Tomato geminivirus encoded RNAi suppressor protein, AC4 interacts with host AGO4 and precludes viral DNA methylation

44 p.-4 fig.-1 tab.Plant RNA silencing systems are organized as a network, regulating plant developmental pathways and restraining invading viruses, by sharing cellular components with overlapping functions. Host regulatory networks operate either at the transcriptional level via RNA-directed DNA methylation, or at the post-transcriptional stage interfering with mRNA to restrict viral infection. However, viral-derived proteins, including suppressors of RNA silencing, favour virus establishment, and also affect plant developmental processes. In this investigation, we report that Tomato leaf curl New Delhi virus-derived AC4 protein suppresses RNA silencing activity and mutational analysis of AC4 showed that Asn-50 in the SKNT-51 motif, in the C-terminal region, is a critical determinant of its RNA silencing suppressor activity. AC4 showed interaction with host AGO4 but not with AGO1, aggregated around the nucleus and influenced cytosine methylation of the viral genome. The possible molecular mechanism by which AC4 interferes in the RNA silencing network, helps virus establishment, and affects plant development is discussed.This work was supported by ICAR-IARI, New Delhi. We are also thankful to Council of Scientific and Industrial Research (CSIR) and Department of Biotechnology, New Delhi for providing fellowship to GK, and VG. The Next Generation BioGreen21 Program (Grant no. PJ011309032017) of the Rural Development Administration, and Grant no. NRF-2016R1D1A1B03930764 from the Korean National Research Foundation, both from the Republic of Korea to P. P. are also acknowledged.Peer reviewe

Not Available

Not AvailablePlant RNA silencing systems are organized as a network, regulating plant developmental pathways and re-straining invading viruses, by sharing cellular components with overlapping functions. Host regulatory networks operate either at the transcriptional level via RNA-directed DNA methylation, or at the post-transcriptional stage interfering with mRNA to restrict viral infection. However, viral-derived proteins, including suppressors of RNAsilencing, favour virus establishment, and also affect plant developmental processes. In this investigation, wereport that Tomato leaf curl New Delhi virus-derived AC4 protein suppresses RNA silencing activity and mu-tational analysis of AC4 showed that Asn-50 in the SKNT-51 motif, in the C-terminal region, is a critical de-terminant of its RNA silencing suppressor activity. AC4 showed interaction with host AGO4 but not with AGO1,aggregated around the nucleus, and influenced cytosine methylation of the viral genome. The possible molecular mechanism by which AC4 interferes in the RNA silencing network, helps virus establishment, and affects plant development is discussed.Not Availabl

Not Available

Not AvailableMain conclusion Tomato leaf curl New Delhi virus-derived AC4 protein interacts with host proteins involved in auxin biosynthesis and reprograms auxin biosynthesis/signaling to help in viral replication and manifestation of the disease-associated symptoms. Abstract Perturbations of phytohormone-mediated gene regulatory network cause growth and developmental defects. Furthermore, plant viral infections cause characteristic disease symptoms similar to hormone-defcient mutants. Tomato leaf curl New Delhi Virus (ToLCNDV)-encoded AC4 is a small protein that attenuates the host transcriptional gene silencing, and aggravated disease severity in tomato is correlated with transcript abundance of AC4. Hence, investigating the role of AC4 in pathogenesis divulged that ToLCNDV-AC4 interacted with host TAR1 (tryptophan amino transferase 1)-like protein, CYP450 monooxygenase—the key enzyme of indole acetic acid (IAA) biosynthesis pathway—and with a protein encoded by senescence-associated gene involved in jasmonic acid pathway. Also, ToLCNDV infection resulted in the upregulation of host miRNAs, viz., miR164, miR167, miR393 and miR319 involved in auxin signaling and leaf morphogenesis concomitant with the decline in endogenous IAA levels. Ectopic overexpression of ToLCNDV-derived AC4 in tomato recapitulated the transcriptomic and disruption of auxin biosynthesis/signaling features of the infected leaves. Furthermore, exogenous foliar application of IAA caused remission of the characteristic disease-related symptoms in tomato. The roles of ToLCNDV-AC4 in reprogramming auxin biosynthesis, signaling and cross-talk with JA pathway to help viral replication and manifest the disease-associated symptoms during ToLCNDV infection are discussed.Not Availabl

