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Ralstonia solanacearum virulence in tomato seedlings inoculated by leaf clipping
No full textRalstonia solanacearum is a phytopathogenic bacterium that colonizes the xylem vessels of host plants leading to a lethal wilt disease. Although several studies have investigated the virulence of R. solanacearum on adult host plants, infection studies of this pathogen on the seedling stages of hosts are less common. In a preliminary observation, inoculation of R. solanacearum F1C1 on 6- to 7-day-old tomato seedlings by a simple leaf-clip strategy resulted in a lethal pathogenic condition in seedlings that eventually killed these seedlings within a week post-inoculation. This prompted testing of the effect of this inoculation technique in seedlings from different cultivars of tomato and similar results were obtained. Colonization and spread of the bacteria throughout the infected seedlings was demonstrated using gus-tagged R. solanacearum F1C1. The same method of inoculating tomato seedlings was used with R. solanacearum GMI1000 and independent mutants of R. solanacearum GMI1000, deficient in the virulence genes hrpB, hrpG, phcA and gspD. Wildtype R. solanacearum GMI1000 was found to be virulent on tomato seedlings, whereas the mutants were found to be non-virulent. This leaf-clip technique, for inoculation of tomato seedlings, has the potential to be a valuable approach, saving time, space, labour and costs
Genome-wide association studies with proteomics data reveal genes important for synthesis, transport and packaging of globulins in legume seeds
No full textAGAP : équipe GE2popImproving nutritional seed quality is an important challenge in grain legume breeding. However, the genes controlling the differential accumulation of globulins, which are major contributors to seed nutritional value in legumes, remain largely unknown. We combined a search for protein quantity loci with genome-wide association studies on the abundance of 7S and 11S globulins in seeds of the model legume species Medicago truncatula. Identified genomic regions and genes carrying polymorphisms linked to globulin variations were then cross-compared with pea (Pisum sativum), leading to the identification of candidate genes for the regulation of globulin abundance in this crop. Key candidates identified include genes involved in transcription, chromatin remodeling, post-translational modifications, transport and targeting of proteins to storage vacuoles. Inference of a gene coexpression network of 12 candidate transcription factors and globulin genes revealed the transcription factor ABA-insensitive 5 (ABI5) as a highly connected hub. Characterization of loss-of-function abi5 mutants in pea uncovered a role for ABI5 in controlling the relative abundance of vicilin, a sulfur-poor 7S globulin, in pea seeds. This demonstrates the feasibility of using genome-wide association studies in M. truncatula to reveal genes that can be modulated to improve seed nutritional value
Phylogeny and evolution of shallow-water squat lobsters (Decapoda, Galatheoidea) from the Indo-Pacific
No full textSquat lobsters have a worldwide distribution and are highly visible crustaceans living in a broad range of habitats. In this study, partial sequences of two mitochondrial DNA genes (16S rRNA and COI) and a nuclear gene (H3) were obtained for all but one of the known species of the shallow-water genera Sadayoshia (Munididae) and Lauriea, Macrothea and Triodonthea (Galatheidae). Lauriea siagiani appeared to be phylogenetically closer to Triodonthea and Macrothea than to other Lauriea species, suggesting the need for taxonomic re-evaluation of these taxa. All species of Sadayoshia formed a monophyletic group that would have diverged during the Paleogene (around 50Mya). Our results support the hypothesis that the late Paleogene-Neogene transition was a period of rapid diversification for shallow-water species of both Galatheidae and Munididae in the Indo-Pacific region. This is probably related to high tectonic activity among the Eurasian, Philippine Sea, Indo-Australian and Pacific plates and corresponding changes in distribution of habitats and ocean currents during the late Paleogene. Finally, the tropical south-west Pacific province is identified as a major diversification centre for shallow-water squat lobsters, from where species dispersed to other Pacific and Indian Ocean regions
Diversity spurs diversification in ecological communities
