Transcriptome reanalysis and gene expression of 13 detoxification genes for avermectin and pyridaben resistance in Panonychus citri.

Citrus red mites (P. citri) are key pests affecting citrus production worldwide due to pesticide resistance. The resistance mechanisms of ten pesticides are known, but a comprehensive study using transcriptome data is missing. This study employed deeptools, cuffdiff, rmats, bcftools and other software to examine gene expression variation, alternative splicing (AS), and mutations in mite resistance. The research highlighted that pesticides can regulate gene transcription, and red mites with resistance increase cytochrome P450, glutathione S-transferases, carboxylesterase, and acetylcholinesterase expression. Pyridaben also induces new AS events. Fluazinam-induced mites show mRNA splicing peaking earlier than transcription, both peaking at one day and returning to baseline after two days. AS profiles are similar in different mite populations with overlapping pesticide resistances. Lastly, specific mitochondrial SNPs in mites might mediate resistance against select pesticides.

Citrus Fruits Produce Direct Defense Responses against Oviposition by Bactrocera minax (Diptera: Tephritidae).

Plants perceive and orchestrate defense responses when herbivorous insects are ovipositing. Fruits, as a crucial reproductive organ in plants, have rarely been researched on the responses to insect eggs. Here, we found that oviposition by the specialist insect Bactrocera minax in navel oranges activated the lignin synthesis pathway and cell division, causing mechanical pressure that crushed the eggs. Transcriptome and metabolome analyses revealed an enrichment of oviposition-induced genes and metabolites within the lignin synthesis pathway, which was confirmed by histochemical staining. Furthermore, hydrogen peroxide (H2O2) accumulation was observed at the oviposition sites. Plant defense-related hormones jasmonic acid (JA) and salicylic acid (SA) exhibited rapid induction after oviposition, while indole-3-acetic acid (IAA) activation occurred in the later stages of oviposition. Additionally, secondary metabolites induced by prior egg deposition were found to influence larval performance. Our studies provide molecular evidence that host fruits have evolved defense mechanisms against insect eggs and pave the way for future development of insect-resistant citrus varieties.

Funneliformis mosseae potentiates defense mechanisms of citrus rootstocks against citrus nematode, Tylenchulus semipenetrans.

Using integrated pest management without relying on chemical pesticides is one of the most attractive approaches to controlling plant pathogens. Among them, using resistant cultivars or rootstocks against diseases in combination with beneficial microorganisms has attracted special attention. The citrus nematode is one of the major constraints of citrus cultivation worldwide. We showed that the mycorrhizal arbuscular fungus, Funneliformis mosseae, increased growth parameters including shoot and root length and biomass of two main rootstocks of citrus, sour orange and Volkamer lemon, in noninfected and infected plants with citrus nematode. It decreased the infection rate by citrus nematode in both rootstocks compared with nonmycorrhizal plants. The rate of decrease in nematode infection was highest when plants were pre-inoculated with F. mosseae and was lowest when nematode was inoculated before F. mosseae. However, when nematode was inoculated before the fungus, the fungus was still able to mitigate the negative effect of infection by nematode compared with plants inoculated with nematode only. This suggests that the timing of inoculation plays a crucial role in the effectiveness of F. mosseae in reducing nematode infection. Moreover, monitoring of the expression of two genes, phenylalanine ammonia-lyase and ß-1,3-glucanase, which are involved in systemic-acquired resistance (SAR) showed that although they were significantly upregulated in mycorrhizal plants compared with nonmycorrhizal plants, they showed the highest expression when plants were pretreated with fungus before nematode inoculation, thus, indicating that plants were primed. In summary, F. mosseae primes the defense-related genes involved in SAR, increasing plant defensive capacity and boosting growth parameters in citrus rootstock. This has important implications for the agricultural industry.

Role of chitinase expression in the virulence of Lecanicillium lecanii against citrus black aphid (Toxoptera aurantii).

