. The percentage leaf area covered with rust pustules was reduced by 78% following simultaneous application of isolate AP2.R16 with rust uredospores. The most consistent reductions in chocolate spot and rust were obtained with simultaneous inoculation of the antagonist and the pathogen. It was found with rust that the greater the concentration of antagonist inoculum, the greater the reduction of rust on the leaf surface. A suspension of 1 x 10

The impact of salicylic acid on some physiological responses of Artemisia aucheri Boiss. under in vitro drought stress

Salicylic acid (SA) is an important plant regulator which is involved in growth, development, and response to stress. This study was aimed to evaluate some physiological and biochemical responses of Artemisia aucheri Boiss. under drought stress after exogenous SA treatment. Experiment was performed in vitro. Polyethylene glycol (PEG/6000) with 0, 2 and 4 % (w/v) was used in MS medium to simulate drought stress and different concentrations of SA (0, 0.01 and 0.1mM) were added. After four weeks, SA alleviated the negative effects of PEG on dry and fresh mass as well as chlorophyll and carotenoid contents. Under drought stress, application of SA decreased storage polysaccharides and increased soluble carbohydrates respectively. Although PEG had no significant effect on flavonoid content, it increased significantly anthocyanin and total phenol content, total antioxidant capacity, PAL (phenylalanine ammonia-lyase) and TAL (tyrosine ammonia-lyase) activity and SA treatment improved these parameters significantly. According to the current data, it was concluded that SA increased drought tolerance of Artemisia aucheri by increasing biosynthesis of phenolic compounds, improvement of TAL and PAL activity as well as also by increased content of soluble carbohydrates