Biology subjects

Brun, G.

Publications and source records attributed to Brun, G..

4 recordsLinked to original sources

bioRxiv2023

Acclimation kinetics of the holoparasitic weed Phelipanche ramosa (Orobanchaceae) during excessive light and heat conditions

Holoparasitic plants, such as broomrape, have abandoned a photosynthesis, relying entirely on the resources of host plants. This departure from an autotrophic lifestyle necessitates significant genetic and metabolic adaptations, offering a unique model system to elucidate responses independent of canonical plastid functions in green plants. In this study, we examined the acclimation kinetics of the holoparasitic weed Phelipanche ramosa (broomrape) under unfavorable temperature and excessive light conditions through a comprehensive time-course analysis of RNA sequence data and physiological monitoring. Our work unveils that suboptimal abiotic conditions induce transcriptional changes in the parasitic plant, involving coordinated expression of nuclear and plastid-encoded genes. Notably, magnesium transporters, critical for heat-induced chlorophyll conversion, were enriched among heat-repressed genes. Additionally, multiple copies of chloroplast-targeted DnaJ proteins, responsible for maintaining CO2 assimilation capacity in non-parasitic plants, were identified. Comparative expression analysis with the parasites host plants, tomato and Arabidopsis, revealed distinct patterns for certain plastid genes in Phelipanche. Furthermore, an elevation in reactive oxygen species (ROS) in the parasite coincided with the upregulation of numerous heat shock protein (HSP) genes, including HSP21, which associates with thylakoid membranes in photosynthetic plants; noteworthily, thylakoids are absent from Phelipanches plastids. Collectively, our findings suggest that plastids of the nonphotosynthetic model plant retains their ancestral role as environmental sensors. This research opens new avenues for functional-genetic research into the nuanced roles of plastids in the lifecycles of parasitic plants.

plant biology↗

bioRxiv2023

Comparative gene expression analysis of differentiated terminal and lateral haustoria of the obligate root parasitic plant Phelipanche ramosa (Orobanchaceae)

AO_SCPLOWBSTRACTC_SCPLOWBranched broomrape (Phelipanche ramosa, Orobanchaceae) is the most important parasitic weed of oilseed and vegetable crops in Europe. Deciphering the parasites basic biology and genetics underpinning adaptations to parasitism are essential for effective weed management. Here, we compared the gene expression profiles of differentiated terminal haustoria, formed immediately after the germination of P. ramosa with those of the parasites adventitious roots and lateral haustoria, which develop on the latter as it grows. Principal component analysis and functional annotation of differentially expressed genes indicate a greater transcriptional similarity between adventitious roots and lateral haustoria compared to terminal haustoria. Genes involved in hydrogen peroxide catabolic processes and mucilage metabolic processes were more abundant in lateral haustoria compared to adventitious roots, indicating that secondary host attachment involves secretion of adhesive compounds, cell wall modification, and a termination of the developmental program associated with root growth. In terminal haustoria, phytohormonal signaling pathways for post-germination growth and meristem development were the most prominent expression profile difference to lateral haustoria. Besides this, wide similarity of expressed genes between lateral and terminal haustoria suggest overlapping pathways underlying haustorium differentiation and a conserved functional relevance of both haustoria types at maturity. Together, our study provides first insights into the transcriptional landscapes of the primary organs securing P.ramosas nutritional success. However, more research is needed to investigate whether the parasites various haustorium types differ in their sensitivities to environmental stimuli and whether transcriptional divergence in terminal and lateral haustoria of P. ramosa reflect differences regarding their developmental origin.

plant biology↗

bioRxiv2023

Aging seeds of weedy broomrapes and witchweeds lose sensitivity to strigolactones as DNA demethylates

Broomrapes (Phelipanche and Orobanche spp.) and witchweeds (Striga and Alectra spp.) are obligate root parasitic weeds responsible for major crop yield losses worldwide. Their success in agricultural landscapes is attributable to their ability to produce thousands of long-lived minute seeds that coordinate their germination with the presence of nearby hosts by perceiving host-derived strigolactones. Nevertheless, the processes underlying the alleged decade(s)-long persistence in the field are understudied. Using an accelerated seed aging method coupled to germination and ELISA bioassays, we report that the loss of seed viability and germinability along seed aging is accompanied by a decrease in both strigolactone sensitivity and global DNA methylation. Our results also suggest that seeds of broomrapes are longer-lived than those of witchweeds. Overall, this study deems to initiate further research into how epigenetic mechanisms contribute to alterations in seed viability in parasitic weeds, and how seed aging influence seed responses to their environment.

plant biology↗

bioRxiv2020

A Phelipanche ramosa KAI2 Protein Perceives enzymatically Strigolactones and Isothiocyanates

Phelipanche ramosa is an obligate root-parasitic weed threatening major crops in central Europe. For its germination, it has to perceive various structurally diverging host-exuded signals, including isothiocyanates (ITCs) and strigolactones (SLs). However, the receptors involved are still uncharacterized. Here, we identified five putative SL receptors in P. ramosa, of which PrKAI2d3 is involved in seed germination stimulation. We established the high plasticity of PrKAI2d3, allowing interaction with different chemicals, including ITCs. The SL perception mechanism of PrKAI2d3 is similar to that of endogenous SLs in non-parasitic plants. We provide evidence that the PrKAI2d3 enzymatic activity confers hypersensitivity to SLs. Additionally, we demonstrated that methylbutenolide-OH binds PrKAI2d3 and stimulates P. ramosa germination with a bioactivity comparable to that of ITCs. This study highlights that P. ramosa has extended its signal perception system during evolution, a fact to be considered in the development of specific and efficient biocontrol methods.

plant biology↗