Chitinase plays a vital role in the virulence of entomopathogenic fungi (EPF) when it infects host insects. We used gene recombination technology to express chitinase of three strains of Lecanicillium lecanii: Vl6063, V3450, and Vp28. The ORF of ChitVl6063, ChitV3450 and ChitVp28 were inserted into the fungal expression vector pBARGPE-1, which contained strong promoter and terminator, respectively, to construct a chitinase overpressing plasmid, then transformed the wild-type strain with blastospore transformation method. The virulence of the three recombinant strains against Toxoptera aurantii was improved by overproduction of ChitVl6063, ChitV3450, and ChitVp28, as demonstrated by significantly lower 3.43 %, 1.72 %, and 1.23 % fatal doses, respectively, according to an insect bioassay. Similarly, lethal times of recombinants (ChitVl6063, ChitV3450 and ChitVp28) were also decreased up to 29.51 %, 30.46 % and 33.90 %, respectively, compared to the wild-type strains. Improving the expression of chitinase is considered as an effective method for the enhancement of the EPF value. The efficacy could be enhanced using recombinant technology, which provides a prospecting view for future insecticidal applications.

QTL analysis on a lemon population provides novel insights on the genetic regulation of the tolerance to the two-spotted spider mite attack.

BACKGROUND: Among the Citrus species, lemon (Citrus limon Burm f.) is one of the most affected by the two-spotted spider mite (Tetranychus urticae Koch). Moreover, chemical control is hampered by the mite's ability to develop genetic resistance against acaricides. In this context, the identification of the genetic basis of the host resistance could represent a sustainable strategy for spider mite control. In the present study, a marker-trait association analysis was performed on a lemon population employing an association mapping approach. An inter-specific full-sib population composed of 109 accessions was phenotyped through a detached-leaf assays performed in modified Huffaker cells. Those individuals, complemented with two inter-specific segregating populations, were genotyped using a target-sequencing approach called SPET (Single Primer Enrichment Technology), the resulting SNPs were employed for the generation of an integrated genetic map. RESULTS: The percentage of damaged area in the full-sib population showed a quantitative distribution with values ranging from 0.36 to 9.67%. A total of 47,298 SNPs were selected for an association mapping study and a significant marker linked with resistance to spider mite was detected on linkage group 5. In silico gene annotation of the QTL interval enabled the detection of 13 genes involved in immune response to biotic and abiotic stress. Gene expression analysis showed an over expression of the gene encoding for the ethylene-responsive transcription factor ERF098-like, already characterized in Arabidopsis and in rice for its involvement in defense response. CONCLUSION: The identification of a molecular marker linked to the resistance to spider mite attack can pave the way for the development of marker-assisted breeding plan for the development of novel selection coupling favorable agronomical traits (e.g. fruit quality, yield) with a higher resistance toward the mite.

Mycorrhiza-induced resistance in citrus against Tetranychus urticae is plant species dependent and inversely correlated to basal immunity.

BACKGROUND: Mycorrhizal plants show enhanced resistance to biotic stresses, but few studies have addressed mycorrhiza-induced resistance (MIR) against biotic challenges in woody plants, particularly citrus. Here we present a comparative study of two citrus species, Citrus aurantium, which is resistant to Tetranychus urticae, and Citrus reshni, which is highly susceptible to T. urticae. Although both mycorrhizal species are protected in locally infested leaves, they show very distinct responses to MIR. RESULTS: Previous studies have indicated that C. aurantium is insensitive to MIR in systemic tissues and MIR-triggered antixenosis. Conversely, C. reshni is highly responsive to MIR which triggers local, systemic and indirect defense, and antixenosis against the pest. Transcriptional, hormonal and inhibition assays in C. reshni indicated the regulation of jasmonic acid (JA)- and abscisic acid-dependent responses in MIR. The phytohormone jasmonic acid isoleucine (JA-Ile) and the JA biosynthesis gene LOX2 are primed at early timepoints. Evidence indicates a metabolic flux from phenylpropanoids to specific flavones that are primed at 24 h post infestation (hpi). MIR also triggers the priming of naringenin in mycorrhizal C. reshni, which shows a strong correlation with several flavones and JA-Ile that over-accumulate in mycorrhizal plants. Treatment with an inhibitor of phenylpropanoid biosynthesis C4H enzyme impaired resistance and reduced the symbiosis, demonstrating that phenylpropanoids and derivatives mediate MIR in C. reshni. CONCLUSION: MIR's effectiveness is inversely correlated to basal immunity in different citrus species, and provides multifaceted protection against T. urticae in susceptible C. reshni, activating rapid local and systemic defenses that are mainly regulated by the accumulation of specific flavones and priming of JA-dependent responses. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Biological Features and In Planta Transcriptomic Analyses of a Microviridae Phage (CLasMV1) in "Candidatus Liberibacter asiaticus".

