AUXIN RESPONSIVE FACTOR8 regulates development of the feeding site induced by root-knot nematodes in tomato.

Root-knot nematodes (RKN) from the genus Meloidogyne induce the dedifferentiation of root vascular cells into giant multinucleate feeding cells. These feeding cells result from an extensive reprogramming of gene expression, and auxin is known to be a key player in their development. However, little is known about how the auxin signal is transmitted during giant cell development.

Copper microRNAs modulate the formation of giant feeding cells induced by the root knot nematode Meloidogyne incognita in Arabidopsis thaliana.

Root-knot nematodes (RKNs) are root endoparasites that induce the dedifferentiation of a few root cells and the reprogramming of their gene expression to generate giant hypermetabolic feeding cells. We identified two microRNA families, miR408 and miR398, as upregulated in Arabidopsis thaliana and Solanum lycopersicum roots infected by RKNs. In plants, the expression of these two conserved microRNA families is known to be activated by the SPL7 transcription factor in response to copper starvation.

Silencing the conserved small nuclear ribonucleoprotein SmD1 target gene alters susceptibility to root-knot nematodes in plants.

Root-knot nematodes (RKNs) are among the most damaging pests of agricultural crops. Meloidogyne is an extremely polyphagous genus of nematodes that can infect thousands of plant species. A few genes for resistance (R-genes) to RKN suitable for use in crop breeding have been identified, but virulent strains and species of RKN have emerged that render these R-genes ineffective.

The Nuclear Effector MiEFF1 Interacts With Cytosolic Glyceraldehyde-3-Phosphate Dehydrogenases to Promote Parasitism.

Root-knot nematodes are obligate endoparasites that maintain a biotrophic relationship with their hosts over a period of several weeks. They induce the differentiation of root cells into specialized multinucleate hypertrophied feeding cells known as giant cells. Nematode effectors synthesized in the esophageal glands and injected into the plant tissue through the syringe-like stylet play a key role in giant cell ontogenesis.

MicroRNAs, New Players in the Plant-Nematode Interaction.

Plant-parasitic root-knot and cyst nematodes are microscopic worms that cause severe damage to crops and induce major agricultural losses worldwide. These parasites penetrate into host roots and induce the formation of specialized feeding structures, which supply the resources required for nematode development. Root-knot nematodes induce the redifferentiation of five to seven root cells into giant multinucleate feeding cells, whereas cyst nematodes induce the formation of a multinucleate syncytium by targeting a single root cell.

Characterization of siRNAs clusters in Arabidopsis thaliana galls induced by the root-knot nematode Meloidogyne incognita.

Background: Root-knot nematodes (RKN), genus Meloidogyne, are plant parasitic worms that have the ability to transform root vascular cylinder cells into hypertrophied, multinucleate and metabolically over-active feeding cells. Redifferentiation into feeding cells is the result of a massive transcriptional reprogramming of root cells targeted by RKN. Since RKN are able to induce similar feeding cells in roots of thousands of plant species, these worms are thought to manipulate essential and conserved plant molecular pathways.

Hybridization (ISH) in Preparasitic and Parasitic Stages of the Plant-parasitic Nematode spp.

The spatio-temporal expression pattern of a gene provides important indications to better understand its biological function. hybridization (ISH) uses a labeled complementary single-stranded RNA or DNA probe to localize gene transcripts in a whole organism, a whole organ or a section of tissue. We adapted the ISH technique to the plant parasite spp.

Characterization of microRNAs from Arabidopsis galls highlights a role for miR159 in the plant response to the root-knot nematode Meloidogyne incognita.

Root knot nematodes (RKN) are root parasites that induce the genetic reprogramming of vascular cells into giant feeding cells and the development of root galls. MicroRNAs (miRNAs) regulate gene expression during development and plant responses to various stresses. Disruption of post-transcriptional gene silencing in Arabidopsis ago1 or ago2 mutants decrease the infection rate of RKN suggesting a role for this mechanism in the plant-nematode interaction.

Differentially expressed small RNAs in Arabidopsis galls formed by Meloidogyne javanica: a functional role for miR390 and its TAS3-derived tasiRNAs.

Root-knot nematodes (RKNs) induce inside the vascular cylinder the giant cells (GCs) embedded in the galls. The distinctive gene repression in early-developing GCs could be facilitated by small RNAs (sRNA) such as miRNAs, and/or epigenetic mechanisms mediated by 24nt-sRNAs, rasiRNAs and 21-22nt-sRNAs. Therefore, the sRNA-population together with the role of the miR390/TAS3/ARFs module were studied during early gall/GC formation.

Gall-forming root-knot nematodes hijack key plant cellular functions to induce multinucleate and hypertrophied feeding cells.

Among plant-parasitic nematodes, the root-knot nematodes (RKNs) of the Meloidogyne spp. are the most economically important genus. RKN are root parasitic worms able to infect nearly all crop species and have a wide geographic distribution.

New insight into the RNA interference response against cathepsin-L gene in the pea aphid, Acyrthosiphon pisum: molting or gut phenotypes specifically induced by injection or feeding treatments.

RNA interference (RNAi) has been widely and successfully used for gene inactivation in insects, including aphids, where dsRNA administration can be performed either by feeding or microinjection. However, several aspects related to the aphid response to RNAi, as well as the influence of the administration method on tissue response, or the mixed success to observe phenotypes specific to the gene targeted, are still unclear in this insect group. In the present study, we made the first direct comparison of two administration methods (injection or feeding) for delivery of dsRNA targeting the cathepsin-L gene in the pea aphid, Acyrthosiphon pisum.

