Turning Meiosis into Mitosis

The mutation of as few as three genes in a sexual plant transforms meiosis into mitosis and results in diploid gametes that are genetically identical to the mother plant. This phenotype resembles apomeiosis, which is a major step in apomixis

Mutations in AtPS1 (Arabidopsis thaliana Parallel Spindle 1) Lead to the Production of Diploid Pollen Grains

Polyploidy has had a considerable impact on the evolution of many eukaryotes, especially angiosperms. Indeed, most—if not all—angiosperms have experienced at least one round of polyploidy during the course of their evolution, and many important crop plants are current polyploids. The occurrence of 2n gametes (diplogametes) in diploid populations is widely recognised as the major source of polyploid formation. However, limited information is available on the genetic control of diplogamete production. Here, we describe the isolation and characterisation of the first gene, AtPS1 (Arabidopsis thaliana Parallel Spindle 1), implicated in the formation of a high frequency of diplogametes in plants. Atps1 mutants produce diploid male spores, diploid pollen grains, and spontaneous triploid plants in the next generation. Female meiosis is not affected in the mutant. We demonstrated that abnormal spindle orientation at male meiosis II leads to diplogamete formation. Most of the parent's heterozygosity is therefore conserved in the Atps1 diploid gametes, which is a key issue for plant breeding. The AtPS1 protein is conserved throughout the plant kingdom and carries domains suggestive of a regulatory function. The isolation of a gene involved in diplogamete production opens the way for new strategies in plant breeding programmes and progress in evolutionary studies

The Genome Sequence of the Grape Phylloxera Provides Insights into the Evolution, Adaptation, and Invasion Routes of an Iconic Pest

Background: Although native to North America, the invasion of the aphid-like grape phylloxera Daktulosphaira vitifoliae across the globe altered the course of grape cultivation. For the past 150 years, viticulture relied on grafting-resistant North American Vitis species as rootstocks, thereby limiting genetic stocks tolerant to other stressors such as pathogens and climate change. Limited understanding of the insect genetics resulted in successive outbreaks across the globe when rootstocks failed. Here we report the 294-Mb genome of D. vitifoliae as a basic tool to understand host plant manipulation, nutritional endosymbiosis, and enhance global viticulture. Results: Using a combination of genome, RNA, and population resequencing, we found grape phylloxera showed high duplication rates since its common ancestor with aphids, but similarity in most metabolic genes, despite lacking obligate nutritional symbioses and feeding from parenchyma. Similarly, no enrichment occurred in development genes in relation to viviparity. However, phylloxera evolved > 2700 unique genes that resemble putative effectors and are active during feeding. Population sequencing revealed the global invasion began from the upper Mississippi River in North America, spread to Europe and from there to the rest of the world. Conclusions: The grape phylloxera genome reveals genetic architecture relative to the evolution of nutritional endosymbiosis, viviparity, and herbivory. The extraordinary expansion in effector genes also suggests novel adaptations to plant feeding and how insects induce complex plant phenotypes, for instance galls. Finally, our understanding of the origin of this invasive species and its genome provide genetics resources to alleviate rootstock bottlenecks restricting the advancement of viticulture

Progresses of the international community to understand sunflower–pollinator interactions through multiscale approaches

The first web conference on sunflower–pollinator interactions gathered the international community around a major topic for sunflower productivity and ecosystemic biodiversity. Insect-mediated pollination is important for increasing sunflower seed yield, but is dependent on environmental factors. Climate change can impact sunflower-pollinator interactions by influencing both plant and pollinator behavior. Natural or artificially elevated ambient temperatures appear to accelerate floret development and advance the timing of pollen presentation to coincide with pollinator activities. Drought showed no major effect on morphological traits such anther or corolla length, but dramatically reduced nectar and pollen productions. Flavonol-glycoside conjugates lower head transpiration thereby mitigating deleterious effects of abiotic stresses. Wild pollinators show fine scale preferences among sunflower varieties, likely due to the different resource focus of wild and managed honeybees. Agricultural practices such as planting flower strips to provide nesting sites for wild pollinators, or supplementing crop plots with hives, can have a positive effect on insect-mediated pollination efficiency and ensure optimal yields. All together, recent results on sunflower–pollinator interactions pave the way to develop varieties and corresponding cropping systems more favorable to pollinator biodiversity while maintaining high yields in the context of climate change

Progres le communaute internationale pour la comprehension des interactions tournesol pollinisateurs par une approche multi-echelle

