A conserved lysine residue of plant Whirly proteins is necessary for higher order protein assembly and protection against DNA damage

All organisms have evolved specialized DNA repair mechanisms in order to protect their genome against detrimental lesions such as DNA double-strand breaks. In plant organelles, these damages are repaired either through recombination or through a microhomology-mediated break-induced replication pathway. Whirly proteins are modulators of this second pathway in both chloroplasts and mitochondria. In this precise pathway, tetrameric Whirly proteins are believed to bind single-stranded DNA and prevent spurious annealing of resected DNA molecules with other regions in the genome. In this study, we add a new layer of complexity to this model by showing through atomic force microscopy that tetramers of the potato Whirly protein WHY2 further assemble into hexamers of tetramers, or 24-mers, upon binding long DNA molecules. This process depends on tetramer–tetramer interactions mediated by K67, a highly conserved residue among plant Whirly proteins. Mutation of this residue abolishes the formation of 24-mers without affecting the protein structure or the binding to short DNA molecules. Importantly, we show that an Arabidopsis Whirly protein mutated for this lysine is unable to rescue the sensitivity of a Whirly-less mutant plant to a DNA double-strand break inducing agent

Structure and organization of the leghemoglobin genes in soybean

The organization and structure of the leghemoglobin (Lb) genes in soybean have been investigated. Using molecular cloning techniques, a Lb-cDNA recombinant molecule, pLb1, was prepared and characterized. Hybridization of this clone of genomic DNA revealed the presence of at least seven Lb genes in the soybean genome. The arrangement of these genes appeared to be the same in DNA isolated from infected or uninfected tissues. The plasmid pLb1 was also used to isolate three Lb sequences from a genomic library constructed in (lamda) Charon4 vector. Nucleotide sequence analysis showed that one Lb gene, present on an 11.5 kilobases (kb) Eco RI genomic fragment, spans about 1 200 nucleotides and appears to code for Lbc(,3). Its coding sequence is interrupted at amino acid positions 32 to 33, 68 to 69 and 103 to 104. The intervening sequences, as well as the 5' and 3' flanking regions of this gene, contain some consensus sequences found in other eukaryotic genes. The length of the 5'-untranslated region is 49 bases as determined by nuclease S1 mapping. R-loop analysis of the recombinant phage containing the 11.5 kb Eco RI fragment showed that another Lb gene is located 2.5 kb away. The nucleotide sequences of the second gene showed that this gene is incomplete, containing only two exons. The deduced amino acid sequence of this gene, although showing 78% homology with the corresponding region of the other Lb gene, is not represented in any of the known Lb proteins. Both genes are oriented in the same direction with respect to the coding strand. Analysis of the sequence present in a second genomic clone containing a 4.2 kb Eco RI fragment revealed a truncated Lb gene showing homology with the last exon and the non-coding region at the 3' end of the two other Lb genes. A very high homology is found among the nucleotide sequence of the Lbc(,3), Lba and Lbc(,1) genes. Comparison of the intervening sequences of these genes indicated that they diverged mainly through the creati

Diagnose écologique du lac Dugas

Suite au constat de la diminution du succès de pêche à l’omble de fontaine (Salvelinus fontinalis) sur le lac Dugas, plan d’eau situé dans du bassin hydrographique de la rivière Rimouski, une diagnose écologique a été réalisée les 6 et 7 septembre 2002. Les objectifs principaux ont consisté en la détermination de la ou des causes potentielles de cette baisse de rendement ainsi que de l’évaluation de l’exploitation et du potentiel salmonicole, dans le but de soumettre des recommandations adéquates pour remédier à la situation. Afin d’évaluer correctement le profil du lac, il a été nécessaire de déterminer la bathymétrie de ce dernier ainsi que la physico-chimie de l’eau, puis d’inventorier les sites potentiels de frai en lac et en ruisseaux. Une pêche expérimentale a permis de procéder à un inventaire de la population de salmonidés et par la suite de déterminer l’état des stocks, en évaluant certaines caractéristiques biométriques. Ainsi un verdict a été rendu suite à l’analyse des résultats obtenus de la pêche expérimentale, couplés à ceux des données de pêche sportive des 23 dernières années, fournies par les gestionnaires de la Réserve. L’omble de fontaine fut la seule espèce capturée lors de la pêche expérimentale dans le lac Dugas. Cette situation favorise le potentiel salmonicole de ce plan d’eau. La bathymétrie et la physico-chimie du lac Dugas confirment que l’habitat est favorable au développement d’une population d’ombles de fontaine. Toute ces affirmations sont confirmées par le résultat de la pêche expérimentale avec un taux de capture par unité d’effort (CPUE) de 58,8 ombles par nuit-filet. Les fortes fluctuations observées au niveau la récolte au cours des vingt-trois dernières années sont le résultat d’un effort de pêche présentant de grandes variations . Par contre, comme le lac offre un bon potentiel salmonicole, la situation peut être facilement corrigée par une meilleure gestion de l’exploitation, basée sur un effort de pêche annuelle de 40 jours-pêche. Des recommandations sont aussi proposées au niveau du tributaire et de l’émissaire

Molecular genetics of plant-microbe interactions : proceedings of the third International Symposium on the molekular genetics of plant-microbe Associations, Montreal, Quebec, Canada, July 27-31, 1986

IndeksBibliografi hlm. Setiap babxxxii, 338 hlm. : il. ; 23 cm

Purification, crystallization and preliminary X-ray diffraction analysis of the Whirly domain of StWhy2 in complex with single-stranded DNA

The Whirly domain of StWhy2 was crystallized both in the free form and in complex with single-stranded DNA

Time- and cost-efficient identification of T-DNA insertion sites through targeted genomic sequencing.

Forward genetic screens enable the unbiased identification of genes involved in biological processes. In Arabidopsis, several mutant collections are publicly available, which greatly facilitates such practice. Most of these collections were generated by agrotransformation of a T-DNA at random sites in the plant genome. However, precise mapping of T-DNA insertion sites in mutants isolated from such screens is a laborious and time-consuming task. Here we report a simple, low-cost and time efficient approach to precisely map T-DNA insertions simultaneously in many different mutants. By combining sequence capture, next-generation sequencing and 2D-PCR pooling, we developed a new method that allowed the rapid localization of T-DNA insertion sites in 55 out of 64 mutant plants isolated in a screen for gyrase inhibition hypersensitivity