Biology subjects

Frendo, P.

Publications and source records attributed to Frendo, P..

4 recordsLinked to original sources

bioRxiv2025

Plant and Aphid Genotypes Modulate Legume Rhizobium-Induced Defense Against Aphids

Sustainable protein production is needed to ensure food security while mitigating climate change. Leguminous crops contribute to these goals by providing protein-rich seeds and improving soil fertility through nitrogen-fixing symbiosis (NFS) with rhizobia. Beyond their nutritional and agronomic benefits, legumes face major challenges from insect herbivores such as the pea aphid, Acyrthosiphon pisum. While NFS can enhance plant defences against aphids, the influence of plant and aphid genotypic variation on these rhizobia-mediated effects remains poorly understood. Here, we investigated how genotype interactions influence rhizobia-mediated defence priming by using two Medicago truncatula genotypes (A17 and R108) grown under NFS with Sinorhizobium meliloti 2011 or nitrate (NI) feeding conditions and infested with three clonal lines representing two pea aphid biotypes. We analysed aphid performance, plant fitness, and plant leaf expression of defence genes associated with the jasmonic acid (JA) and salicylic acid (SA) signalling pathways over a 12-day period following aphid infestation. Aphid fitness varied significantly with both plant and aphid genotypes and was further modulated by rhizobia inoculation. Expression of defence marker genes involved in SA and JA pathway was dependent on specific plant-aphid genotype combinations and was significantly modulated by rhizobia inoculation. This pattern suggests that both SA- and JA-mediated plant defences contribute to regulating aphid weight, possibly through different mechanisms or in response to different plant-aphid interactions. Our study shows that plant and aphid genotypes, rhizobia inoculation and interactions (G x G x R) are thus central components driving plantaphid-rhizobia interaction dynamics. Our study highlights importance of genetic context and microbial symbiosis in structuring multitrophic interactions and suggests new opportunities to optimize pest resistance using plant-beneficial microbial associations.

plant biology↗

bioRxiv2024

Identification of regulatory promoter sequences directing MtCP6 transcription at the onset of nodule senescence in Medicago truncatula.

O_LIThe symbiotic association of legumes with rhizobia results in the formation of new root organs called nodules. However, the lifespan of nodules is limited by the senescence process. Increased proteolytic activity is one of the hallmarks of nodule senescence. In Medicago truncatula, a papain cysteine protease encoding gene, MtCP6, is a marker for the onset of nodule senescence under both developmental and stress-induced pathways. C_LIO_LITo identify promoter regions conferring MtCP6 senescence-related expression, progressive MtCP6 promoter deletions were generated and the resulting sequences were fused with a reporter gene for promoter::GUS fusion analysis in transgenic M. truncatula roots. C_LIO_LIIn planta, a minimal promoter sequence of 67 bp was identified as sufficient for specific spatiotemporal transcriptional activation of MtCP6 in nodules. The functionality of this cis-regulatory sequence, thereafter named Nodule Senescence (NS), was validated by both gain- and loss-of-function approaches. C_LIO_LIERF091, an AP2/ERF family transcription factor, was identified in a yeast one-hybrid (Y1H) screen as an NS-box interacting factor, and shown to mediate transcription activation of a NS-box:GUS reporter in transactivation assays in Nicotiana benthamiana. C_LIO_LIThis work uncovered a new senescence-related nodule specific cis-regulatory region (NS-box) and provided evidence for the likely involvement of a stress-related ERF family member in the regulation of MtCP6, at the onset of nodule senescence. C_LI

plant biology↗

bioRxiv2024

Differential induction of Medicago truncatula defence metabolites in response to rhizobial symbiosis and pea aphid infestation

O_LILegumes symbiosis with rhizobial nitrogen-fixing bacteria enable them to grow in nitrate-depleted soils. Rhizobial symbioses also induces systemic plant defence against bioagressors. C_LIO_LIWe investigate how nitrogen-fixing symbiosis (NFS) in the legume Medicago truncatula can prime plant defence against the pea aphid Acyrthosiphon pisum. We analysed metabolite modification both by LC-MS and GC-MS and defence pathway gene expression by qPCR in leaves of both NFS and nitrate-fed (non-inoculated; NI) plants after aphid infestation (Amp). C_LIO_LIThe accumulation of primary and secondary metabolites was modulated by both NFS and aphid infestation. 62 defense-related metabolites such as salicylate, pipecolate, gentisic acid and several soluble sugars were differentially regulated by aphid infestation in both NFS and NI conditions. 19 metabolites, including triterpenoid saponins, accumulated specifically in NFS_Amp conditions. Gene expression analysis showed that aphid-infested plants exhibited significantly higher expression of Chalcone isomerase, flavonol synthase, hydroxyisoflavone-O-methyl transferase and Pterocarpan synthase, while D-pinitol dehydrogenase was only significantly induced in NI infested leaves. C_LIO_LIOur data suggest that NFS, in addition to being a plant nitrogen provider, stimulates specific legume defenses upon pest attack and should also be considered as a potential tool in Integrated Pest Management strategy. C_LI

plant biology↗

bioRxiv2023

SydR, a redox-sensing MarR-type regulator of Sinorhizobium meliloti, is crucial for symbiotic infection of Medicago truncatula roots

Rhizobia associate with legumes and induce the formation of nitrogen-fixing nodules. The regulation of bacterial redox state plays a major role in symbiosis and Reactive Oxygen Species (ROS) produced by the plant are known to activate signaling pathways. However, only a few redox-sensing transcriptional regulators (TRs) have been characterized in the microsymbiont. Here, we describe SydR, a novel redox-sensing TR of S. meliloti that is essential for the establishment of symbiosis with Medicago truncatula. SydR, a MarR-type TR, represses the expression of the adjacent gene SMa2023 in growing cultures, and this repression is alleviated by NaOCl, tert-butyl, or H2O2 treatment. Gels shift assays strongly suggest that SydR binds to TATCGCGATA motif in the sydR-SMa2023 intergenic region in a redox-dependent manner. Furthermore, site-directed mutagenesis demonstrated that the oxidative inhibition of SydR involves the formation of an intermolecular C16-C16 disulfide bond. The inactivation of sydR did not alter the sensitivity of S. meliloti to NaOCl, tert-butyl, or H2O2, nor did it affect the response to oxidants of the roGFP2-Orp1 redox biosensor expressed within bacteria. However, in planta, {Delta}sydR mutation impaired the formation of root nodules. Microscopic observations and analyses of marker gene expression showed that the {Delta}sydR mutant is arrested at an early stage of the bacterial infection process. Altogether, these results demonstrated that SydR is a redox sensing MarR-type TR that plays a key role in the regulation of symbiosis with M. truncatula. IMPORTANCEThe nitrogen-fixing symbiosis between rhizobia and legumes has an important ecological role in the nitrogen cycle, contributes to nitrogen enrichment of soils, and can improve plant growth in agriculture. This interaction is initiated in the rhizosphere by a molecular dialog between the two partners, resulting in plant root infection and formation of root nodules, where bacteria reduce the atmospheric nitrogen into ammonium. This symbiosis involves modifications of the bacterial redox state in response to reactive oxygen species produced by the plant partner. Here, we show that SydR, a transcriptional regulator of the Medicago symbiont Sinorhizobium meliloti, acts as a redox-responsive repressor that is crucial for the development of root nodules and contributes to the regulation of bacterial infection in S. meliloti / Medicago truncatula symbiotic interaction.

microbiology↗