Silencing the conserved small nuclear ribonucleoprotein SmD1 target gene alters susceptibility to root-knot nematodes in plants.

Root-knot nematodes (RKNs) are among the most damaging pests of agricultural crops. Meloidogyne is an extremely polyphagous genus of nematodes that can infect thousands of plant species. A few genes for resistance (R-genes) to RKN suitable for use in crop breeding have been identified, but virulent strains and species of RKN have emerged that render these R-genes ineffective. Secretion of RKN effectors targeting plant functions mediates the reprogramming of root cells into specialized feeding cells, the giant cells, essential for RKN development and reproduction. Conserved targets among plant species define the more relevant strategies for controlling nematode infection. The EFFECTOR18 (EFF18) protein from M. incognita interacts with the spliceosomal small nuclear ribonucleoprotein D1 (SmD1) in Arabidopsis (Arabidopsis thaliana), disrupting its function in alternative splicing regulation and modulating the giant cell transcriptome. We show here that EFF18 is a conserved RKN-specific effector that targets this conserved spliceosomal SmD1 protein in Solanaceae. This interaction modulates alternative splicing events produced by tomato (Solanum lycopersicum) in response to M. incognita infection. The alteration of SmD1 expression by virus-induced gene silencing in Solanaceae affects giant cell formation and nematode development. Thus, our work defines a promising conserved SmD1 target gene to develop broad resistance for the control of Meloidogyne spp. in plants.

Induction of antibiotic specialized metabolism by co-culturing in a collection of phyllosphere bacteria.

A diverse set of bacteria live on the above-ground parts of plants, composing the phyllosphere, and play important roles for plant health. Phyllosphere microbial communities assemble in a predictable manner and diverge from communities colonizing other plant organs or the soil. However, how these communities differ functionally remains obscure. We assembled a collection of 258 bacterial isolates representative of the most abundant taxa of the phyllosphere of Arabidopsis and a shared soil inoculum. We screened the collection for the production of metabolites that inhibit the growth of Gram-positive and Gram-negative bacteria either in isolation or in co-culture. We found that isolates capable of constitutive antibiotic production in monoculture were significantly enriched in the soil fraction. In contrast, the proportion of binary cultures resulting in the production of growth inhibitory compounds differed only marginally between the phyllosphere and soil fractions. This shows that the phyllosphere may be a rich resource for potentially novel molecules with antibiotic activity, but that production or activity is dependent upon induction by external signals or cues. Finally, we describe the isolation of antimicrobial acyloin metabolites from a binary culture of Arabidopsis phyllosphere isolates, which inhibit the growth of clinically relevant Acinetobacter baumannii.

The overlooked manipulation of nucleolar functions by plant pathogen effectors.

Pathogens need to manipulate plant functions to facilitate the invasion of their hosts. They do this by secreting a cocktail of molecules called effectors. Studies of these molecules have mostly focused on the mechanisms underlying their recognition and the subsequent transcriptional reprogramming of cells, particularly in the case of R gene-dependent resistance. However, the roles of these effectors are complex, as they target all cell compartments and their plant targets remain largely uncharacterized. An understanding of the mechanisms involved would be a considerable asset for plant breeding. The nucleolus is the site of many key cellular functions, such as ribosome biogenesis, cellular stress regulation and many other functions that could be targets for pathogenicity. However, little attention has been paid to effectors targeting nucleolar functions. In this review, we aim to fill this gap by providing recent findings on pathogen effectors that target and manipulate nucleolar functions and dynamics to promote infection. In particular, we look at how some effectors hijack ribosome biogenesis, the modulation of transcription or alternative splicing, all key functions occurring at least partially in the nucleolus. By shedding light on the role of the plant nucleolus in pathogen interactions, this review highlights the importance of understanding nucleolar biology in the context of plant immunity and the mechanisms manipulated by plant pathogens.

Cultural flies: Conformist social learning in fruitflies predicts long-lasting mate-choice traditions.

Despite theoretical justification for the evolution of animal culture, empirical evidence for it beyond mammals and birds remains scant, and we still know little about the process of cultural inheritance. In this study, we propose a mechanism-driven definition of animal culture and test it in the fruitfly. We found that fruitflies have five cognitive capacities that enable them to transmit mating preferences culturally across generations, potentially fostering persistent traditions (the main marker of culture) in mating preference. A transmission chain experiment validates a model of the emergence of local traditions, indicating that such social transmission may lead initially neutral traits to become adaptive, hence strongly selecting for copying and conformity. Although this situation was suggested decades ago, it previously had little empirical support.