Neonicotinoid binding, toxicity and expression of nicotinic acetylcholine receptor subunits in the aphid Acyrthosiphon pisum.

Neonicotinoid insecticides act on nicotinic acetylcholine receptor and are particularly effective against sucking pests. They are widely used in crops protection to fight against aphids, which cause severe damage. In the present study we evaluated the susceptibility of the pea aphid Acyrthosiphon pisum to the commonly used neonicotinoid insecticides imidacloprid (IMI), thiamethoxam (TMX) and clothianidin (CLT).

Evolutionary study of duplications of the miRNA machinery in aphids associated with striking rate acceleration and changes in expression profiles.

Background: The sequencing of the genome of the pea aphid Acyrthosiphon pisum revealed an unusual expansion of the miRNA machinery, with two argonaute-1, two dicer-1 and four pasha gene copies. In this report, we have undertaken a deeper evolutionary analysis of the phylogenetic timing of these gene duplications and of the associated selective pressures by sequencing the two copies of ago-1 and dcr-1 in different aphid species of the subfamily Aphidinae. We have also carried out an analysis of the expression of both copies of ago-1 and dcr-1 by semi-quantitative PCR in different morphs of the pea aphid life cycle.

Transcriptomic profiling of the reproductive mode switch in the pea aphid in response to natural autumnal photoperiod.

Aphids are among the rare organisms that can change their reproductive mode across their life cycle. During spring and summer they reproduce clonally and efficiently by parthenogenesis. At the end of summer aphids perceive the shortening of day length which triggers the production of sexual individuals - males and oviparous females - that will mate and lay overwintering cold-resistant eggs.

Sexual and asexual oogenesis require the expression of unique and shared sets of genes in the insect Acyrthosiphon pisum.

Background: Although sexual reproduction is dominant within eukaryotes, asexual reproduction is widespread and has evolved independently as a derived trait in almost all major taxa. How asexuality evolved in sexual organisms is unclear. Aphids, such as Acyrthosiphon pisum, alternate between asexual and sexual reproductive means, as the production of parthenogenetic viviparous females or sexual oviparous females and males varies in response to seasonal photoperiodism.

Bioinformatic prediction, deep sequencing of microRNAs and expression analysis during phenotypic plasticity in the pea aphid, Acyrthosiphon pisum.

Background: Post-transcriptional regulation in eukaryotes can be operated through microRNA (miRNAs) mediated gene silencing. MiRNAs are small (18-25 nucleotides) non-coding RNAs that play crucial role in regulation of gene expression in eukaryotes. In insects, miRNAs have been shown to be involved in multiple mechanisms such as embryonic development, tissue differentiation, metamorphosis or circadian rhythm.

Expansion of the miRNA pathway in the hemipteran insect Acyrthosiphon pisum.

The pathways that allow short noncoding RNAs such as the microRNAs (miRNAs) to mediate gene regulation and control critical cellular and developmental processes involve a limited number of key protein components. These proteins are the Dicer-like RNases, double-stranded RNA (dsRNA)-binding proteins, and the Argonaute (AGO) proteins that process stem-loop hairpin transcripts of endogenous genes to generate miRNAs or long dsRNA precursors (either exogenous or endogenous). Comparative genomics studies of metazoans have shown the pathways to be highly conserved overall; the major difference observed is that the vertebrate pathways overlap in sharing a single Dicer (DCR) and AGO proteins, whereas those of insects appear to be parallel, with distinct Dicers and AGOs required for each pathway.

Cuticular proteins and seasonal photoperiodism in aphids.

For poikilotherm animals such as insects, extreme temperatures can be a severe issue in continental regions. Aphids, which reproduce in spring and summer by viviparity, are prone to death in hard winter conditions. These species exhibit reproductive plasticity adapted to winter by producing oviparous females in autumn, which lay overwintering eggs.

Transcriptomic analysis of intestinal genes following acquisition of pea enation mosaic virus by the pea aphid Acyrthosiphon pisum.

Viruses in the family Luteoviridae are strictly transmitted by aphids in a non-propagative, circulative and persistent mode. Virions ingested by aphids successively cross the gut and the accessory salivary gland epithelia before being released, together with saliva, into the plant vasculature. Virion transport through aphid cells occurs by a transcytosis mechanism.

Shifting from clonal to sexual reproduction in aphids: physiological and developmental aspects.

Developmental biology is one of the fastest growing and fascinating research fields in life sciences. Among the wide range of embryonic development, a fundamental difference exists between organisms with sexual or asexual development. Aphids are unusual organisms which display alternative pathways of sexual and asexual development, the orientation of the pathway being determined by environmental conditions.

Gene knockdown by RNAi in the pea aphid Acyrthosiphon pisum.

Background: RNA interference (RNAi) is a powerful method to inhibit gene expression in a sequence specific manner.

Results: Here, we described the development of RNAi by micro-injection of double-stranded RNA (dsRNA) in the pea aphid Acyrthosiphon pisum. Injection of dsRNA into whole aphid body induced the silencing of two marker genes with different expression patterns: the ubiquitously expressed Ap-crt genes encoding a calreticulin and the gut specific Ap-cath-L gene encoding a cathepsin-L.