Auxin drives tomato spotted wilt virus (TSWV) resistance through epigenetic regulation of auxin response factor ARF8 expression in tomato

[EN] Tomato spotted wilt virus (TSWV) causes severe losses of tomato crops worldwide. To cope dynamically with such a threat, plants deploy strategies acting at the molecular and the epigenetic levels. We found that tomato symptoms progress in a specific-genotype-manner upon TSWV infection. Susceptible genotypes showed within the Auxin Response Factor (ARF8) promoter coupled to enhanced expression of miRNA167a, reduced ARF8 gene and decreased levels of the hormone auxin. This constitutes a deliberate attempt of TSWV to disrupt plant growth to promote spread in sensitive cultivars. Epigenetic regulation through the level of cytosine methylation and the miR167a-ARF8 module are part of a complex network modulating auxin-triggered synthesis and shaping tomato responses to TSWV. Furthermore, modulation of miR167a-ARF8 regulatory module could be applied in tomato-resistance breeding programsThis work was financially supported by the Ministry of Higher Education and Scientific Research of TunisiaWerghi, S.; Aparicio Herrero, F.; Fakhfakh, H.; Gorsane, F. (2021). Auxin drives tomato spotted wilt virus (TSWV) resistance through epigenetic regulation of auxin response factor ARF8 expression in tomato. Gene. 804:1-10. https://doi.org/10.1016/j.gene.2021.145905S11080

Molecular detection and characterization of <i>Hop stunt viroid</i> sequence variants from naturally infected pomegranate (<i>Punica granatum </i>L.) in Tunisia

Tunisian pomegranate Hop stunt viroid (HSVd) variants are described. Dot-blot hybridization, S-Page, and reverse transcription polymerase chain reaction (RT-PCR) of RNA extracts from infected tissues were carried out. Results obtained by these techniques were confirmed by cDNA sequencing. The genetic diversity among the Tunisian variants was investigated, which also involved analysis of sequences of previously described HSVd variants from Tunisian citrus var. clementine and fig, and from fruit trees from other Mediterranean countries. Phylogenetic analysis showed that Tunisian pomegranate HSVd variants were clustered into two groups: a cachexia strain within the citrus type group and a recombinant citrus-plum type group. Results also showed a high haplotype diversity which was not related either to the host or to the geographical origin. Selective neutrality and genetic network tests suggest that the HSVd isolates have spread rapidly

Insights into the function of the chloroplastic ribosome-associated GTPase HflX in<i>Arabidopsis thaliana</i>

Ribosome-associated GTPases are conserved enzymes that participate in ribosome biogenesis and ribosome function. In bacteria, recent studies have identified HflX as a ribosome-associated GTPase that is involved in both ribosome biogenesis and recycling under stress conditions. Plants possess a chloroplastic HflX homolog, but its function remains unknown. Here, we characterised the role of HflX in the plant Arabidopsis thaliana. Our findings demonstrate that HflX does not have a detectable role in plant growth and development, nor does it play a distinct role in acclimation to several different stresses, including heat, manganese, cold, and salt stress. However, we found that HflX is required for plant resistance to chloroplast translational stress mediated by the antibiotic lincomycin. Our results suggest that HflX is a chloroplast ribosomeassociated protein that may play a role in the surveillance of translation. These findings provide new insight into the function of HflX as a ribosome-associated GTPase in plants and highlight the importance of investigating conserved proteins in different organisms to gain a comprehensive understanding of their biological roles

Insights into the function of the chloroplastic ribosome‐associated GTPase high frequency of lysogenization X in Arabidopsis thaliana

Abstract Ribosome‐associated GTPases are conserved enzymes that participate in ribosome biogenesis and ribosome function. In bacteria, recent studies have identified HflX as a ribosome‐associated GTPase that is involved in both ribosome biogenesis and recycling under stress conditions. Plants possess a chloroplastic HflX homolog, but its function remains unknown. Here, we characterized the role of HflX in the plant Arabidopsis thaliana. Our findings show that HflX does not affect normal plant growth, nor does it play an essential role in acclimation to several different stresses, including heat, manganese, cold, and salt stress under the conditions tested. However, we found that HflX is required for plant resistance to chloroplast translational stress mediated by the antibiotic lincomycin. Our results suggest that HflX is a chloroplast ribosome‐associated protein that may play a role in the surveillance of translation. These findings provide new insight into the function of HflX as a ribosome‐associated GTPase in plants and highlight the importance of investigating conserved proteins in different organisms to gain a comprehensive understanding of their biological roles

