scholarly journals Early Population Dynamics of “Candidatus Liberibacter asiaticus” in Susceptible and Resistant Genotypes After Inoculation With Infected Diaphorina citri Feeding on Young Shoots

2021 ◽  
Vol 12 ◽  
Author(s):  
Mônica Neli Alves ◽  
Juan Camilo Cifuentes-Arenas ◽  
Laudecir Lemos Raiol-Junior ◽  
Jesus Aparecido Ferro ◽  
Leandro Peña
Keyword(s):  
Time Course ◽  
Molecular Mechanisms ◽  
Critical Time ◽  
Plant Colonization ◽  
Post Inoculation ◽  
Diaphorina Citri ◽  
Culturable Bacterium ◽  
Whole Plant ◽  
Successful Infection ◽  
Liberibacter Asiaticus

Huanglongbing is a highly destructive citrus disease associated with “Candidatus Liberibacter asiaticus” (Las), a phloem−limited and non-culturable bacterium, naturally transmitted by the psyllid Diaphorina citri. Although diverse approaches have been used to understand the molecular mechanisms involved in the pathogen–host interaction, such approaches have focused on already infected and/or symptomatic plants, missing early events in the initial days post-inoculation. This study aimed to identify the time course of Las multiplication and whole-plant colonization immediately following inoculation by infected psyllids feeding for 2 days. Thus, the experimental approach was to track Las titers after psyllid inoculation in new shoots (NS) of Citrus × sinensis (susceptible), Murraya paniculata (partially resistant), and Bergera koenigii (fully resistant). Soon after psyllid removal, Las titers dropped until the 10–12th days in all three species. Following this, Las titers increased exponentially only in C. × sinensis and M. paniculata, indicating active bacterial multiplication. In C. × sinensis, Las reached a stationary phase at ∼5 log Las cells/g of tissue from the 40th day onward, while in M. paniculata, Las increased at a lower rate of up to ∼3 log Las cells/g of tissue between the 40th and 60th days, decreasing gradually thereafter and becoming undetectable from the 160th day onward. In B. koenigii, Las titers decreased from the start and remained undetectable. In C. × sinensis, an average of 2.6 log of Las cells/g of tissue was necessary for Las to move out of 50% of the NS in 23.6 days and to colonize the rest of the plant, causing a successful infection. Conversely, the probability of Las moving out of the NS remained below 50% in M. paniculata and zero in B. koenigii. To our knowledge, this is the first study on Las dynamics and whole-plant colonization during the earliest stages of infection. Identification of critical time-points for either successful multiplication or Las resistance may help to elucidate initial events of Las–host interactions that may be missed due to longer sampling intervals and at later stages of infection.

Intracellular life cycle of Candidatus Liberibacter asisticus inside psyllid gut cells

2021 ◽  
Author(s):  
Lin Chun-Yi ◽  
Diann Achor ◽  
Amit Levy
Keyword(s):  
Molecular Mechanisms ◽  
Management Strategies ◽  
Bacterial Invasion ◽  
Diaphorina Citri ◽  
Current Management ◽  
Insect Midgut ◽  
Rapid Spread ◽  
Candidatus Liberibacter ◽  
Infected Insect ◽  
Liberibacter Asiaticus

Candidatus Liberibacter asiaticus (CLas), the devastating pathogen related to Huanglongbing (HLB), is a phloem-limited, fastidious, insect-borne bacterium. Rapid spread of HLB disease relies on CLas propagates efficiently in its vector, the Asian citrus psyllid, Diaphorina citri, in a circulative manner. Understanding the intracellular lifecycle of CLas in psyllid midgut is fundamental to improve current management strategies. Using a microscopic approach within CLas-infected insect midgut, we observed the entry of CLas into gut cells inside vesicles by endocytosis, termed Liberibacter containing vacuoles (LCVs). Endocytosis is followed by the formation of endoplasmic reticulum-related and replication permissive vacuoles (rLCVs). rLCVs then further develop into bigger double membrane autophagosome-like structure, termed autophagy-related vacuole (aLCV). Vesicles, containing CLas egress from aLCV and fuse with the cell membrane. Immunolocalization studies showed that CLas employs endo/exocytosis-like mechanisms that mediates bacterial invasion and egress. Upregulation of autophagy-related genes indicated subversion of host autophagy by CLas in psyllid vector to promote infection. These results indicate that CLas interacts with host cellular machineries to undergo a multistage intracellular cycle through endocytic, secretory, autophagic and exocytic pathways via complex machineries. Potential tactics for HLB controlling can be made depending on further investigations on the knowledge of the molecular mechanisms of CLas intracellular cycle.

