Biology subjects

Mumm, R.

Publications and source records attributed to Mumm, R..

4 recordsLinked to original sources

bioRxiv2026

Same visitors, different outcomes: floral phenotype gates pollinator-vectored nectar microbial establishment

The microbiome of nectar has the potential to modify flower chemistry and plant-pollinator interactions. How its assembly differs between diurnal and nocturnal guilds, and how it depends on the flower they visit, remains poorly resolved in crops. We conducted field assays using two commercial sunflower cultivars (Helianthus annuus) that differ markedly in nectar volume and sugar composition, under four pollinator access treatments. Diurnal pollinator access, whether continuous or daytime-only, resulted in a cultivar-dependent microbiome signature. In one cultivar, nectar communities were characterized by the dominance of specialist taxa such as the yeast Metschnikowia and the bacterium Acinetobacter. However, neither taxa established dominance in the nectar of the other cultivar despite receiving substantial insect visits. Instead, continuous access alone lowered overall fungal diversity without restructuring composition, which was more strongly structured by inter-annual variation than by pollinator access treatment. Profiling of the volatile organic compounds in florets revealed clear differences between cultivars, but different access treatment induced only minor changes in the volatile blends. Our findings establish that pollinator guilds shape sunflower nectar microbiota in a genotype-dependent manner. We propose that diurnal insect visits seed nectar with specialist taxa, but whether those specialists establish depends on nectar availability and composition.

microbiology↗

bioRxiv2023

Functional copy number variation in SQUALENE EPOXIDASE-LIKE genes affects photosystem II efficiency in Arabidopsis

In this study, we found a single quantitative trait locus for photosystem II efficiency ({Phi}PSII) in the Arabidopsis Ler-0 x Col-0 recombinant inbred line population. This locus on chromosome 5 is caused by genetic variation in a cluster of tandemly repeated SQUALENE EPOXIDASE-LIKE (SQE-like) genes, with unknown function. We show the QTL is caused by variation in the SQE5, SQE6 and SQE7 genes affecting {Phi}PSII in a dose-dependent manner, due to a combination of functional copies. Col-0 carries only one functional copy, SQE5, while Ler-0 carries functional copies of SQE6 and SQE7. Overexpression of a functional copy of SQE6 enhances {Phi}PSII to exceed that of the Ler-0 parent in Arabidopsis, but does not affect {Phi}PSII in tobacco. Phylogenetic analysis of the SQE and SQE-likes in 135 plant species revealed that the SQE-likes are evolutionary confined to two sister families, the Cleomaceae and Brassicaceae, and diversified independently. The tandem cluster of four SQE-like genes in Arabidopsis is likely the result of two recent gene duplication events, one generating SQE5 from SQE4, the next one generating SQE6 and SQE7 from SQE5. The involvement of SQE-like genes in photosynthesis will open up new avenues to determine the function of these novel genes.

plant biology↗

bioRxiv2021

Local adaptation shapes metabolic diversity in the global population of Arabidopsis thaliana

The biosynthesis, structure and accumulation of secondary metabolites in plants are largely controlled by genetic factors, which can vary substantially among genotypes within a species. Here we studied a global population of Arabidopsis thaliana accessions for qualitative and quantitative variation in volatile and non-volatile secondary metabolites using essentially untargeted metabolomics. Genome-wide association (GWA) mapping revealed that metabolic variation mainly traces back to genetic variation in dedicated biosynthesis genes. Effect sizes of genetic variants, estimated by a Bayesian procedure, indicate that most of the genetic variation in the accumulation of secondary metabolites is explained by large-effect genes and defined by multiple polymorphisms. The various genetic variants resulted from independent mutation events and combined into distinctive haplotypes, which are representative for specific geographical regions. A strong relationship between the effect-size of regulatory loci, their allele frequencies and fixation index indicates that selection forces discriminate between haplotypes, resulting in different phytochemical profiles. Finally, we demonstrate that haplotype frequencies deviate from neutral theory predictions, suggesting that metabolic profiles are shaped by local adaptation and co-evolution of independent loci.

genetics↗

bioRxiv2018

Reciprocal cybrids reveal how organellar genomes affect plant phenotypes

Assessing the impact of variation in chloroplast and mitochondrial DNA (collectively termed the plasmotype) on plant phenotypes is challenging due to the difficulty in separating their effect from nuclear derived variation (the nucleotype). Haploid inducer lines can be used as efficient plasmotype donors to generate new plasmotype-nucleotype combinations (cybrids)(Ravi et al., 2014). We generated a panel comprising all possible cybrids of seven Arabidopsis thaliana accessions and extensively phenotyped these lines for 1859 phenotypes under stable and fluctuating conditions. We show that natural variation in the plasmotype results in additive as well as epistatic effects across all phenotypic categories. Plasmotypes which induce more additive phenotypic changes also cause more significant epistatic effects, suggesting a possible common basis for both additive and epistatic effects. On average epistatic interactions explained twice as much of the variance in phenotypes as additive plasmotype effects. The impact of plasmotypic variation was also more pronounced under fluctuating and stressful environmental conditions. Thus, the phenotypic impact of variation in plasmotypes is the outcome of multilevel Nucleotype X Plasmotype X Environment interactions and, as such, the plasmotype is likely to serve as a reservoir of variation which is only exposed under certain conditions. The production of cybrids using haploid inducers is a quick and precise method for assessing the phenotypic effects of natural variation in organellar genomes. It will facilitate efficient screening of unique nucleotype-plasmotype combinations to both improve our understanding of natural variation in nucleotype plasmotype interactions and identify favourable combinations to improve plant performance.

genetics↗