"Candidatus Liberibacter asiaticus" (CLas) is the causal agent of citrus Huanglongbing (HLB, also called citrus greening disease), a highly destructive disease threatening citrus production worldwide. A novel Microviridae phage (named CLasMV1) has been found to infect CLas, providing a potential therapeutic strategy for CLas/HLB control. However, little is known about the CLasMV1 biology. In this study, we analyzed the population dynamics of CLasMV1 between the insect vector of CLas, the Asian citrus psyllid (ACP, Diaphorina citri Kuwayama) and the holoparasitic dodder plant (Cuscuta campestris Yunck.); both acquired CLasMV1-infected CLas from an HLB citrus. All CLas-positive dodder samples were CLasMV1-positive, whereas only 32% of CLas-positive ACP samples were identified as CLasMV1-positive. Quantitative analyses showed a similar distribution pattern of CLasMV1 phage and CLas among eight citrus cultivars by presenting at highest abundance in the fruit pith and/or the center axis of the fruit. Transcriptome analyses revealed the possible lytic activity of CLasMV1 on CLas in fruit pith as evidenced by high-level expressions of CLasMV1 genes, and CLas genes related to cell wall biogenesis and remodeling to maintain the CLas cell envelope integrity. The up-regulation of CLas genes were involved in restriction-modification system that could involve possible phage resistance for CLas during CLasMV1 infection. In addition, the regulation of CLas genes involved in cell surface components and Sec pathway by CLasMV1 phage could be beneficial for phage infection. This study expanded our knowledge of CLasMV1 phage that will benefit further CLas phage research and HLB control.

Morphological and molecular identification of Cladosporium sphaerospermum isolates collected from tomato plant residues / Identificação morfológica e molecular de isolados de Cladosporium sphaerospermum coletados de resíduos de plantas de tomate

This study was conducted at the Agriculture College University of Karbala, Iraq to isolate and morphologically and molecularly diagnose thirteen Cladosporium isolates collected from tomato plant residues present in desert regions of Najaf and Karbala provinces, Iraq. We diagnosed the obtained isolates by PCR amplification using the ITS1 and ITS4 universal primer pair followed by sequencing. PCR amplification and analysis of nucleotide sequences using the BLAST program showed that all isolated fungi belong to Cladosporium sphaerospermum. Analysis of the nucleotide sequences of the identified C. sphaerospermum isolates 2, 6, 9, and 10 showed a genetic similarity reached 99%, 98%, 99%, and 99%, respectively, with those previously registered at the National Center for Biotechnology Information (NCBl). By comparing the nucleotide sequences of the identified C. sphaerospermum isolates with the sequences belong to the same fungi and available at NCBI, it was revealed that the identified C. sphaerospermum isolates 2, 6, 9, and 10 have a genetic variation with those previously recorded at the National Center for Biotechnology Information (NCBl); therefore, the identified sequences of C. sphaerospermum isolates have been registered in GenBank database (NCBI) under the accession numbers MN896004, MN896107, MN896963, and MN896971, respectively.

Este estudo foi conduzido na Agriculture College University of Karbala, Iraque, para isolar e diagnosticar morfológica e molecularmente treze isolados de Cladosporium coletados de resíduos de plantas de tomate presentes nas regiões desérticas das províncias de Najaf e Karbala, no Iraque. Diagnosticamos os isolados obtidos por amplificação por PCR usando o par de primers universais ITS1 e ITS4 seguido de sequenciamento. A amplificação por PCR e a análise de sequências de nucleotídeos usando o programa BLAST mostraram que todos os fungos isolados pertencem a Cladosporium sphaerospermum. A análise das sequências de nucleotídeos dos isolados 2, 6, 9 e 10 de C. sphaerospermum identificados mostrou similaridade genética de 99%, 98%, 99% e 99%, respectivamente, com aqueles previamente registrados no National Center for Biotechnology Informações (NCBl). Ao comparar as sequências de nucleotídeos dos isolados de C. sphaerospermum identificados com as sequências pertencentes aos mesmos fungos e disponíveis no NCBI, foi revelado que os isolados 2, 6, 9 e 10 de C. sphaerospermum identificados têm variação genética com aqueles anteriormente registrados no National Center for Biotechnology Information (NCBl). Portanto, as sequências identificadas de isolados de C. sphaerospermum foram registradas no banco de dados GenBank (NCBI) sob os números de acesso MN896004, MN896107, MN896963 e MN896971, respectivamente.