The first web conference on sunflower–pollinator interactions gathered the international community around a major topic for sunflower productivity and ecosystemic biodiversity. Insect-mediated pollination is important for increasing sunflower seed yield, but is dependent on environmental factors. Climate change can impact sunflower-pollinator interactions by influencing both plant and pollinator behavior. Natural or artificially elevated ambient temperatures appear to accelerate floret development and advance the timing of pollen presentation to coincide with pollinator activities. Drought showed no major effect on morphological traits such anther or corolla length, but dramatically reduced nectar and pollen productions. Flavonol-glycoside conjugates lower head transpiration thereby mitigating deleterious effects of abiotic stresses.Wild pollinators show fine scale preferences among sunflower varieties, likely due to the different resource focus of wild and managed honeybees. Agricultural practices such as planting flower strips to provide nesting sites for wild pollinators, or supplementing crop plots with hives, can have a positive effect on insect-mediated pollination efficiency and ensure optimal yields. All together, recent results on sunflower–pollinator interactions pave the way to develop varieties and corresponding cropping systems more favorable to pollinator biodiversity while maintaining high yields in the context of climate change.La première conférence en ligne sur les interactions entre les tournesols et les pollinisateurs a réuni la communauté internationale autour d’un sujet majeur pour la productivité des tournesols et la biodiversité écosystémique. La pollinisation par les insectes est importante pour augmenter le rendement en graines de tournesol, mais elle dépend de facteurs environnementaux. Le changement climatique peut avoir un impact sur les interactions entre les tournesols et les pollinisateurs en influençant le comportement des plantes et des pollinisateurs. Les températures élevées (canicule ou de façon artificielle) accélèrent le développement des fleurons et avancent la présentation du pollen devant coïncider avec l’activité des pollinisateurs. La sécheresse n’a montré aucun effet majeur sur les traits morphologiques tels que la longueur des anthères ou des corolles, mais a considérablement réduit la production de nectar et de pollen. Les conjugués de flavonol-glycosides réduisent la transpiration des capitules, pouvant ainsi atténuer les effets néfastes des stress abiotiques. Les pollinisateurs sauvages montrent des préférences à petite échelle parmi les variétés de tournesols, probablement en raison des différentes ressources auxquelles les abeilles sauvages et domestiques ont accès. Les pratiques agricoles telles que la plantation de bandes fleuries pour fournir des sites de nidification aux pollinisateurs sauvages, ou l’apport de ruches près des parcelles de culture, peuvent avoir un effet positif sur l’efficacité de la pollinisation par les insectes et garantir des rendements optimaux. Dans l’ensemble, les résultats récents sur les interactions entre les tournesols et les pollinisateurs ouvrent la voie au développement de variétés et de systèmes de culture plus favorables à la biodiversité des pollinisateurs tout en maintenant des rendements élevés dans le contexte du changement climatique.http://www.ocl-journal.orgam2024Forestry and Agricultural Biotechnology Institute (FABI)Plant Production and Soil ScienceSDG-02:Zero HungerSDG-13:Climate actionSDG-15:Life on lan

The Nanovirus-Encoded Clink Protein Affects Plant Cell Cycle Regulation through Interaction with the Retinoblastoma-Related Protein

Nanoviruses, multicomponent single-stranded DNA plant viruses, encode a unique cell cycle link protein, Clink, that interacts with retinoblastoma-related proteins (RBR). We have established transgenic Arabidopsis thaliana lines that conditionally express Clink or a Clink variant deficient in RBR binding. By controlled induction of Clink expression, we demonstrated the capacity of the Clink protein to alter RBR function in vivo. We showed that transcription of both S-phase-specific and G(2)/M-phase-specific genes was up-regulated depending on the RBR-binding proficiency of Clink. Concomitantly, ploidy levels increased in a substantial fraction of leaf cell nuclei. Also, leaf epidermis cells of transgenic plants producing Clink were smaller and more numerous, indicating additional cell divisions in this tissue. Furthermore, cytogenetic analyses following induction of Clink expression in mature leaves revealed the presence of metaphasic and anaphasic nuclei, clear evidence that Clink-mediated RBR inactivation is sufficient to induce quiescent cells to reenter cell cycle progression and, for at least a fraction of them, to pass through mitosis. Expression of Clink had no effect on genes transcribed by RNA polymerases I and III, suggesting that, in contrast to its mammalian homologue, A. thaliana RBR is not involved in the repression of polymerase I and polymerase III transcription. The results of these in vivo analyses firmly establish Clink as a member of the diverse class of multifunctional cell cycle modulator proteins encoded by small DNA viruses