Biology subjects

Gerhardt, I. R.

Publications and source records attributed to Gerhardt, I. R..

3 recordsLinked to original sources

bioRxiv2026

A haplotype-resolved, near telomere-to-telomere genome assembly of the desiccation-tolerant plant Vellozia tubiflora

Vegetative desiccation tolerance allows plants to survive the loss of up to 95% of their cellular water content and recover upon rehydration. The family Velloziaceae contains the largest number of desiccation-tolerant species among flowering plants, yet genomic resources for this lineage remain extremely limited. Here we report the first reference genome of the genus Vellozia, the most species-rich genus of the family. Using PacBio HiFi sequencing and Omni-C chromatin conformation data, we generated a haplotype-resolved genome assembly of Vellozia tubiflora with near telomere-to-telomere continuity. Hap1 and Hap2 span 423.2 Mb and 426.4 Mb, respectively, with both assemblies successfully anchored into nine chromosome-length scaffolds. The former presents a scaffold N50 of 49.8 Mb and 96.5% BUSCO completeness, while the latter reaches 50.0 Mb and 96.8%. Genome annotation predicted 23,352 and 23,549 protein-coding genes in Hap1 and Hap2, respectively. This resource is anticipated to foster new insights for comparative and evolutionary studies of vegetative desiccation tolerance across angiosperms and expands the genomic representation of plants from the Brazilian campos rupestres, a threatened biodiversity hotspot characterized by extreme environmental conditions.

plant biology↗

bioRxiv2024

Revisiting the cytogenetics of Vellozia Vand.: immunolocalization of KLN1 elucidates the chromosome number for the genus

Chromosome number is the most fundamental trait of a karyotype. Accurate chromosome counting is essential for further analyses including cytogenomics, taxonomic, evolutionary, and genomic studies. Despite its importance, miscounting is common, especially in early publications on species with small and morphologically similar chromosomes. Vellozia Vand. is a genus mainly distributed throughout South America belonging to the angiosperm family Velloziaceae, a dominant taxon in the Brazilian "campos rupestres". Cytogenetic studies within the group have been rare and have shown conflicting chromosome counts, even within the same species. These discrepancies are associated with the presence of a few small chromosome-like structures, which were previously classified as possible satellites. Here, to accurately determine the chromosome number of species belonging to the genus, we used different cytogenomics approaches, including the immunostaining of the KNL1 kinetochore protein combined with chromosome spread preparation using tissue culture-derived samples. Our results revealed 2n = 18 chromosomes for all six species studied. This finding suggests that the basic chromosome number for Vellozia is x = 9 and not x = 8, as previously proposed. The immunolocalization of functional centromeres was fundamental for undoubtedly identifying the smaller chromosome pair as real chromosomes and accurately determining the correct chromosome number of these species. This will provide substantial support for further studies, including investigations into karyotype evolution and the generation of reference genomes for the species of the family.

plant biology↗

bioRxiv2021

Plant-associated microbiomes promote nutrient turnover in impoverished substrates of a biodiversity hotspot

The substrates of the Brazilian campos rupestres have extremely low concentrations of key nutrients, mainly phosphorus, imposing severe restrictions to plant growth. Regardless, this ecosystem harbors enormous biodiversity which raises the question of how nutrients are cycled and acquired by the biosphere. To uncover the nutrient turnover potential of plant-associated microorganisms in the campos rupestres, we investigated the compositions and functions of microbiomes associated with two species of the Velloziaceae family that grow over distinct substrates (soil and rock). Amplicon, metagenomic, and metagenome-assembled genome sequence data showed that the campos rupestres harbor a novel assemblage of plant-associated prokaryotes and fungi. Compositional analysis revealed that the plant-associated soil and rock communities differed in taxonomic structure but shared a core of highly efficient colonizers that were strongly coupled with nutrient mobilization. Investigation of functional and abundance data revealed that the plant hosts actively recruit communities by exuding organic compounds and that the root-associated microbiomes possess a diverse repertoire of phosphorus turnover mechanisms. We also showed that the microbiomes of both plant species encompass novel populations capable of mobilizing nitrogen and that the substrate strongly influences the dynamics of this cycle. Our results show that the interplay between plants and their microbiomes shapes nutrient turnover in the campos rupestres. We highlight that investigation of microbial diversity is fundamental to understand plant fitness in stressful environments.

genomics↗