It takes three to tango: citizen, fundamental and applied science.

Citizen science is an undervalued tool in a scientist's toolbox with the potential to go beyond primary data collection to strengthen fundamental and applied science. We call for the integration of these three disciplines to make agriculture sustainable and adaptive to climate change, with North-Western European soybean cultivation as showcase.

Opposing effects of trans- and cis-cinnamic acid during rice coleoptile elongation.

The phenylpropanoid cinnamic acid (CA) is a plant metabolite that can occur under a trans- or cis-form. In contrast to the proven bioactivity of the cis-form (c-CA), the activity of trans-CA (t-CA) is still a matter of debate. We tested both compounds using a submerged rice coleoptile assay and demonstrated that they have opposite effects on cell elongation. Notably, in the tip of rice coleoptile t-CA showed an inhibiting and c-CA a stimulating activity. By combining transcriptomics and (untargeted) metabolomics with activity assays and genetic and pharmacological experiments, we aimed to explain the underlying mechanistic processes. We propose a model in which c-CA treatment activates proton pumps and stimulates acidification of the apoplast, which in turn leads to the loosening of the cell wall, necessary for elongation. We hypothesize that c-CA also inactivates auxin efflux transporters, which might cause a local auxin accumulation in the tip of the coleoptile. For t-CA, the phenotype can partially be explained by a stimulation of cell wall polysaccharide feruloylation, leading to a more rigid cell wall. Metabolite profiling also demonstrated that salicylic acid (SA) derivatives are increased upon t-CA treatment. As SA is a known antagonist of auxin, the shift in SA homeostasis provides an additional explanation of the observed t-CA-mediated restriction on cell growth.

Flemish soils contain rhizobia partners for Northwestern Europe-adapted soybean cultivars.

In Europe, soybean (Glycine max) used for food and feed has to be imported, causing negative socioeconomic and environmental impacts. To increase the local production, breeding generated varieties that grow in colder climates, but the yield using the commercial inoculants is not satisfactory in Belgium because of variable nodulation efficiencies. To look for indigenous nodulating strains possibly adapted to the local environment, we initiated a nodulation trap by growing early-maturing cultivars under natural and greenhouse conditions in 107 garden soils in Flanders. Nodules occurred in 18 and 21 soils in the garden and greenhouse experiments respectively. By combining 16S rRNA PCR on single isolates with HiSeq 16S metabarcoding on nodules, we found a large bacterial richness and diversity from different soils. Furthermore, using Oxford Nanopore Technologies sequencing of DNA from one nodule, we retrieved the entire genome of a Bradyrhizobium species, not previously isolated, but profusely present in that nodule. These data highlight the need of combining diverse identification techniques to capture the true nodule rhizobial community. Eight selected rhizobial isolates were subdivided by whole-genome analysis in three genera containing six genetically distinct species that, except for two, aligned with known type strains and were all able to nodulate soybean in the laboratory.

Development of a novel and rapid phenotype-based screening method to assess rice seedling growth.

BACKGROUND: Rice (Oryza sativa) is one of the most important model crops in plant research. Despite its considerable advantages, (phenotypic) bioassays for rice are not as well developed as for Arabidopsis thaliana. Here, we present a phenotype-based screening method to study shoot-related parameters of rice seedlings via an automated computer analysis. RESULTS: The phenotype-based screening method was validated by testing several compounds in pharmacological experiments that interfered with hormone homeostasis, confirming that the assay was consistent with regard to the anticipated plant growth regulation and revealing the robustness of the set-up in terms of reproducibility. Moreover, abiotic stress tests using NaCl and DCMU, an electron transport blocker during the light dependent reactions of photosynthesis, confirmed the validity of the new method for a wide range of applications. Next, this method was used to screen the impact of semi-purified fractions of marine invertebrates on the initial stages of rice seedling growth. Certain fractions clearly stimulated growth, whereas others inhibited it, especially in the root, illustrating the possible applications of this novel, robust, and fast phenotype-based screening method for rice. CONCLUSIONS: The validated phenotype-based and cost-efficient screening method allows a quick and proper analysis of shoot growth and requires only small volumes of compounds and media. As a result, this method could potentially be used for a whole range of applications, ranging from discovery of novel biostimulants, plant growth regulators, and plant growth-promoting bacteria to analysis of CRISPR knockouts, molecular plant breeding, genome-wide association, and phytotoxicity studies. The assay system described here can contribute to a better understanding of plant development in general.

Author Correction: RSPO2 inhibition of RNF43 and ZNRF3 governs limb development independently of LGR4/5/6.

In this Letter, the surname of author Lena Vlaminck was misspelled 'Vlaeminck'. In addition, author Kris Vleminckx should have been associated with affiliation 16 (Center for Medical Genetics, Ghent University, Ghent, Belgium). These have been corrected online.

RSPO2 inhibition of RNF43 and ZNRF3 governs limb development independently of LGR4/5/6.

The four R-spondin secreted ligands (RSPO1-RSPO4) act via their cognate LGR4, LGR5 and LGR6 receptors to amplify WNT signalling1-3. Here we report an allelic series of recessive RSPO2 mutations in humans that cause tetra-amelia syndrome, which is characterized by lung aplasia and a total absence of the four limbs. Functional studies revealed impaired binding to the LGR4/5/6 receptors and the RNF43 and ZNRF3 transmembrane ligases, and reduced WNT potentiation, which correlated with allele severity. Unexpectedly, however, the triple and ubiquitous knockout of Lgr4, Lgr5 and Lgr6 in mice did not recapitulate the known Rspo2 or Rspo3 loss-of-function phenotypes. Moreover, endogenous depletion or addition of exogenous RSPO2 or RSPO3 in triple-knockout Lgr4/5/6 cells could still affect WNT responsiveness. Instead, we found that the concurrent deletion of rnf43 and znrf3 in Xenopus embryos was sufficient to trigger the outgrowth of supernumerary limbs. Our results establish that RSPO2, without the LGR4/5/6 receptors, serves as a direct antagonistic ligand to RNF43 and ZNRF3, which together constitute a master switch that governs limb specification. These findings have direct implications for regenerative medicine and WNT-associated cancers.