scholarly journals Diaphorina citri Nymphs Are Resistant to Morphological Changes Induced by “ Candidatus Liberibacter asiaticus” in Midgut Epithelial Cells

2018 ◽  
Vol 86 (4) ◽  
Author(s):  
Marina Mann ◽  
Somayeh Fattah-Hosseini ◽  
El-Desouky Ammar ◽  
Richard Stange ◽  
EricaRose Warrick ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Epithelial Cells ◽  
Molecular Mechanisms ◽  
Early Stage ◽  
Morphological Changes ◽  
Diaphorina Citri ◽  
Content Type ◽  
Citrus Greening Disease ◽  
Mitochondrial Superoxide ◽  
Liberibacter Asiaticus

ABSTRACT “ Candidatus Liberibacter asiaticus” is the causative bacterium associated with citrus greening disease. “ Ca . Liberibacter asiaticus” is transmitted by Diaphorina citri more efficiently when it is acquired by nymphs rather than adults. Why this occurs is not known. We compared midguts of D. citri insects reared on healthy or “ Ca . Liberibacter asiaticus”-infected citrus trees using quantitative PCR, confocal microscopy, and mitochondrial superoxide staining for evidence of oxidative stress. Consistent with its classification as propagative, “ Ca . Liberibacter asiaticus” titers were higher in adults than in nymphs. Our previous work showed that adult D. citri insects have basal levels of karyorrhexis (fragmentation of the nucleus) in midgut epithelial cells, which is increased in severity and frequency in response to “ Ca . Liberibacter asiaticus.” Here, we show that nymphs exhibit lower levels of early-stage karyorrhexis than adults and are refractory to the induction of advanced karyorrhexis by “ Ca . Liberibacter asiaticus” in the midgut epithelium. MitoSox Red staining showed that guts of infected adults, particularly males, experienced oxidative stress in response to “ Ca . Liberibacter asiaticus.” A positive correlation between the titers of “ Ca . Liberibacter asiaticus” and the Wolbachia endosymbiont was observed in adult and nymph midguts, suggesting an interplay between these bacteria during development. We hypothesize that the resistance of the nymph midgut to late-stage karyorrhexis through as yet unknown molecular mechanisms benefits “ Ca . Liberibacter asiaticus” for efficient invasion of midgut epithelial cells, which may be a factor explaining the developmental dependency of “ Ca . Liberibacter asiaticus” acquisition by the vector.

scholarly journals Decoding the temporal nature of brain GR activity in the NFκB signal transition leading to depressive-like behavior

2021 ◽  
Author(s):  
Young-Min Han ◽  
Min Sun Kim ◽  
Juyeong Jo ◽  
Daiha Shin ◽  
Seung-Hae Kwon ◽  
...  
Keyword(s):  
Inhibitory Action ◽  
Time Course ◽  
Molecular Mechanisms ◽  
Late Phase ◽  
Fine Tuning ◽  
Dependent Manner ◽  
Middle Phase ◽  
Temporal Shift

AbstractThe fine-tuning of neuroinflammation is crucial for brain homeostasis as well as its immune response. The transcription factor, nuclear factor-κ-B (NFκB) is a key inflammatory player that is antagonized via anti-inflammatory actions exerted by the glucocorticoid receptor (GR). However, technical limitations have restricted our understanding of how GR is involved in the dynamics of NFκB in vivo. In this study, we used an improved lentiviral-based reporter to elucidate the time course of NFκB and GR activities during behavioral changes from sickness to depression induced by a systemic lipopolysaccharide challenge. The trajectory of NFκB activity established a behavioral basis for the NFκB signal transition involved in three phases, sickness-early-phase, normal-middle-phase, and depressive-like-late-phase. The temporal shift in brain GR activity was differentially involved in the transition of NFκB signals during the normal and depressive-like phases. The middle-phase GR effectively inhibited NFκB in a glucocorticoid-dependent manner, but the late-phase GR had no inhibitory action. Furthermore, we revealed the cryptic role of basal GR activity in the early NFκB signal transition, as evidenced by the fact that blocking GR activity with RU486 led to early depressive-like episodes through the emergence of the brain NFκB activity. These results highlight the inhibitory action of GR on NFκB by the basal and activated hypothalamic-pituitary-adrenal (HPA)-axis during body-to-brain inflammatory spread, providing clues about molecular mechanisms underlying systemic inflammation caused by such as COVID-19 infection, leading to depression.

