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Cabbage has significant heterosis and most commercial cultivars are hybrids. To explore genetic basis of cabbage heterosis and promote cabbage heterosis utilization, we constructed two populations by crossing 100 DH lines derived from a cabbage hybrid 01-20 ×96-100 with two female parents. Hybrids exhibited different extents of heterosis, the mean value of economic yield was 2.6 times bigger than parents. We identified 66 and 73 QTLs associated with mid-parent heterosis and transgressive heterosis of twelve yield-related traits, respectively. Some QTLs could be detected under the two-year experiment existed in two populations with different testers, showing relatively high phenotypic contribution rate (15.8%-20.0%). Heterosis QTLs exhibited clustered distribution in several cabbage chromosome regions. Two dominant genetic regions, mk300-316 and mk258-268, originated from the elite parent 01-20, exhibited significant genetic effects for yield-related heterosis, which were first identified. Three elite DH lines (D22, D46, D83) harboring these two dominant regions were selected as having strong heterosis in cabbage production. Candidate gene analysis revealed that some genes participating in biosynthetic processes of carbohydrates and some responses to auxin might affect cabbage yield heterosis. QTL identification and genetic dissection of yield-related traits provide new insights into the genetic effects of cabbage heterosis. [ABSTRACT FROM AUTHOR]

The insufficient supply of sugar units is the key limitation for the biosynthesis of glycosylated products. The unusual sugar TDP-L-mycarose is initially attached to the C3 of the polyketide erythronolide B, resulting in 3-O-a-mycarosylerythronolide B (MEB). Here, we present the de novo biosynthesis of MEB in Escherichia coli and improve its production using multi-strategy metabolic engineering. Firstly, by blocking precursor glucose-1-phosphate competing pathways, the MEB titer of triple knockout strain QC13 was significantly enhanced to 41.2 mg/L, 9.8-fold to that produced by parental strain BAP230. Subsequently, the MEB production was further increased to 48.3 mg/L through overexpression of rfbA and rfbB. Moreover, the CRISPRi was implemented to promote the TDP-L-mycarose biosynthesis via repressing the glycolysis and TDP-L-rhamnose pathway. Our study paves the way for efficient production of erythromycins in E. coli and provides a promising platform that can be applied for biosynthesis of other glycosylated products with unusual sugars. [ABSTRACT FROM AUTHOR]