Melina Sophie Nowak

Summary: Here, we present a comprehensive multiomics analysis of anthocyanin biosynthesis in Rubus armeniacus , known for its dark fruits. A phased genome sequence of the tetraploid blackberry was generated, achieving an N50 of 34 Mb with an assembly size of 1.2 Gbp based on Oxford Nanopore Technology sequencing (ONT). The BUSCO score for the total assembly shows a high completeness of 99.1%. The assembly was separated into 4 pseudohaplophases, with the pseudohaplophase A representing the R. armeniacus genome in 7 chromosome scale contigs, with an N50 of 46 Mbp and 98.8% conserved BUSCO genes. A total of 118,183 protein coding genes were annotated within the genome assembly and all relevant genes encoding enzymes and transcriptional regulators of the anthocyanin biosynthesis pathway were identified within each pseudohaplophase. To further understand the underlying cause of dark pigmentation, the gene expression was analysed during different stages of berry development revealing a strong induction of anthocyanin biosynthesis genes including the anthocyanin activating subgroup 6 MYB transcriptions during the berry ripening process. Further, a quantification of cyanidin-3-O-glucoside in methanolic berry extract, utilizing a UHPLC-HRAM-MS analysis, revealed an approximately 500-fold increase of cyanidin-3-O-glucoside from green to black fruit, indicating that dark pigmentation in R. armeniacus results from high anthocyanin accumulation. Significance statement: This study provides a multiomics analysis of the dark pigmentation of Rubus armeniacus, including a high quality phased assembly and an in-depth analysis of the anthocyanin biosynthesis pathway. A transcriptional and metabolomic analysis revealed that dark berry pigmentation is caused by a high accumulation of cyanidin-3-O-glucoside during fruit ripening.

Access to genome sequences is crucial to investigate and engineer traits in plants, explore biodiversity, and support phylogenetic studies. During the last decade, affordable sequencing devices have substantially increased the size of the genomics community by enabling individual research groups to sequence the genomes of their favourite plants. There has also been a quick development of novel tools for sequencing data analysis. Here, we share experiences with plant long-read genomics methods for Oxford Nanopore Technologies (ONT) and provide hands-on guidelines to support newcomers’ dive into plant genomics. The full workflow from planning a plant genome sequencing project to public release of associated data sets is covered.

Victoria cruziana is well known for its huge floating leaves covered with sharp spines and its night blooming. Reports indicate that white flowers open during the first night and turn light pinkish during the following day and the second night. Here, we set out to unravel the molecular basis and ecological function of the flower color change in V. cruziana . A high quality genome sequence with a contig N50 of 44.2 Mbp, a scaffold N50 of 300 Mbp, and a total assembly size of 3.5 Gbp was generated as the genetic basis for this study. Comparative transcriptomics revealed the genes required for anthocyanin biosynthesis genes and their transcriptional regulators as differentially expressed between the white and the light pinkish stage of a flower. Structural genes with expression differences between white and light pinkish flower stages include VcrF3’H , VcrF3’5’H , VcrDFR , VcrANS , and VcrarGST . The expression pattern of the corresponding transcription factors VcrMYB123 , VcrMYB-SG6_a , VcrMYB-SG6_b, VcrTT8 , and VcrTTG1 also showed differences that aligned with the flower color.