Sequencing of RDR6-dependent double-stranded RNAs reveals novel features of plant siRNA biogenesis

Biogenesis of trans-acting siRNAs (tasiRNAs) is initiated by miRNA-directed cleavage of TAS gene transcripts and requires RNA-dependent RNA polymerase 6 (RDR6) and Dicer-like 4 (DCL4). Here, we show that following miR173 cleavage the entire polyadenylated parts of Arabidopsis TAS1a/b/c and TAS2 transcripts are converted by RDR6 to double-stranded (ds)RNAs. Additionally, shorter dsRNAs are produced following a second cleavage directed by a TAS1c-derived siRNA. This tasiRNA and miR173 guide Argonaute 1 complexes to excise the segments from TAS2 and three TAS1 transcripts including TAS1c itself to be converted to dsRNAs, which restricts siRNA production to a region between the two cleavage sites. TAS1c is also feedback regulated by a cis-acting siRNA. We conclude that TAS1c generates a master siRNA that controls a complex network of TAS1/TAS2 siRNA biogenesis and gene regulation. TAS1/TAS2 short dsRNAs produced in this network are processed by DCL4 from both ends in distinct registers, which increases repertoires of tasiRNA

Current State of Natural Foci of Dangerous Infectious Diseases in the Territory of the Russian Federation

Objective of the study is to evaluate the current state of epizootic activity of natural zoonotic foci, as the basis for the development of prophylactic measures aimed at prevention of natural-focal infections during mass events. Materials and methods. Utilized have been reports from the Center of Hygiene and Epidemiology in the Republic of Tatarstan, the data provided by Rospotrebnadzor Administration in the Republic of Tatarstan over the period of 2009-2014, and literature references. Results and conclusions. The most pressing natural-focal infectious diseases are hemorrhagic fever with renal syndrome, tick-borne borreliosis, and tick-borne viral encephalitis. Yersinioses, leptospiroses, and West Nile fever are rarely registered. Tularemia infections have not been reported within the past 20 years. The period of 2009-2013 is characterized by the decrease in the numbers of carriers and vectors of the diseases, as well as epizootic activity of natural foci, which came up to minimum values in 2013. Emerged since 2014 increment in the abundance rates of the carriers and later the vectors can lead to the increase in the incidence of natural-focal diseases. In the territory of the Republic, allocated are the spatial combination areas of natural foci of the diseases of various etiology with high risk of population exposure. Previous to conduction of mass events it is necessary to enhance the epizootiological surveillance in the natural foci, the results of which lay premises for the development of complex prophylactic activities

Severe Wolcott-Rallison syndrome due to a nonsense mutation in the first exon EIF2AK3

Wolcott-Rallison syndrome is a rare autosomal recessive disease characterized by neonatal diabetes mellitus in combination with osteodysplasia and liver failure. This disease is the most common cause of neonatal diabetes mellitus in consanguineous families. Wolcott-Rallison syndrome is associated with mutations in the EIF2AK3, the gene encoding a transmembrane enzyme PERK (pancreatic endoplasmic reticulum kinase) which inhibits the synthesis of proteins in the event of misfolding in the endoplasmic reticulum. In addition to the core symptoms patients may develop multisystemic clinical manifestation including acute renal and liver failure, short stature, exocrine pancreatic insufficiency, neuro-motor deficit, hypothyroidism, anemia, neutropenia, recurrent hypoglycemia. The disease is characterized by high mortality, more than 50% of patients die from fulminant liver failure. The awareness of Wolcott-Rallison syndrome is extremely low due to the rarity of detection, however in view of the severity of the disease and the unfavorable prognosis patients with this syndrome require timely diagnosis and care of well-organized team of specialists

Spectrum of neuro-developmental disorders in children with congenital hyperinsulinism due to activating mutations in GLUD1

