Biology subjects

Richter, R.

Publications and source records attributed to Richter, R..

21 records · Page 2Linked to original sources

bioRxiv2020

Same same but different: Cluster architecture variation in five 'Pinot Noir' selection lines correlates with differential expression of three transcription factors and further growth related genes

Grapevine (Vitis vinifera L.) is an economically important crop that needs to comply with high quality standards for fruit, juice and wine production. Intense plant protection is required to avoid losses caused by fungal infections. Grapevine cultivars with loose cluster architecture enable to reduce protective chemical treatments due to their enhanced resilience against fungal infections such as Botrytis cinerea induced grey mold. A recent study identified transcription factor gene VvGRF4 as determinant of inflorescence structure in exemplary samples of loose and compact quasi-isogenic Pinot Noir clones. Here, we extended the analysis to 12 differently clustered Pinot Noir clones originating from five different clonal selection programs. Differential gene expression of these clones was studied in three different locations over three seasons in demonstrative vineyards. Two phenotypically contrasting clones were grown at all three locations and served for standardization of downstream analyses. Differential gene expression data were correlated to the phenotypic variation of cluster architecture sub-traits. A consistent differential gene expression of VvGRF4 in relation to loose clusters was verified over the different environments and in the extended set of Pinot Noir clones. In addition, 14 more genes with consistent expression differences between loosely and compactly clustered clones independent from season and location were identified. These genes show annotations related to cellular growth, cell wall extension, cell division and auxin metabolism. They include two more transcription factor genes.

plant biology↗

bioRxiv2020

Canopy position has a stronger effect than tree species identity on phyllosphere bacterial diversity in a floodplain hardwood forest

The phyllosphere is a challenging microbial habitat in which microorganisms can flourish on organic carbon released by plant leaves but are also exposed to harsh environmental conditions. Here, we assessed the relative importance of canopy position - top, mid, and bottom at a height between 31 m and 20 m - and tree species identity for shaping the phyllosphere microbiome in a floodplain hardwood forest. Leaf material was sampled from three tree species - maple (Acer pseudoplatanus L.), oak (Quercus robur L.), and lime (Tilia cordata MILL.) - at the Leipzig canopy crane facility (Germany). Estimated bacterial species richness (Chao1) and bacterial abundances approximated by quantitative PCR of 16S rRNA genes exhibited clear vertical trends with a strong increase from the top to the mid and bottom position of the canopy. 30 Operational Taxonomic Units (OTUs) formed the core microbiome, which accounted for 77% of all sequence reads. These core OTUs showed contrasting trends in their vertical distribution within the canopy, pointing to different ecological preferences and tolerance to presumably more extreme conditions at the top position of the canopy. Co-occurrence analysis revealed distinct tree species-specific OTU networks, and 55-57% of the OTUs were unique to each tree species. Overall, the phyllosphere microbiome harbored surprisingly high fractions of Actinobacteria of up to 46%. Our results clearly demonstrate strong effects of the position in the canopy on phyllosphere bacterial communities in a floodplain hardwood forest and - in contrast to other temperate or tropical forests - a strong predominance of Actinobacteria.

microbiology↗

bioRxiv2020

Tree crowns as meeting points of diversity generating mechanisms - a test with epiphytic lichens in a temperate forest

Forest canopies are hotspots of biodiversity even in temperate forests but which and how many ecological mechanisms contribute to the high diversity remains elusive. This biodiversity is not distributed evenly throughout the complex fractal structures formed by individual tree crowns. They are non-stationary, constantly expose new surface habitat via growth, and create contrasting abiotic conditions. These features give rise to a range of vertical gradients in habitat optimality, heterogeneity, available surface area and time for succession - all known to be mechanisms shaping diversity patterns. Using a canopy crane facility and epiphytic lichens on Fraxinus excelsior and Quercus robur as model system, we aim to assess the relative importance as well as the interplay of these mechanisms in shaping biodiversity patterns within tree canopies by detecting their distinct mechanistic fingerprints. Lichen species richness exhibited a hump-shaped vertical pattern, skewed towards the top of the crown. This pattern was observable at both the level of individual plots and that of aggregate height layers and it was correlated with lichen cover. Also, a vertical gradient in species composition was found and could be related to species traits known to reflect successional niches such as dispersal mode and growth form. Habitat heterogeneity and available surface area have been found to have little effect on vertical lichen diversity patterns. We conclude that the vertical lichen diversity patterns in the tree crown are mainly shaped by the successional accumulation of species along a branch age gradient and a pronounced vertical gradient in environmental optimality from harshly exposed young branches at the top crown over suitable habitats with a balance in light and humidity towards the limiting light conditions in the dim understory. At the level of the whole canopy, successional and environmental niche dynamics jointly operate to generate lichen diversity.

ecology↗