Characterisation of transcriptomic profiles for high glucoraphanin broccoli lines

RNA-sequencing was performed to characterise the transcriptomic profiles of a series of glucoraphanin variant broccoli lines. The aim is to study how the different allelic composition in broccoli influences the expression levels of genes involved in the aliphatic glucosinolate biosynthesis pathway, known in studies in the model plant Arabidopsis thaliana to be regulated by the R2R3 MYB transcription factor MYB28. MYB28 genotype is associated with higher accumulation levels of the aliphatic glucosinolate, glucoraphanin, reflecting whether the line is heterozygous or homozygous for the introgression of a MYB28 allele from the wild Brassica, Brassica villosa. RNA-sequencing data was analysed to compare the transcriptional profile of leaves from field-grown broccoli lines with contrasting MYB28 genotypes. When compared to standard broccoli, leaf tissue of the broccoli line homozygous for the introgression of the MYB28v allele from Brassica villosa shows up-regulation of genes involved in the aliphatic glucosinolate biosynthesis pathway, including amino acid side-chain elongation and core structure biosynthesis. This correlates with the significant increase in glucoraphanin accumulation found in this tissue in the field.