scholarly journals Expression analysis of defense-related genes in cucumber (Cucumis sativus L.) against Phytophthora melonis

2020 ◽  
Author(s):  
Lida Hashemi ◽  
Ahmad Reza Golparvar ◽  
Mehdi Nasr Esfahani ◽  
Maryam Golabadi
Keyword(s):  
Gene Expression ◽  
Expression Analysis ◽  
Gene Expression Analysis ◽  
Molecular Mechanisms ◽  
Crown Rot ◽  
Economic Losses ◽  
Post Inoculation ◽  
Expression Ratio ◽  
Phytophthora Melonis ◽  
Maximum Expression

AbstractPhytophthora melonis is the causal agent of damping-off or crown rot, one of the most destructive cucumber diseases that causes severe economic losses in Iran and some other parts of the world. Despite intense research efforts made in the past years, no permanent cure currently exists for this disease. With the aim to understand the molecular mechanisms of defense against P. melonis, root collars and leaves of four cucumber genotypes consisting of resistant Ramezz; moderately resistant Baby and very susceptible Mini 6-23 and Extrem, were monitored for quantitative gene expression analysis of five antifungal and/or anti-oomycete genes (CsWRKY20, CsLecRK6.1, PR3, PR1-1a and LOX1) at three points after inoculation with P. melonis. The gene expression analysis indicated that P. melonis strongly enhanced the expression of these genes after inoculation in both leaves and root collars. Further, not only the transcript levels of these genes were significantly higher in the resistant and moderately resistance genotypes, but also the time point of the highest relative expression ratio for the five genes was different in the four cucumber genotypes. CsWRKY20 and PR3 showed the maximum expression in Ramezz at 48 hours post inoculation (hpi) while CsLecRK6.1, and LOX1 showed the highest expression at 72 hpi. In addition, PR1-1a showed the maximum expression in the Baby at 72 hpi. Root collars responded faster than leaves and some responses were more strongly up-regulated in root collars than in leaves. The genes found to be involved in disease resistance in two different organs of cucumber after pathogen infection. The results suggest that increased expression of these genes led to activation of defense pathways and could be responsible for a reduced P. melonis colonization capacity in Ramezz and Baby. Overall, this work represents a valuable resource for future functional genomics studies to unravel the molecular mechanisms of C. sativus- P. melonis interaction.

Probing the application of OmpA-derived peptides to disrupt the acquisition of ‘Candidatus Liberibacter asiaticus’ by Diaphorina citri

2021 ◽  
Author(s):  
Marcus Vinicius Merfa e Silva ◽  
Eduarda Regina Fischer ◽  
Mariana de Souza e Silva ◽  
Carolina Sardinha Francisco ◽  
Helvécio Coletta-Filho ◽  
...  
Keyword(s):  
Control Strategies ◽  
Insect Vector ◽  
Diaphorina Citri ◽  
Candidatus Liberibacter Asiaticus ◽  
In Planta ◽  
Host Interaction ◽  
Vector Population ◽  
Candidatus Liberibacter ◽  
Liberibacter Asiaticus ◽  
Bacterial Outer Membrane

Huanglongbing (HLB) is currently the most devastating disease of citrus worldwide. Both bacteria ‘Candidatus Liberibacter asiaticus’ (CLas) and ‘Ca. Liberibacter americanus’ (CLam) are associated with HLB in Brazil, but with a strong prevalence of CLas over CLam. Conventionally, HLB management focuses on controlling the insect vector population (Diaphorina citri; also known as Asian citrus psyllid – ACP) by spraying insecticides, an approach demonstrated to be mostly ineffective. Thus, development of novel more efficient HLB control strategies is required. The multifunctional bacterial outer membrane protein OmpA is involved in several molecular processes between bacteria and their hosts and has been suggested as a target for bacterial control. Curiously, OmpA is absent in CLam in comparison to CLas, suggesting a possible role on host-interaction. Therefore, in the current study, we have treated ACPs with different OmpA-derived peptides aiming to evaluate the acquisition of CLas by the insect vector. Treatment of psyllids with 5 µM of Pep1, Pep3, Pep5 and Pep6 in artificial diet significantly reduced the acquisition of CLas, while increasing the concentration of Pep5 and Pep6 to 50 µM abolished this process. In addition, in planta treatment with 50 µM of Pep6 also significantly decreased the acquisition of CLas and sweet orange plants stably absorbed and maintained this peptide for as long as three months post the final application. Together, our results demonstrate the promising use of OmpA-derived peptides as a novel biotechnological tool to control CLas.

Sign in / Sign up

Export Citation Format

Share Document