Sl-IAA27 gene expression is induced during arbuscular mycorrhizal symbiosis in tomato and in Medicago truncatula

Aux/IAA genes play a pivotal role in auxin transcriptional regulation. Their functions were mainly studied in Arabidopsis through analysis of gain-of-function mutants. In the tomato, the Solanaceae reference species, different studies on Sl-IAA down-regulated lines showed specific role for Sl-IAA genes. Our recent work revealed that the Sl-IAA 27 gene displays a distinct behavior compared with most Aux/IAA genes, being down-regulated by auxin. Interestingly, the silencing of Sl-IAA27 leads to altered chlorophyll accumulation in leaves, reduced fertilization, altered fruit development and altered root formation. Here we report that IAA27 could be a key auxin signaling gene involved in AM in tomato and also in Medicago model plant. Indeed both Sl-IAA27 and its closest homolog in Medicago truncatula, Mt-IAA27, are overexpressed in mycorrhized roots. These data are in line with the putative role of auxin in arbuscular mycorrhization

Sl-IAA27 regulates strigolactone biosynthesis and mycorrhization in tomato (var. MicroTom)

- Root colonization by arbuscular mycorrhizal (AM) fungi is a complex and finely tuned process. Previous studies have shown that, among other plant hormones, auxin plays a role in this process but the specific involvement of Aux/IAAs, the key regulators of auxin responses, is still unknown. -In this study, we addressed the role of the tomato Sl-IAA27 during AM symbiosis by using Sl-IAA27-RNAi and pSL-IAA27::GUS stable tomato lines. - The data show that Sl-IAA27 expression is up-regulated by the AM fungus and that silencing of Sl-IAA27 has a negative impact on AM colonization. Sl-IAA27-silencing resulted in down-regulation of three genes involved in strigolactone synthesis, NSP1, D27 and MAX1, and treatment of Sl-IAA27-silenced plants with the strigolactone analog GR24 complemented their mycorrhizal defect phenotype. - Overall, the study identified an Aux/IAA gene as a new component of the signaling pathway controlling AM fungal colonization in tomato. This gene is proposed to control strigolactone biosynthesis via the regulation of NSP1

A Comparison of TSV Etch Metrology Techniques

International audienceWe use three metrology techniques, vertical scanning interferometry (VSI), confocal chromatic microscopy (CCM), and time domain optical coherence tomography (TD-OCT), for depth measurement of through-silicon vias (TSVs) of various cross sections and depths. The merits of these techniques are discussed and compared. Introduction While sales of semiconductor equipment broke a new record this year, many metrology needs should be addressed to support the development and production of electronic chips based on "More than Moore" scaling. Among these scaling approaches, 3D integration based on TSVs offers superior integration density and reduces interconnect length/latency. Measurements are needed to evaluate the depth uniformity of etched TSVs. Indeed, upon metal filling, geometrical variations of TSVs can affect Cu nails coplanarity and can warp the wafer, resulting in a low stacking yield. Measuring the depth of TSVs is an increasingly challenging task as the diameter of many TSVs has now shrunk to only a few microns

Auxin Perception Is Required for Arbuscule Development in Arbuscular Mycorrhizal Symbiosis

Most land plant species live in symbiosis with arbuscular mycorrhizal fungi. These fungi differentiate essential functional structures called arbuscules in root cortical cells from which mineral nutrients are released to the plant. We investigated the role of microRNA393 (miR393), an miRNA that targets several auxin receptors, in arbuscular mycorrhizal root colonization. Expression of the precursors of the miR393 was down-regulated during mycorrhization in three different plant species: Solanum lycopersicum, Medicago truncatula, and Oryza sativa. Treatment of S. lycopersicum, M. truncatula, and O. sativa roots with concentrations of synthetic auxin analogs that did not affect root development stimulated mycorrhization, particularly arbuscule formation. DR5-GUS, a reporter for auxin response, was preferentially expressed in root cells containing arbuscules. Finally, overexpression of miR393 in root tissues resulted in down-regulation of auxin receptor genes (transport inhibitor response1 and auxin-related F box) and underdeveloped arbuscules in all three plant species. These results support the conclusion that miR393 is a negative regulator of arbuscule formation by hampering auxin perception in arbuscule-containing cells