No full textDiversity is a fundamental, yet threatened, property of ecological systems. The idea that diversity can itself favour diversification, in an autocatalytic process, is very appealing but remains controversial. Here, we study a generalized model of ecological communities and investigate how the level of initial diversity influences the possibility of evolutionary diversification. We show that even simple models of intra- and inter-specific ecological interactions can predict a positive effect of diversity on diversification: adaptive radiations may require a threshold number of species before kicking-off. We call this phenomenon DDAR (diversity-dependent adaptive radiations) and identify mathematically two distinct pathways connecting diversity to diversification, involving character displacement and the positive diversity-productivity relationship. Our results may explain observed delays in adaptive radiations at the macroscale and diversification patterns reported in experimental microbial communities, and shed new light on the dynamics of ecological diversity, the diversity-dependence of diversification rates, and the consequences of biodiversity loss
Geographic Variation of Diapause Induction Rates in Trichogramma drendrolimi (Hymenoptera: Trichogrammatidae) in China
No full textDiapause variation is a key factor affecting the development and success of parasitoids employed as biological control agents. Trichogramma dendrolimi Matsumura is mass-reared for biocontrol purposes in several countries around the world. Here we investigated the rate of diapause induction in three populations of T. dendrolimi from different regions in China: Heilongjiang (44 degrees 55' N, 128 degrees 26' E; HLJ), Liaoning (40 degrees 18' N, 123 degrees 22' E; LN), and Jiangsu province (32 degrees 30' N, 120 degrees 09' E; JS). We measured the rates of diapause induction for populations from each region when exposed to temperatures of 8, 10, 12, and 14 degrees C, for periods ranging from 5 to 35 d. Results showed that both the temperature and exposure duration influenced diapause induction in the three populations of T. dendrolimi. The HLJ and LN populations showed the highest percentage of diapause under 12 and 10 degrees C, regardless of time period tested. After 20 d at 12 and 10 degrees C, 97.42% and 95.94% of individuals of HLJ and LN, respectively, entered diapause. After treatment for 20-35 d under 8 degrees C, or 15-25 d under 10 degrees C, the diapause rate of LN was higher than those of the other two populations. In contrast, the higher temperatures (1214 degrees C) induced diapause rapidly and steadily in HLJ. The diapause rate of JS was low for all temperatures and time periods. After 30 d at 12 degrees C, the JS population reached its highest diapause rate (29.56%). Our results showed significant variance in diapause rates among geographically distinct populations of T. dendrolimi in response to various abiotic conditions
Protocol For: Extraction of high-molecular-weight genomic DNA for long-read sequencing of single molecules
No full textProtocoleProtocol For: Extraction of high-molecular-weight genomic DNA for long-read sequencing of single molecule
The sunflower genome provides insights into oil metabolism, flowering and Asterid evolution
No full textThe domesticated sunflower, Helianthus annuus L., is a global oil crop that has promise for climate change adaptation, because it can maintain stable yields across a wide variety of environmental conditions, including drought. Even greater resilience is achievable through the mining of resistance alleles from compatible wild sunflower relatives, including numerous extremophile species. Here we report a high-quality reference for the sunflower genome (3.6 gigabases), together with extensive transcriptomic data from vegetative and floral organs. The genome mostly consists of highly similar, related sequences and required single-molecule real-time sequencing technologies for successful assembly. Genome analyses enabled the reconstruction of the evolutionary history of the Asterids, further establishing the existence of a whole-genome triplication at the base of the Asterids II clade and a sunflower-specific whole-genome duplication around 29 million years ago. An integrative approach combining quantitative genetics, expression and diversity data permitted development of comprehensive gene networks for two major breeding traits, flowering time and oil metabolism, and revealed new candidate genes in these networks. We found that the genomic architecture of flowering time has been shaped by the most recent whole-genome duplication, which suggests that ancient paralogues can remain in the same regulatory networks for dozens of millions of years. This genome represents a cornerstone for future research programs aiming to exploit genetic diversity to improve biotic and abiotic stress resistance and oil production, while also considering agricultural constraints and human nutritional needs
Solubility equilibrium and surface reactivity at solid/liquid interfaces of relevance to disposal of nuclear waste
No full textInternational audienc
L2 pragmatic input in EFL classrooms in France: An acquisitional issue
No full textInternational audienc