Lime sulfur to control citrus flat mite and its interactions with the entomopathogenic fungus Lecanicillium muscarium

Lime sulfur is one of the few products indicated to control Brevipalpus yothersi in Brazilian organic citrus orchards. Other strategies, such as the use of entomopathogenic fungi should be evaluated, and Lecanicillium muscarium is one of the basic choices for pest management. Knowledge of the interactions between lime sulfur and this entomopathogen is critical for developing control strategies. With this goal, it was conducted the toxicological characterization of lime sulfur to B. yothersi and the compatibility evaluation with L. muscarium. Finally, the effects of L. muscarium and lime sulfur mixtures on B. yothersi control were evaluated. Product evaluation for B. yothersi was done through direct and residual contact bioassay, and different concentrations of lime sulfur mixed in potato dextrose agar culture medium were used to evaluate compatibility with L. muscarium. Lime sulfur was effective against adults of B. yothersi and caused eggs unviability of up to 71.0%, at a dose of 80 L per 2,000 L of H2O. The lethal concentration (LC50 and LC99) of lime sulfur estimated for mite adults were 246.62 and 858.5 µg of sulfur per mL of H2O (ppm a.i.). Lime sulfur concentrations of 180 to 560 ppm a.i. showed promise for use in combination with L. muscarium. However, concentrations of 1,000 and 5,600 ppm significantly reduced colony size and the number of spores/colony. The mixture of 100 and 180 ppm a.i. of lime sulfur with L. muscarium (108 conidia·mL­1) was not able to reduce the lethal time of entomopathogen on B. yothersi.

Sublethal effects of bifenazate on biological traits and enzymatic properties in the Panonychus citri (Acari: Tetranychidae).

Panonychus citri, a major citrus pest. In pest management, bifenazate is a novel acaricide with high biological activity against red mites, such as Tetranychus urticae Koch. However, in the field, pests are frequently exposed to sublethal or lethal concentrations of pesticides. At present, its sublethal effects on P. citri have not been reported. Therefore, in order to investigate sublethal effect of bifenazate on biological traits and enzymatic properties of P. citri. The newly emerged females were treated with two concentrations of bifenazate: LC10 and LC30, the development and fecundity were observed. The results showed that female adult duration, fecundity, oviposition days, longevity were decrease compared with control, but pre-oviposition period was longer, net reproductive rate (R0), mean generation (T) were decreased, intrinsic rate of increase (rm), finite rate (λ) were decreased in LC30, however, doubling time was increased. Enzymatic tests showed that CAT, POD, CarE activities were higher in treatments than control. The SOD and GST activities were lower in LC30 than control and LC10, the CYP450 activity was decreased with the increasing concentrations. This study demonstrated that low lethal concentrations of bifenazate adversely affected life table parameters, enzymatic properties in P. citri. Therefore, bifenazate has the potential to control this pest.

Field Experiment Effect on Citrus Spider Mite Panonychus citri of Venom from Jellyfish Nemopilema nomurai: The Potential Use of Jellyfish in Agriculture.

Jellyfish are rich in resources and widely distributed along coastal areas. As a potential approach to respond to jellyfish blooms, the use of jellyfish-derived products is increasing. The citrus spider mite (Panonychus citri) is one of the key citrus pests, negatively impacting the quality and quantity of oranges. Due to the resistance and residue of chemical acaricides, it is important to seek natural substitutes that are environmentally friendly. The field efficacy of the venom from the jellyfish Nemopilema nomurai against P. citri was assayed in a citrus garden. The frozen N. nomurai tentacles were sonicated in different buffers to isolate the venom. The venom isolated by PBS buffer (10 mM, pH 6.0) had the strongest acaricidal activity of the four samples, and the corrected field efficacy 7 days after treatment was up to 95.21%. This study demonstrated that jellyfish has potential use in agriculture.

'Candidatus Xiphinematincola pachtaicus' gen. nov., sp. nov., an endosymbiotic bacterium associated with nematode species of the genus Xiphinema (Nematoda, Longidoridae).

