Chromosome-scale reference genome of broccoli (Brassica oleracea var. italica Plenck) provides insights into glucosinolate biosynthesis

Abstract Broccoli (Brassica oleracea var. italica Plenck) is an important vegetable crop, as it is rich in health-beneficial glucosinolates (GSLs). However, the genetic basis of the GSL diversity in Brassicaceae remains unclear. Here, we report a chromosome-level genome assembly of broccoli generated using PacBio HiFi reads and Hi-C technology. The final genome assembly is 613.79 Mb in size, with a contig N50 of 14.70 Mb. The GSL profile and content analysis of different Brassicas oleracea varieties, combined with a phylogenetic tree analysis, sequence alignment, and the construction of a three-dimensional model of the methylthioalkylmalate synthase 1 (MAM1) protein, which revealed that the gene copy number and amino acid sequence variation both contributed to the diversity of GSL biosynthesis in Brassica oleracea. The overexpression of BoMAM1 (BolI0108790) in broccoli resulted in high accumulation and a high ratio of C4-GSLs, demonstrating that BoMAM1 is the key enzyme in C4-GSLs biosynthesis. These results provide valuable insights for future genetic studies and nutritive component applications of Brassica crops.