Biology subjects

Auriac, M.-C.

Publications and source records attributed to Auriac, M.-C..

5 recordsLinked to original sources

bioRxiv2026

An infection assay recapitulating Xanthomonas translucens pv. translucens natural entry into barley hydathodes

Pathogenic bacteria navigate biological host landscapes to enter and establish infection. How Xanthomonas phytopathogenic bacteria enter specific plant tissues is believed to directly determine the systemic vs. local outcome of infection. Non-vascular Xanthomonas infect leaf mesophyll locally from stomatal pores, while vascular ones enter through hydathode water pores on the leaf margin before invading the xylem for systemic movement. The pathovar Xanthomonas translucens pv. translucens (Xtt) is associated with barley infection, causing both bacterial leaf streak and bacterial blight symptoms by colonizing both the mesophyll spaces through stomatal guard cells and the plant vasculature, respectively. How Xtt reaches the vasculature in barley leaves is yet to be established. In this study, we determined the anatomy of barley hydathodes. A protocol allowing efficient hydathode infection by Xtt was established and caused bacterial blight symptoms, closely mimicking the natural infection process. This study establishes Xtt as one of the few demonstrated hydathode pathogens.

plant biology↗

bioRxiv2024

Annexin and calcium-regulated priming of legume root cells for endosymbiotic infection

Legumes establish endosymbioses with arbuscular mycorrhizal (AM) fungi or rhizobia bacteria to improve mineral nutrition. Symbionts are hosted in privileged habitats, root cortex (for AM fungi) or nodules (for rhizobia) for efficient nutrient exchange. To reach these habitats, plants form cytoplasmic bridges, which are key to predicting and guiding the cellular route of entry of fungal hyphae or rhizobia-filled infection threads (ITs). However, the underlying mechanisms are poorly studied. Here we show that unique ultrastructural changes and Ca2+ spiking signatures, closely linked to MtAnn1 annexin accumulation, accompany rhizobia-associated bridge formation. Loss of MtAnn1 function in M. truncatula affects Ca2+ spike amplitude, cytoplasmic configuration and rhizobia infection efficiency, consistent with a role of MtAnn1 in regulating infection priming. MtAnn1, which evolved in species establishing intracellular symbioses, is also AM-symbiosis-induced and required for proper arbuscule formation. Together, we propose that MtAnn1 is part of an ancient Ca2+-regulatory module for transcellular endosymbiotic infection.

plant biology↗

bioRxiv2023

The penetration of sunflower root tissues by the parasitic plant Orobanche cumana Wallr. is intracellular

O_LIParasitic plants cause yield losses for important crops. Among these, Orobanche cumana Wallr, sunflower broomrape, is one of the major pests for sunflower. Previous studies stated that in most cases, the haustorium, a specific parasitic plant organ, penetrates host roots intercellularly. However, host cellular mechanisms involved during the parasitic cells penetration remained poorly described. C_LIO_LIWe investigated sunflower root cellular behavior during haustorium penetration using various microscopy approaches including live cell imaging of inoculated transgenic fluorescent sunflower roots. C_LIO_LIWe showed that the haustorium of O. cumana penetrated living sunflower root tissues, as a result of the degradation of the host cell wall and the formation of a new host trans-cellular apoplastic compartment for haustorium accommodation. Moreover, broomrape induced cell divisions in outer root tissues at very early stages of the interaction, leading to localized hypertrophy at the site of broomrape attachments. C_LIO_LIThese findings are a change of paradigm in the research field of parasitic plants. They extend host root intracellular accommodation mechanisms initially shown for symbiotic and pathogenic biotrophic fungi to parasitic plants. It paves the way for future understanding and development of resistance to parasitic plants. C_LI Key messageCombination of in vivo confocal, large field and transmission electron microscopy approaches revealed how intimate the relationship between the parasitic plant broomrape (Orobanche cumana Wallr.) and its sunflower host (Helianthus annus L.) is at very early stages of their interaction.

plant biology↗

bioRxiv2020

Rhizobium leguminosarum symbiovar viciae strains are natural wheat endophytes and can stimulate root development and colonization by arbuscular mycorrhizal fungi

O_LIAlthough rhizobia establishing a nitrogen-fixing symbiosis with legumes are also known to promote growth in non-legumes, studies on rhizobia association with wheat roots are scarce. C_LIO_LIWe searched for Rhizobium leguminosarum symbiovar viciae (Rlv) strains naturally competent for wheat roots colonization. We isolated 20 strains and tested the ability of a subset for wheat roots colonization when co-inoculated with other Rlv. We also measured the effect of these strains on wheat root architecture and Arbuscular Mycorrhizal Fungal (AMF) colonization. C_LIO_LIWe found a low diversity of Rlv in wheat roots compared to that observed in the Rlv species complex. Only a few strains, including those isolated from wheat roots, and one strain isolated from pea nodules, were efficient to colonize wheat roots in co-inoculation conditions. These strains had a high ability for endophytic colonization of wheat root and were able to stimulate root development and AMF colonization in single strain inoculation conditions. C_LIO_LIThese results suggest that wheat is an alternative host for some Rlv; nevertheless, there is a strong competition between Rlv strains for wheat root colonization. Furthermore, our study suggests that the level of endophytic colonization is critical for Rlv ability to promote wheat growth. C_LI

microbiology↗

bioRxiv2020

Anatomy of epithemal hydathodes in four monocotyledon plants of economic and academic relevance

Hydathode is a plant organ responsible for guttation in vascular plants, i.e. the release of droplets at leaf margin or surface. Because this organ connects the plant vasculature to the external environment, it is also a known entry site for some vascular pathogens. In this study, we present a detailed microscopic examination of monocot hydathodes for three crops (maize, rice and sugarcane) and the model plant Brachypodium distachyon. Our study highlights both similarities and specificities of those epithemal hydathodes. These observations will serve as a foundation for future studies on the physiology and the immunity of hydathodes in monocots.

plant biology↗