The dynamics of faba bean (Vicia faba L.) parasitism by Orobanche foetida

The dynamics of Orobanche foetida parasitizing faba bean are examined using Petri dish experiments. Rates of broomrape seed germination and seedling attachment to the host roots were quantified on three resistant genotypes (the Egyptian line Giza 429, the Spanish cultivar Baraca, and the Tunisian cultivar Najeh [XBJ90.03-16-1-1-1]) and the susceptible cv. Bachaar. The percentage of O. foetida seed germination (11 to 38%) was lower near the roots of resistant host plants than it was near the roots of ‘Bachaar’ (67%). O. foetida parasitism was followed using three parametric logistic functions. In this way some major parameters of the infection process were quantified: the maximal number (Nmax) and the maximal rate (Rmax) of broomrape attachments to the host roots, the median time required for attachment (T50), the maximal percentage of established tubercles reaching the final growth stage at 70 days after inoculation (DAI) (%max), and the maximal rate of established tubercle growth (R’max). Broomrape attachment was lower and slower in resistant plants, as indicated by low Nmax and Rmax values combined with high T50 values. Furthermore the precocity of the resistant genotypes was correlated with low attachment. The parameters %max and R’max did not discriminate the susceptible cultivar Bachaar from Giza 429 or Baraca. On the other hand, the %max and the R’max were lower in the ‘Najeh’ plants. The findings indicated that both low attachment and limited growth of established tubercles contributed to resistance in the Najeh cultivar

Wild Helianthus species: A reservoir of resistance genes for sustainable pyramidal resistance to broomrape in sunflower

Orobanche cumana Wall., sunflower broomrape, is one of the major pests for the sunflower crop. Breeding for resistant varieties in sunflower has been the most efficient method to control this parasitic weed. However, more virulent broomrape populations continuously emerge by overcoming genetic resistance. It is thus essential to identify new broomrape resistances acting at various stages of the interaction and combine them to improve resistance durability. In this study, 71 wild sunflowers and wild relatives accessions from 16 Helianthus species were screened in pots for their resistance to broomrape at the late emergence stage. From this initial screen, 18 accessions from 9 species showing resistance, were phenotyped at early stages of the interaction: the induction of broomrape seed germination by sunflower root exudates, the attachment to the host root and the development of tubercles in rhizotron assays. We showed that wild Helianthus accessions are an important source of resistance to the most virulent broomrape races, affecting various stages of the interaction: the inability to induce broomrape seed germination, the development of incompatible attachments or necrotic tubercles, and the arrest of emerged structure growth. Cytological studies of incompatible attachments showed that several cellular mechanisms were shared among resistant Helianthus species.This study was performed in the frame of a 3-year project (ResODiv), funded by “Promosol” (the association of French Sunflower and Rapeseed Breeders for promoting these crops).Peer reviewe

Purification et caractérisation du pigment bleu-vert "marennine" synthétisé par la diatomée marine Haslea ostrearia (Gaillon/Bory) Simonsen (propriétés physico-chimiques et activités biologiques)

Haslea ostrearia est une diatomée marine qui synthétise un pigment bleu-vert appelé "marennine". Il existe une localisation intracellulaire (IMn) et extracellulaire (EMn) du pigment. Cette diatomée est responsable de la coloration verte des branchies d'huîtres de culture.Une méthode de purification et de quantification de l'IMn et de l'EMn est mise au point. Elle fait appel à l'ultrafiltration sur membranes et à la CLHP (exclusion-diffusion et échange d'anions), couplée à un détecteur UV-visible à barrette de diodes. La caractérisation des molécules purifiées révèle la nature polyphénolique de la marennine. L'étude comparée des paramètres physico-chimiques, masses moléculaires et propriétés spectrales notamment, montre que l'IMn et l'EMn possèdent des structures moléculaires distinctes. Par alleurs, l'IMn et l'EMn présentent des activités cytostatiques in vitro à l'encontre de cellules cancéreuses, de bactéries et de microalgues, ainsi que des propriétés anti-UV et antioxydantes.Haslea ostrearia is a marine diatom that synthesizes a blue-green pigment called "marennine". This pigment is found under an intra- (IMn) and an extracellular form (EMn). The diatom is responsible for the blue colour of the cultured oyster gills. A method for the purification and the quantification of IMn and EMn is perfected. It uses an ultrafiltration process through membranes and a gel-filtration / anion-exchange HPLC interfaced with a photodiode-array detector. The characterisation of the purified molecules reveals the polyphenolic nature of marennine. The comparative analysis of physico-chemical parameters, molecular weights and spectral properties among others, shows that IMn and EMn have distinct molecular structures. Moreover, IMn and EMn display in vitro cytostatic activities against cancerous cell lines, bacteria and microalgae, as well as anti-UV and antioxidative properties.NANTES-BU Sciences (441092104) / SudocSudocFranceF

Efficacité du contrôle de l'ovulation par traitement gonadotrope dans une population hétérogène de brochet (Esox lucius) : relation avec le stade ovocytaire et comparaison avec les résultats d'ovulations spontanées

Efficacité du contrôle de l'ovulation par traitement gonadotrope dans une population hétérogène de brochet (Esox lucius) : relation avec le stade ovocytaire et comparaison avec les résultats d'ovulations spontanée

CYP707As are effectors of karrikin and strigolactone signalling pathways in Arabidopsis thaliana and parasitic plants

Karrikins stimulate Arabidopsis thaliana germination, while parasitic weeds of the Orobanchaceae family have evolved to respond to host‐exuded compounds such as strigolactones, dehydrocostus lactone, and 2‐phenylethyl isothiocyanate. In Phelipanche ramosa, strigolactone‐induced germination was shown to require one of the CYP707A proteins involved in abscisic acid catabolism. Here, germination and gene expression were analyzed to investigate the role of CYP707As in germination of both parasitic plants and Arabidopsis upon perception of germination stimulants, after using pharmacological inhibitors and Arabidopsis mutants disrupting germination signals. CYP707A genes were up‐regulated upon treatment with effective germination stimulants in both parasitic plants and Arabidopsis. Obligate parasitic plants exhibited both an intensified up‐regulation of CYP707A genes and increased sensitivity to the CYP707A inhibitor Abscinazole‐E2B, while Arabidopsis cyp707a mutants still positively responded to germination stimulation. In Arabidopsis, CYP707A regulation required the canonical karrikin signaling pathway KAI2/MAX2/SMAX1 and the transcription factor WRKY33. Finally, CYP707As and WRKY33 also modulated Arabidopsis root architecture in response to the synthetic strigolactone rac‐GR24, and wrky33‐1 exhibited a shoot hyper‐branched phenotype. This study suggests that the lack of host‐independent germination in obligate parasites is associated with an exacerbated CYP707A induction, and that CYP707As and WRKY33 are new players involved in a variety of strigolactone/karrikin responses

Colorimetric study of marennine, a blue-green pigment from the diatom Haslea ostrearia responsible for natural greening of cultured oyster.

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Strigolactones (SLs) modulate the plastochron by regulating KLUH (KLU) transcript abundance in Arabidopsis

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