An intracellular bacterium, strain IAST, was observed to infect several species of the plant-parasitic nematode genus Xiphinema (Xiphinema astaregiense, Xiphinema incertum, Xiphinema madeirense, Xiphinema pachtaicum, Xiphinema parapachydermum and Xiphinema vallense). The bacterium could not be recovered on axenic medium. The 16S rRNA gene sequence of IAST was found to be new, being related to the family Burkholderiaceae, class Betaproteobacteria. Fungal endosymbionts Mycoavidus cysteinexigens B1-EBT (92.9 % sequence identity) and 'Candidatus Glomeribacter gigasporarum' BEG34 (89.8 % identity) are the closest taxa and form a separate phylogenetic clade inside Burkholderiaceae. Other genes (atpD, lepA and recA) also separated this species from its closest relatives using a multilocus sequence analysis approach. These genes were obtained using a partial genome of this bacterium. The localization of the bacterium (via light and fluorescence in situ hybridization microscopy) is in the X. pachtaicum females clustered around the developing oocytes, primarily found embedded inside the epithelial wall cells of the ovaries, from where they are dispersed in the intestine. Transmission electron microscopy (TEM) observations supported the presence of bacteria inside the nematode body, where they occupy ovaries and occur inside the intestinal epithelium. Ultrastructural analysis of the bacterium showed cells that appear as mostly irregular, slightly curved rods with rounded ends, 0.8-1.2 µm wide and 2.5-6.0 µm long, possessing a typical Gram-negative cell wall. The peptidoglycan layer is, however, evident only occasionally and not detectable by TEM in most cells. Another irregularly occurring shell surrounding the endosymbiont cells or the cell clusters was also revealed, probably originating from the host cell membrane. Flagella or spore-like cells do not occur and the nucleoid is diffusely distributed throughout the cell. This endosymbiont is transmitted vertically through nematode generations. These results support the proposal of IAST as a new species, although its obligate intracellular and obligate endosymbiont nature prevented isolation of a definitive type strain. Strain IAST is therefore proposed as representing 'Candidatus Xiphinematincola pachtaicus' gen. nov., sp. nov.

Modeling and dynamics of physiological and behavioral resistance of Asian citrus psyllid.

The Asian citrus psyllid (ACP) survival in the presence of contact insecticides may be through physiological adaptations or by behaviorally avoiding. Curiously, although the first alternative is the object of frequent attention, the second was often neglected, but both may lead to insecticide resistance. In this paper, we characterize the growth dynamics of ACP population using a novel impulsive differential equation model to account for the effect of physiological and behavioral resistance, and investigate the threshold conditions for the extinction of ACP population. Furthermore, we discuss the optimal switching methods for insecticides based on two different criteria. Our numerical result suggests that ignoring both resistances or behavioral resistance would underestimate the transmission risk of Huanglongbing, whereas only considering behavioral resistance leads to an overestimation.

Host-specific gene expression as a tool for introduction success in Naupactus parthenogenetic weevils.

Food resource access can mediate establishment success in invasive species, and generalist herbivorous insects are thought to rely on mechanisms of transcriptional plasticity to respond to dietary variation. While asexually reproducing invasives typically have low genetic variation, the twofold reproductive capacity of asexual organisms is a marked advantage for colonization. We studied host-related transcriptional acclimation in parthenogenetic, invasive, and polyphagous weevils: Naupactus cervinus and N. leucoloma. We analyzed patterns of gene expression in three gene categories that can mediate weevil-host plant interactions through identification of suitable host plants, short-term acclimation to host plant defenses, and long-term adaptation to host plant defenses and their pathogens. This approach employed comparative transcriptomic methods to investigate differentially expressed host detection, detoxification, immune defense genes, and pathway-level gene set enrichment. Our results show that weevil gene expression responses can be host plant-specific, and that elements of that response can be maintained in the offspring. Some host plant groups, such as legumes, appear to be more taxing as they elicit a complex gene expression response which is both strong in intensity and specific in identity. However, the weevil response to taxing host plants shares many differentially expressed genes with other stressful situations, such as host plant cultivation conditions and transition to novel host, suggesting that there is an evolutionarily favorable shared gene expression regime for responding to different types of stressful situations. Modulating gene expression in the absence of other avenues for phenotypic adaptation may be an important mechanism of successful colonization for these introduced insects.

Environmental variables influence the developmental stages of the citrus leafminer, infestation level and mined leaves physiological response of Kinnow mandarin.

