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

Abstract

Broccoli (<i>Brassica oleracea</i> var. <i>italica</i> 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 <i>B. oleracea</i> varieties, combined with a phylogenetic tree analysis, sequence alignment, and the construction of a 3D model of the methylthioalkylmalate synthase 1 (MAM1) protein, revealed that the gene copy number and amino acid sequence variation both contributed to the diversity of GSL biosynthesis in <i>B. oleracea</i>. The overexpression of <i>BoMAM1</i> (BolI0108790) in broccoli resulted in high accumulation and a high ratio of C4-GSLs, demonstrating that BoMAM1 is the key enzyme in C4-GSL biosynthesis. These results provide valuable insights for future genetic studies and nutritive component applications of <i>Brassica</i> crops.