Entry into Midgut Epithelial Cells is a Key Step in the Selection of Genotypes in a Nucleopolyhedrovirus

An isolate of the Spodoptera frugiperda multiple nucleopolyhedrovirus comprises a stable proportion of deletion genotypes （e.g., SfNIC-C）, that lack pifl and pif2 rendering them noninfectious per os, and that survive by complementation with a complete genotype （SfNIC-B） in coinfected cells. To determine whether selection for particular ratios of complete and deletion genotypes occurs mainly during the establishment of the primary infection in insect midgut cells or during subsequent systemic infection, we examined genotype frequencies in insects that fed on OBs comprising different co-occluded mixtures of genotypes. Dramatic changes in genotype frequencies were observed between the OB inoculum and budded virus （BV） samples taken from larvae inoculated with OBs comprising 10% SfNIC-B ＋ 90% SfNIC-C indicating that a marked reduction of SfNIC-C genotype had occurred in the insect midgut due to the immediate elimination of all OBs that originated from cells that had been infected only by SfNIC-C. In contrast, immediate changes were not observed in OBs comprising mixtures of 50% SfNIC-B ＋ 50% SfNIC-C or those comprising 10% SfNIC-B ＋ 90% SfNIC-C as most of the OBs in these mixtures originated from cells that had been infected by both genotypes. Subsequent changes in genotypic frequencies during five days of systemic infection were fairly small in magnitude for all genotypic mixtures. We conclude that the prevalence of defective genotypes in the SfNIC population is likely determined by a balance between host selection against OBs produced in cells infected by SfNIC-C alone and within-host selection for fast-replicating deletion genotypes. The strength of intra-host selection is likely modulated by changes in MOI during the infection period.

Multiscale assessment of ground,aerial and satellite spectral data for monitoring wheat grain nitrogen content

Wheat grain quality characteristics have experienced increasing attention as a central factor affecting wheat end-use products quality and human health.Nonetheless,in the last decades a reduction in grain quality has been observed.Therefore,it is central to develop efficient quality-related phenotyping tools.In this sense,one of the most relevant wheat features related to grain quality traits is grain nitrogen content,which is directly linked to grain protein content and monitorable with remote sensing approaches.Moreover,the relation between nitrogen fertilization and grain nitrogen content(protein)plays a central role in the sustainability of agriculture.Both aiming to develop efficient phenotyping tools using remote sensing instruments and to advance towards a field-level efficient and sustainable monitoring of grain nitrogen status,this paper studies the efficacy of various sensors,multispectral and visible red-greenblue(RGB),at different scales,ground and unmanned aerial vehicle(UAV),and phenological stages(anthesis and grain filling)to estimate grain nitrogen content.Linear models were calculated using vegetation indices at each sensing level,sensor type and phenological stage.Furthermore,this study explores the up-scalability of the best performing model to satellite level Sentinel-2 equivalent data.We found that models built at the phenological stage of anthesis with UAV-level multispectral cameras using red-edge bands outperformed grain nitrogen content estimation(R2=0.42,RMSE=0.18%)in comparison with those models built with RGB imagery at ground and aerial level,as well as with those built with widely used ground-level multispectral sensors.We also demonstrated the possibility to use UAV-built multispectral linear models at the satellite scale to determine grain nitrogen content effectively(R2=0.40,RMSE=0.29%)at actual wheat fields.

The lncRNA APOLO interacts with the transcription factor WRKY42 to trigger root hair cell expansion in response to cold

Plant long noncoding RNAs(lncRNAs)have emerged as important regulators of chromatin dynamics,impacting on transcriptional programs leading to different developmental outputs.The lncRNA AUXIN-REGULATED PROMOTER LOOP(APOLO)directly recognizes multiple independent loci across the Arabidopsis genome and modulates their three-dimensional chromatin conformation,leading to transcriptional shifts.Here,we show that APOLO recognizes the locus encoding the root hair(RH)master regulator ROOT HAIR DEFECTIVE 6(RHD6)and controls RHD6 transcriptional activity,leading to cold-enhanced RH elongation through the consequent activation of the transcription factor gene RHD6-like RSL4.Furthermore,we demonstrate that APOLO interacts with the transcription factor WRKY42 and modulates its binding to the RHD6 promoter.WRKY42 is required for the activation of RHD6 by low temperatures and WRKY42 deregulation impairs cold-induced RH expansion.Collectively,our results indicate that a novel ribonucleoprotein complex with APOLO and WRKY42 forms a regulatory hub to activate RHD6 by shaping its epigenetic environment and integrate signals governing RH growth and development.

HASTY modulates miRNA biogenesis by linking pri-miRNA transcription and processing

Post-transcriptional gene silencing mediated by microRNAs(miRNAs)modulates numerous developmental and stress response pathways.For the last two decades,HASTY(HST),the ortholog of human EXPORTIN 5,was considered to be a candidate protein that exports plant miRNAs from the nucleus to the cytoplasm.Here,we report that HST functions in the miRNA pathway independent of its cargo-exporting activity in Arabidopsis.We found that Arabidopsis mutants with impaired HST shuttling exhibit normal subcellular distribution of miRNAs.Interestingly,protein-protein interaction and microscopy assays showed that HST directly interacts with the microprocessor core component DCL1 through its N-terminal domain.Moreover,mass spectrometry analysis revealed that HST also interacts independently of its N-terminal domain with the mediator complex subunit MED37.Further experiments revealed that HST could act as a scaffold to facilitate the recruitment of DCL1 to genomic MIRNA loci by stabilizing the DCL1-MED37 complex,which in turn promotes the transcription and proper processing of primary miRNA transcripts(primiRNAs).Taken together,these results suggest that HST is likely associated with the formation of the miRNA biogenesis complex at MIRNA genes,promoting the transcription and processing of primiRNAs rather than the direct export of processed miRNAs from the nucleus.

The lncRNA MARS modulates the epigenetic reprogramming of the marneral cluster in response to ABA

Clustered organization of biosynthetic non-homologous genes is emerging as a characteristic feature of plant genomes.The co-regulation of clustered genes seems to largely depend on epigenetic reprogram-ming and three-dimensional chromatin conformation.In this study,we identified the long non-coding RNA(lncRNA)MARneral Silencing(MARS),localized inside the Arabidopsis marneral cluster,which con-trols the local epigenetic activation of its surrounding region in response to abscisic acid(ABA).MARS modulates the POLYCOMB REPRESSIVE COMPLEX 1(PRC1)component LIKE HETEROCHROMATIN PROTEIN 1(LHP1)binding throughout the cluster in a dose-dependent manner,determining H3K27me3 deposition and chromatin condensation.In response to ABA,MARS decoys LHP1 away from the cluster and promotes the formation of a chromatin loop bringing together the MARNERAL SYNTHASE 1(MRN1)locus and a distal ABA-responsive enhancer.The enrichment of co-regulated lncRNAs in clustered meta-bolic genes in Arabidopsis suggests that the acquisition of novel non-coding transcriptional units may constitute an additional regulatory layer driving the evolution of biosynthetic pathways.