Climate change has not only exacerbated abiotic stress, but has also rendered external conditions more feasible for pests to spread and infest citrus fruit. Citrus leafminer (Phyllocnistis citrella) is a potential pest that directly feeds the newly sprouted leaves and twigs of all three spring, summer and autumn flushes. Increasing temperatures in spring and autumn, leafminer accrued more heat units or developmental degree days to accelerate the biological stages of its life-cycle, thereby increasing the pressure of infestation. Present work was conducted at three different environmental conditions in Sargodha, Toba Tek Singh (TTS) and Vehari districts of the Punjab province, Pakistan; all three experimental sites were located in different agro-ecological zones. More infestation was recorded in all three flushes at TTS and Vehari than in Sargodha. Overall, more damage was observed due to higher temperatures in TTS and Vehari than in Sargodha. After May-June heat stress, spontaneous vegetative growth continued from July to November, produced newly spouted tender leaves for feeding the leafminer larvae, and was seen more in TTS and Vehari. Leafminer larva prefers to enter young and tender leaves with a maximum entrance in leaves up to 1 cm2 in size while observing no entrance above 3 cm2 of leaf size. Physiological response of leaves primarily attributed to chlorophyll and carotenoid contents, both of which were recorded lower in the mined leaves, thereby reducing leaf photosynthetic activity. Similarly, lower levels of polyphenols and antioxidant activity were also recorded in the mined leaves. The on-tree age of mined leaves of three vegetative flushes of Kinnow plant was also less counted than non-mined leaves. Climate change has affected vegetative phenology and become feasible for pests due to extemporaneous leaf growth, particularly leafminer, and eventually causes economic loss by supplying low carbohydrates either to hanging fruits or next-season crops.

Using micro-computed tomography to reveal the anatomy of adult Diaphorina citri Kuwayama (Insecta: Hemiptera, Liviidae) and how it pierces and feeds within a citrus leaf.

The Asian citrus psyllid (ACP), Diaphorina citri, is a harmful pest of citrus trees that transmits Candidatus Liberibacter spp. which causes Huanglongbing (HLB) (citrus greening disease); this is considered to be the most serious bacterial disease of citrus plants. Here we detail an anatomical study of the external and internal anatomy (excluding the reproductive system) using micro-computed tomography (micro-CT). This is the first complete 3D micro-CT reconstruction of the anatomy of a psylloid insect and includes a 3D reconstruction of an adult feeding on a citrus leaf that can be used on mobile devices. Detailed rendered images and videos support first descriptions of coxal and scapus antennal glands and sexual differences in the internal anatomy (hindgut rectum, mesothoracic ganglion and brain). This represents a significant advance in our knowledge of ACP anatomy, and of psyllids in general. Together the images, videos and 3D model constitute a unique anatomical atlas and are useful tools for future research and as teaching aids.

Comparative proteomics provides insights into diapause program of Bactrocera minax (Diptera: Tephritidae).

The Chinese citrus fly, Bactrocera minax, is a notorious univoltine pest that causes damage to citrus. B. minax enters obligatory pupal diapause in each generation to resist harsh environmental conditions in winter. Despite the enormous efforts that have been made in the past decade, the understanding of pupal diapause of B. minax is currently still fragmentary. In this study, the 20-hydroxyecdysone solution and ethanol solvent was injected into newly-formed pupae to obtain non-diapause- (ND) and diapause-destined (D) pupae, respectively, and a comparative proteomics analysis between ND and D pupae was performed 1 and 15 d after injection. A total of 3,255 proteins were identified, of which 190 and 463 were found to be differentially abundant proteins (DAPs) in ND1 vs D1 and ND15 vs D15 comparisons, respectively. The reliability and accuracy of LFQ method was validated by qRT-PCR. Functional analyses of DAPs, including Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment, and protein-protein interaction (PPI) network construction, were conducted. The results revealed that the diapause program of B. minax is closely associated with several physiological activities, such as phosphorylation, chitin biosynthesis, autophagy, signaling pathways, endocytosis, skeletal muscle formation, protein metabolism, and core metabolic pathways of carbohydrate, amino acid, and lipid conversion. The findings of this study provide insights into diapause program of B. minax and lay a basis for further investigation into its underlying molecular mechanisms.