BACKGROUND: Hyperinsulinism/hyperammonemia (HI/HA) syndrome is the second most common type of congenital hyperinsulinism caused by an activating GLUD1 mutation. OBJECTIVE: The aim of this study was to determine the clinical profile and long-term neurological outcomes in children with HI/HA syndrome. METHOD: Retrospective review of patients with GLUD1 mutation, treated at two centers in the UK and Russia, over a 15-year period. Different risk factors for neuro-developmental disorders were analyzed by Mann-Whitney U test and Fisher exact p. RESULTS: We identified 25 cases with GLUD1 mutations (12 males). Median age of presentation was 7 months (12 hours-18 months). Hypoglycaemic seizures were the presenting feature in 24 (96%) cases. 24 cases responded to diazoxide and protein restriction whilst one patient underwent partial pancreatectomy. In total, 13 cases (52%) developed neurodevelopmental manifestations. Epilepsy (n=9/25, 36%), learning difficulties (n=8/25, 32%) and speech delay (n=8/25, 32%) were the most common neurological manifestation. Median age of presentation for epilepsy was 12 months with generalized tonic-clonic seizures being the most common (n=4/9, 44.4%) followed by absence seizures (n=3/9, 33.3%). Early age of presentation (p=0.02), diazoxide dose (p=0.04), and a mutation in exon 11 or 12 (p=0.01) was associated with neurological disorder. CONCLUSION: HI/HA syndrome is associated with wide spectrum of neurological disorders. These neurological manifestations were more frequent in cases with mutations affecting the GTP-binding site of GLUD1 in our cohort.The article is available via Open Access. Click on the 'Additional link' above to access the full-text.Published version, accepted versio

Sequencing of RDR6-dependent double-stranded RNAs reveals novel features of plant siRNA biogenesis

Biogenesis of trans-acting siRNAs (tasiRNAs) is initiated by miRNA-directed cleavage of TAS gene transcripts and requires RNA-dependent RNA polymerase 6 (RDR6) and Dicer-like 4 (DCL4). Here, we show that following miR173 cleavage the entire polyadenylated parts of Arabidopsis TAS1a/b/c and TAS2 transcripts are converted by RDR6 to double-stranded (ds)RNAs. Additionally, shorter dsRNAs are produced following a second cleavage directed by a TAS1c-derived siRNA. This tasiRNA and miR173 guide Argonaute 1 complexes to excise the segments from TAS2 and three TAS1 transcripts including TAS1c itself to be converted to dsRNAs, which restricts siRNA production to a region between the two cleavage sites. TAS1c is also feedback regulated by a cis-acting siRNA. We conclude that TAS1c generates a master siRNA that controls a complex network of TAS1/TAS2 siRNA biogenesis and gene regulation. TAS1/TAS2 short dsRNAs produced in this network are processed by DCL4 from both ends in distinct registers, which increases repertoires of tasiRNAs

Primary and secondary siRNAs in geminivirus-induced gene silencing

In plants, RNA silencing-based antiviral defense is mediated by Dicer-like (DCL) proteins producing short interfering (si)RNAs. In Arabidopsis infected with the bipartite circular DNA geminivirus Cabbage leaf curl virus (CaLCuV), four distinct DCLs produce 21, 22 and 24 nt viral siRNAs. Using deep sequencing and blot hybridization, we found that viral siRNAs of each size-class densely cover the entire viral genome sequences in both polarities, but highly abundant siRNAs correspond primarily to the leftward and rightward transcription units. Double-stranded RNA precursors of viral siRNAs can potentially be generated by host RDR-dependent RNA polymerase (RDR). However, genetic evidence revealed that CaLCuV siRNA biogenesis does not require RDR1, RDR2, or RDR6. By contrast, CaLCuV derivatives engineered to target 30 nt sequences of a GFP transgene by primary viral siRNAs trigger RDR6-dependent production of secondary siRNAs. Viral siRNAs targeting upstream of the GFP stop codon induce secondary siRNAs almost exclusively from sequences downstream of the target site. Conversely, viral siRNAs targeting the GFP 3'-untranslated region (UTR) induce secondary siRNAs mostly upstream of the target site. RDR6-dependent siRNA production is not necessary for robust GFP silencing, except when viral siRNAs targeted GFP 5'-UTR. Furthermore, viral siRNAs targeting the transgene enhancer region cause GFP silencing without secondary siRNA production. We conclude that the majority of viral siRNAs accumulating during geminiviral infection are RDR1/2/6-independent primary siRNAs. Double-stranded RNA precursors of these siRNAs are likely generated by bidirectional readthrough transcription of circular viral DNA by RNA polymerase II. Unlike transgenic mRNA, geminiviral mRNAs appear to be poor templates for RDR-dependent production of secondary siRNAs

