Sugar Beet Root Development Transcriptome

Sugar beet (Beta vulgaris) roots undergo a developmental phase change at 5-weeks post emergence under greenhouse conditions. This phase change coincides with the development of defined conical rings composed of parenchyma and vasculature tissue, competency to accumulate sucrose, high biomass accumulation, and onset of adult-phase root disease resistance. RNAseq was performed on sugar beet germplasm ‘C869’ spanning this developmental stage, at weekly intervals from 3- to 10-weeks post emergence. Phenotypically, root development occurred in a similar manner as previously seen, with average (n=10) root biomass increasing from 2 mg at 3-weeks to 3.2 g at 10-weeks. Transcriptomes from 3- to 7-weeks, plus another at 10-weeks, were obtained from a single Illumina HiSeq 2000 lane using adapter barcoded samples. After processing the reads, 240 million high quality reads were obtained, (25 – 50 million per sample). Preliminary analyses using reads mapping to the C869UK genome assembly (version 0.1), found 92 significant genes differentially expressed across consecutive weeks of development. Genes from the entire root development transcriptome were annotated and predicted to have diverse functions i.e. hormone response (auxin, gibberellin, jasmonate), cell wall patterning (cellulose synthase-like, cell wall associated hydrolases, expansin), and transcriptional regulation. Comparative analysis is currently underway to characterize the variability in root development, as well as the relationships between sucrose accumulation, gene expression and developmental phase that will ultimately assist in breeding more productive sugar beets.