Complete genome sequence and analysis of Alcaligenes faecalis strain Mc250, a new potential plant bioinoculant.

Here we present and analyze the complete genome of Alcaligenes faecalis strain Mc250 (Mc250), a bacterium isolated from the roots of Mimosa calodendron, an endemic plant growing in ferruginous rupestrian grasslands in Minas Gerais State, Brazil. The genome has 4,159,911 bp and 3,719 predicted protein-coding genes, in a single chromosome. Comparison of the Mc250 genome with 36 other Alcaligenes faecalis genomes revealed that there is considerable gene content variation among these strains, with the core genome representing only 39% of the protein-coding gene repertoire of Mc250. Mc250 encodes a complete denitrification pathway, a network of pathways associated with phenolic compounds degradation, and genes associated with HCN and siderophores synthesis; we also found a repertoire of genes associated with metal internalization and metabolism, sulfate/sulfonate and cysteine metabolism, oxidative stress and DNA repair. These findings reveal the genomic basis for the adaptation of this bacterium to the harsh environmental conditions from where it was isolated. Gene clusters associated with ectoine, terpene, resorcinol, and emulsan biosynthesis that can confer some competitive advantage were also found. Experimental results showed that Mc250 was able to reduce (~60%) the virulence phenotype of the plant pathogen Xanthomonas citri subsp. citri when co-inoculated in Citrus sinensis, and was able to eradicate 98% of juveniles and stabilize the hatching rate of eggs to 4% in two species of agricultural nematodes. These results reveal biotechnological potential for the Mc250 strain and warrant its further investigation as a biocontrol and plant growth-promoting bacterium.

Asian citrus psyllid adults inoculate huanglongbing bacterium more efficiently than nymphs when this bacterium is acquired by early instar nymphs.

The Asian citrus psyllid (Diaphorina citri) transmits the bacterium 'Candidatus Liberibacter asiaticus' (CLas), which causes huanglongbing (citrus greening) disease, in a circulative-propagative manner. We compared CLas inoculation efficiency of D. citri nymphs and adults into healthy (uninfected) citron leaves when both vector stages were reared from eggs on infected plants. The proportion of CLas-positive leaves was 2.5% for nymphs and 36.3% for adults. CLas acquisition by early instar nymphs followed by dissections of adults and 4th instar nymphs revealed that CLas bacterium had moved into the head-thorax section (containing the salivary glands) in 26.7-30.0% of nymphs and 37-45% of adults. Mean Ct values in these sections were 31.6-32.9 and 26.8-27.0 for nymphs and adults, respectively. Therefore, CLas incidence and titer were higher in the head-thorax of adults than in nymphs. Our results suggest that following acquisition of CLas by early instar D. citri nymphs, emerging adults inoculate the bacteria into citrus more efficiently than nymphs because adults are afforded a longer latent period necessary for multiplication and/or translocation of CLas into the salivary glands of the vector. We propose that CLas uses D. citri nymphs mainly for pathogen acquisition and multiplication, and their adults mainly for pathogen inoculation and spread.

Metabolic response of Citrus limon to Asian citrus psyllid infestation revealed by EESI-MS and HPLC.

Asian citrus psyllid (ACP) causes direct and indirect damage to the citrus industry. Extractive electrospray ionization mass spectrometry (EESI-MS) and high performance liquid chromatography (HPLC) were used to detect the metabolites of C. limon leaves at 0, 12, 24, and 72 h after ACP treatment. The EESI-MS results showed that ACP infestation significantly affected metabolites within a short feeding duration with 8 metabolites identified. The metabolites in leaves of these four groups could be distinguished, with 55 peaks showing significant differences including methyl N-methylanthranilate, caffeic acid, and syringic acid. The quantification of 15 phenolic compounds with HPLC-UV method in C. limon leaves after ACP infestation showed that the total content of them reached a peak of 3504.69 µg g-1 at 12 h, with 9 phenolic compounds changing significantly (P < 0.05). A total of 21 metabolites identified in this study were involved in the biosynthesis pathways of flavonoid, flavone and flavonol, isoflavonoid and phenylpropanoid, and the degradation of aminobenzoate. Contents of epicatechin and caffeic acid increased with the feeding time of ACP as detected by both EESI-MS and HPLC. This may be related to plant defense. This study provides novel insights into the biochemical relationship of ACP and its host plants.