Plant microRNAs: key regulators of root architecture and biotic interactions

International audiencePlants have evolved a remarkable faculty of adaptation to deal with various and changing environmental conditions. In this context, the roots have taken over nutritional aspects and the root system architecture can be modulated in response to nutrient availability or biotic interactions with soil microorganisms. This adaptability requires a fine tuning of gene expression. Indeed, root specification and development are highly complex processes requiring gene regulatory networks involved in hormonal regulations and cell identity. Among the different molecular partners governing root development, microRNAs (miRNAs) are key players for the fast regulation of gene expression. miRNAs are small RNAs involved in most developmental processes and are required for the normal growth of organisms, by the negative regulation of key genes, such as transcription factors and hormone receptors. Here, we review the known roles of miRNAs in root specification and development, from the embryonic roots to the establishment of root symbioses, highlighting the major roles of miRNAs in these processes

Identification de gènes fongiques indispensables à l'établissement de la symbiose ectomycorhizienne

La majorité des plantes supérieures établissent des symbioses mycorhiziennes avec des champignons qui colonisent leurs racines. Ces symbioses améliorent la nutrition hydrique et minérale des plantes et fournissent aux champignons les hydrates de carbone nécessaires à leur croissance. Le but de ma thèse a été d'identifier des gènes fongiques indispensables à l'établissement de cette symbiose. Une collection de 4000 mutants insertionnels du champignon Hebeloma cylindrosporum a été obtenue et criblée en vue d'identifier des mutants non ou faiblement mycorhiziens. Je me suis focalisé sur deux mutants faiblement mycorhiziens. Dans les 2 cas j'ai identifié le gène inactivé. Après avoir cloné l'allèle sauvage de chacun de ces gènes, j'ai étudié leur expression dans des mycéliums en culture pure et en symbiose avec le pin maritimeLYON1-BU.Sciences (692662101) / SudocSudocFranceF

NIN Is Involved in the Regulation of Arbuscular Mycorrhizal Symbiosis

Arbuscular mycorrhizal (AM) symbiosis is an intimate and ancient symbiosis found between most of terrestrial plants and fungi from the Glomeromycota family. Later during evolution, the establishment of the nodulation between legume plants and soil bacteria known as rhizobia, involved several genes of the signalling pathway previously implicated for AM symbiosis. For the past years, the identification of the genes belonging to this Common Symbiotic Signalling Pathway have been mostly done on nodulation. Among the different genes already well identified as required for nodulation, we focused our attention on the involvement of Nodule Inception (NIN) in AM symbiosis. We show here that NIN expression is induced during AM symbiosis, and that the Medicago truncatula nin mutant is less colonized than the wild type M. truncatula strain. Moreover, nin mutant displays a defect in the ability to be infected by the fungus Rhizophagus irregularis. This work brings a new evidence of the common genes involved in overlapping signalling pathways of both nodulation and in AM symbiosis

A fungal conserved gene from the basidiomycete Hebeloma cylindrosporum is essential for efficient ectomycorrhiza formation

International audienceWe used Agrobacterium-mediate insertional mutagenesis to identify genes in the ectomycorrhizal fungus Hebeloma cylindrosporum that are essential for efficient mycorrhiza formation. One of the mutants presented a dramatically reduced ability to form ectomycorrhizas when grown in the presence of Pinus pinaster. It failed to form mycorrhizas in the presence of 0.5 g l-1 glucose, a condition favourable for mycorrhiza formation by the wild-type strain. It however formed few mycorrhizas when glucose was replaced by fructose or when glucose concentration was increased to 1 g l-1. Scanning electron microscopy examination of these mycorrhizas revealed that this mutant was unable to differentiate true fungal sheath and Hartig net. Molecular analyses showed that the single-copy disrupting T-DNA was integrated 6884 bp downstream the start codon, of an ORF potentially encoding a 3096 amino acid-long protein. This gene, which we named HcMycE1 has orthologs in numerous fungi as well as different other eukaryotic microorganisms. RNAi inactivation of HcMycE1 in wild-type strain also led to a mycorrhizal defect, demonstrating that the non-mycorrhizal phenotype of the mutant was due to mutagenic T-DNA integration in HcMycE1. In the wild-type strain colonizing P. pinaster roots, HcMycE1 was transiently up-regulated before symbiotic structures differentiation. Together with the inability of the mutant to differentiate these structures, this suggests that HcMycE1 plays a crucial role upstream fungal sheath and Hartig net differentiation. This study provides the first characterization of a fungal mutant altered in mycorrhizal ability