Molecular detection and characterization of Hop stunt viroid sequence variants from naturally infected pomegranate (Punica granatum L.) in Tunisia

Tunisian pomegranate Hop stunt viroid (HSVd) variants are described. Dot-blot hybridization, S-Page, and reverse transcription polymerase chain reaction (RT-PCR) of RNA extracts from infected tissues were carried out. Results obtained by these techniques were confirmed by cDNA sequencing. The genetic diversity among the Tunisian variants was investigated, which also involved analysis of sequences of previously described HSVd variants from Tunisian citrus var. clementine and fig, and from fruit trees from other Mediterranean countries. Phylogenetic analysis showed that Tunisian pomegranate HSVd variants were clustered into two groups: a cachexia strain within the citrus type group and a recombinant citrus-plum type group. Results also showed a high haplotype diversity which was not related either to the host or to the geographical origin. Selective neutrality and genetic network tests suggest that the HSVd isolates have spread rapidly

A landscape genetic analysis of important agricultural pest species in Tunisia: The whitefly Bemisia tabaci.

Combining landscape ecology and genetics provides an excellent framework to appreciate pest population dynamics and dispersal. The genetic architectures of many species are always shaped by environmental constraints. Because little is known about the ecological and genetic traits of Tunisian whitefly populations, the main objective of this work is to highlight patterns of biodiversity, genetic structure and migration routes of this pest. We used nuclear microsatellite loci to analyze B. tabaci populations collected from various agricultural areas across the country and we determine their biotype status. Molecular data were subsequently interpreted in an ecological context supplied from a species distribution model to infer habitat suitability and hereafter the potential connection paths between sampling localities. An analysis of landscape resistance to B. tabaci genetic flow was thus applied to take into account habitat suitability, genetic relatedness and functional connectivity of habitats within a varied landscape matrix. We shed light on the occurrence of three geographically delineated genetic groups with high levels of genetic differentiation within each of them. Potential migration corridors of this pest were then established providing significant advances toward the understanding of genetic features and the dynamic dispersal of this pest. This study supports the hypothesis of a long-distance dispersal of B. tabaci followed by infrequent long-term isolations. The Inference of population sources and colonization routes is critical for the design and implementation of accurate management strategies against this pest

Genetic diversity parameters calculated for tested microsatellite loci.

<p>Genetic diversity parameters calculated for tested microsatellite loci.</p

A landscape genetic analysis of important agricultural pest species in Tunisia: The whitefly <i>Bemisia tabaci</i> - Fig 4

<p>(a) Gaussian kernel density estimates of annual mean temperature values within occurrence data. Red lines represent the result of 1000 permutations based on random samples of the initial occurrence data (70%). (b) Annual mean temperature map. (c) Development rate and (d) survival rate curves as a function of temperature (in°C) for immature and adult whiteflies estimated by [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0185724#pone.0185724.ref007" target="_blank">7</a>].</p

Multiple co-inertia analysis (MCOA) analysis.

<p>Single markers coordinated for the first two axes of the PCA. Corresponding plots are drawn on the same scale for the seven markers involved. The first two axes of the % PCA are shown. The three groups of populations are labeled within confidence ellipses (P = 0.95), with an envelope formed by the most discriminating alleles that are joined by lines. The shown barplot of Eigen-values indicates the relative magnitude of each axis with respect to total variance. Distribution of groups based on the common congruence values (Cos²) for the two components of the first axis.</p

Collections’ details for the 59 samples of <i>Bemisia tabaci</i> from Tunisia.

<p>Collections’ details for the 59 samples of <i>Bemisia tabaci</i> from Tunisia.</p