Autophagy plays an important role against pathogen infection in many organisms; however, little has been done with regard to vector-borne plant and animal pathogens, that sometimes replicate and cause deleterious effects in their vectors.
Liberibacter solanacearum (CLso) is a fastidious gram-negative phloem-restricted plant pathogen and vectored by the carrot psyllid,
. The plant disease caused by this bacterium is called carrot yellows and has recently gained much importance due to worldwide excessive economical losses. Here, we demonstrate that calcium ATPase, cytosolic calcium, and most importantly Beclin-1 have a role in regulating autophagy and its association with Liberibacter inside the psyllid. The presence of CLso generates reactive oxygen species and induces the expression of detoxification enzymes in the psyllid midguts, a main site for bacteria transmission. CLso also induces the expression of both sarco/endoplasmic reticulum Ca2+pump (SERCA) and 1,4,5-trisphosphate receptors (ITPR) in midguts, resulting in high levels of calcium in the cellular cytosol. Silencing these genes individually disrupted the calcium levels in the cytosol and resulted in direct effects on autophagy and subsequently on Liberibacter persistence and transmission. Inhibiting Beclin1-phosphorylation through different calcium-induced kinases altered the expression of autophagy and CLso titers and persistence. Based on our results obtained from the midgut, we suggest the existence of a direct correlation between cytosolic calcium levels, autophagy, and CLso persistence and transmission by the carrot psyllid.
Plant diseases caused by vector-borne Liberibacter species are responsible for the most important economic losses in many agricultural sectors. Preventing these diseases relies mostly on chemical sprays against the insect vectors. Knowledge-based interference with the bacteria-vector interaction remains a promising approach as a sustainable solution. For unravelling how Liberibacter exploits molecular pathways in its insect vector for transmission, here, we show that the bacterium manipulates calcium levels on both sides of the endoplasmic reticulum membrane, resulting in manipulating autophagy. Silencing genes associated with these pathways disrupted the calcium levels in the cytosol and resulted in direct effects on autophagy and Liberibacter transmission. These results demonstrate major pathways that could be exploited for manipulating and controlling the disease transmission.
Bacterial cells can vary greatly in size, from a few hundred nanometers to hundreds of micrometers in diameter. Filamentous cable bacteria also display substantial size differences, with filament diameters ranging from 0.4 to 8 µm. We analyzed the genomes of cable bacterium filaments from 11 coastal environments of which the resulting 23 new genomes represent 10 novel species-level clades of
Electrothrix and two clades that putatively represent novel genus-level diversity. Fluorescence
hybridization with a species-level probe showed that large-sized cable bacteria belong to a novel species with the proposed name
. Electrothrix gigas. Comparative genome analysis suggests genes that play a role in the construction or functioning of large cable bacteria cells: the genomes of
. Electrothrix gigas encode a novel actin-like protein as well as a species-specific gene cluster encoding four putative pilin proteins and a putative type II secretion platform protein, which are not present in other cable bacteria. The novel actin-like protein was also found in a number of other giant bacteria, suggesting there could be a genetic basis for large cell size. This actin-like protein (denoted big bacteria protein, Bbp) may have a function analogous to other actin proteins in cell structure or intracellular transport. We contend that Bbp may help overcome the challenges of diffusion limitation and/or morphological complexity presented by the large cells of
. Electrothrix gigas and other giant bacteria.
In this study, we substantially expand the known diversity of marine cable bacteria and describe cable bacteria with a large diameter as a novel species with the proposed name
Electrothrix gigas. In the genomes of this species, we identified a gene that encodes a novel actin-like protein [denoted big bacteria protein (Bbp)]. The
gene was also found in a number of other giant bacteria, predominantly affiliated to Desulfobacterota and Gammaproteobacteria, indicating that there may be a genetic basis for large cell size. Thus far, mostly structural adaptations of giant bacteria, vacuoles, and other inclusions or organelles have been observed, which are employed to overcome nutrient diffusion limitation in their environment. In analogy to other actin proteins, Bbp could fulfill a structural role in the cell or potentially facilitate intracellular transport.
Citrus Huanglongbing (HLB), also called citrus greening disease, is a highly destructive disease threatening citrus production worldwide. “
Liberibacter asiaticus” is one of the most common putative causal agents of HLB. Phages of “
. Liberibacter asiaticus”
The Asian citrus psyllid (ACP) is an important vector of the HLB pathogen, which is a major threat to citrus production around the world. Bacterial communities harbored by insects could be affected by different environmental factors.
The hypervariable genomic regions derived from 35 published
Las genomes were used to decipher the genetic diversity of
Las strains and identify 10 new strains with high variations in prophage regions. Characterizing these variations in the
Las bacteria might provide insight into their evolution and adaptation to host plants and insects in China.
Methanogens are important hydrogen consumers in the gut and are associated with differing host health. Here, we determine the prevalence and abundance of archaeal species in the guts of a multi-ethnic cohort of healthy Singapore residents.