Not Available

Not AvailablePerturbations of phytohormone-mediated gene regulatory network cause growth and developmental defects. Furthermore,plant viral infections cause characteristic disease symptoms similar to hormone-deficient mutants. Tomato leafcurl New Delhi Virus (ToLCNDV)-encoded AC4 is a small protein that attenuates the host transcriptional gene silencing, and aggravated disease severity in tomato is correlated with transcript abundance of AC4. Hence, investigating the role of AC4 in pathogenesis divulged that ToLCNDV-AC4 interacted with host TAR1 (tryptophan amino transferase 1)-like protein, CYP450 monooxygenase—the key enzyme of indole acetic acid (IAA) biosynthesis pathway—and with a protein encoded by senescence-associated gene involved in jasmonic acid pathway. Also, ToLCNDV infection resulted in the upregulation of host miRNAs, viz., miR164, miR167, miR393 and miR319 involved in auxin signaling and leaf morphogenesis concomitant with the decline in endogenous IAA levels. Ectopic overexpression of ToLCNDV-derived AC4 in tomato recapitulated the transcriptomic and disruption of auxin biosynthesis/signaling features of the infected leaves. Furthermore, exogenous foliar application of IAA caused remission of the characteristic disease-related symptoms in tomato. The roles of ToLCNDV-AC4 in reprogramming auxin biosynthesis, signaling and cross-talk with JA pathway to help viral replication and manifest the disease-associated symptoms during ToLCNDV infection are discussed.Not Availabl

Not Available

Not AvailablePlant RNA silencing systems are organized as a network, regulating plant developmental pathways and restraining invading viruses, by sharing cellular components with overlapping functions. Host regulatory networks operate either at the transcriptional level via RNA-directed DNA methylation, or at the post-transcriptional stage interfering with mRNA to restrict viral infection. However, viral-derived proteins, including suppressors of RNA silencing, favour virus establishment, and also affect plant developmental processes. In this investigation, we report that Tomato leaf curl New Delhi virus-derived AC4 protein suppresses RNA silencing activity and mutational analysis of AC4 showed that Asn-50 in the SKNT-51 motif, in the C-terminal region, is a critical determinant of its RNA silencing suppressor activity. AC4 showed interaction with host AGO4 but not with AGO1, aggregated around the nucleus, and influenced cytosine methylation of the viral genome. The possible molecular mechanism by which AC4 interferes in the RNA silencing network, helps virus establishment, and affects plant development is discussed.Not Availabl

Immunogenicity of SARS-CoV-2 vaccines BBV152 (COVAXIN®) and ChAdOx1 nCoV-19 (COVISHIELD™) in seronegative and seropositive individuals in India: a multicentre, nonrandomised observational studyResearch in context

Summary: Background: There are limited global data on head-to-head comparisons of vaccine platforms assessing both humoral and cellular immune responses, stratified by pre-vaccination serostatus. The COVID-19 vaccination drive for the Indian population in the age group 18–45 years began in April 2021 when seropositivity rates in the general population were rising due to the delta wave of COVID-19 pandemic during April–May 2021. Methods: Between June 30, 2021, and Jan 28, 2022, we enrolled 691 participants in the age group 18–45 years across four clinical sites in India. In this non-randomised and laboratory blinded study, participants received either two doses of Covaxin® (4 weeks apart) or two doses of Covishield™ (12 weeks apart) as per the national vaccination policy. The primary outcome was the seroconversion rate and the geometric mean titre (GMT) of antibodies against the SARS-CoV-2 spike and nucleocapsid proteins post two doses. The secondary outcome was the frequency of cellular immune responses pre- and post-vaccination. Findings: When compared to pre-vaccination baseline, both vaccines elicited statistically significant seroconversion and binding antibody levels in both seronegative and seropositive individuals. In the per-protocol cohort, Covishield™ elicited higher antibody responses than Covaxin® as measured by seroconversion rate (98.3% vs 74.4%, p < 0.0001 in seronegative individuals; 91.7% vs 66.9%, p < 0.0001 in seropositive individuals) as well as by anti-spike antibody levels against the ancestral strain (GMT 1272.1 vs 75.4 binding antibody units/ml [BAU/ml], p < 0.0001 in seronegative individuals; 2089.07 vs 585.7 BAU/ml, p < 0.0001 in seropositive individuals). As participants at all clinical sites were not recruited at the same time, site-specific immunogenicity was impacted by the timing of vaccination relative to the delta and omicron waves. Surrogate neutralising antibody responses against variants-of-concern including delta and omicron was higher in Covishield™ recipients than in Covaxin® recipients; and in seropositive than in seronegative individuals after both vaccination and asymptomatic infection (omicron variant). T cell responses are reported from only one of the four site cohorts where the vaccination schedule preceded the omicron wave. In seronegative individuals, Covishield™ elicited both CD4+ and CD8+ spike-specific cytokine-producing T cells whereas Covaxin® elicited mainly CD4+ spike-specific T cells. Neither vaccine showed significant post-vaccination expansion of spike-specific T cells in seropositive individuals. Interpretation: Covishield™ elicited immune responses of higher magnitude and breadth than Covaxin® in both seronegative individuals and seropositive individuals, across cohorts representing the pre-vaccination immune history of most of the vaccinated Indian population. Funding: Corporate social responsibility (CSR) funding from Hindustan Unilever Limited (HUL) and Unilever India Pvt. Ltd. (UIPL)