Clinical and genetic heterogeneity of HNF4A/HNF1A mutations in a multicentre paediatric cohort with hyperinsulinaemic hypoglycaemia

OBJECTIVE: The phenotype mediated by HNF4A/HNF1A mutations is variable and includes diazoxide-responsive hyperinsulinaemic hypoglycaemia (HH) and maturity-onset diabetes of the young (MODY). DESIGN: We characterised an international multicentre paediatric cohort of patients with HNF4Aor HNF1Amutations presenting with HH over a 25-year period (1995-2020). METHODS: Clinical and genetic analysis data from five centres were obtained. Diazoxide responsiveness was defined as the ability to maintain normoglycaemia without intravenous glucose. Macrosomia was defined as a birth weight ≥90th centile. SPSS v.27.1 was used for data analysis. RESULTS: A total of 34 patients (70.6% female, n = 24) with a mean age of 7.1 years (s.d. 6.4) were included. A total of 21 different heterozygous HNF4Amutations were identified in 29 patients (four novels). Four different previously described heterozygous HNF1A mutations were detected in five patients. Most (97.1%, n = 33) developed hypoglycaemia by day 2 of life. The mean birth weight was 3.8 kg (s.d. 0.8), with most infants macrosomic (n = 21, 61.8%). Diazoxide was commenced in 28 patients (82.3%); all responded. HH resolved in 20 patients (58.8%) following a median of 0.9 years (interquartile range (IQR): 0.2-6.8). Nine patients (n = 9, 26.5%) had developmental delay. Two patients developed Fanconi syndrome (p.Arg63Trp, HNF4A) and four had other renal or hepatic findings. Five (14.7%) developed MODY at a median of 11.0 years (IQR: 9.0-13.9). Of patients with inherited mutations (n = 25, 73.5%), a family history of diabetes was present in 22 (88.0%). CONCLUSIONS: We build on the knowledge of the natural history and pancreatic and extra-pancreatic phenotypes of HNF4A/HNF1Amutations and illustrate the heterogeneity of this condition.This article is freely available online. Click on the 'Additional Link' above to access the full-text via the publisher's site.Accepted version, submitted versio

Viral protein suppresses oxidative burst and salicylic acid-dependent autophagy and facilitates bacterial growth on virus-infected plants

Virus interactions with plant silencing and innate immunity pathways can potentially alter the susceptibility of virus-infected plants to secondary infections with nonviral pathogens. We found that Arabidopsis plants infected with Cauliflower mosaic virus (CaMV) or transgenic for CaMV silencing suppressor P6 exhibit increased susceptibility to Pseudomonas syringae pv. tomato (Pst) and allow robust growth of the Pst mutant hrcC-, which cannot deploy effectors to suppress innate immunity. The impaired antibacterial defense correlated with the suppressed oxidative burst, reduced accumulation of the defense hormone salicylic acid (SA) and diminished SA-dependent autophagy. The viral protein domain required for suppression of these plant defense responses is dispensable for silencing suppression but essential for binding and activation of the plant target-of-rapamycin (TOR) kinase which, in its active state, blocks cellular autophagy and promotes CaMV translation. Our findings imply that CaMV P6 is a versatile viral effector suppressing both silencing and innate immunity. P6-mediated suppression of oxidative burst and SA-dependent autophagy may predispose CaMV-infected plants to bacterial infection