The chromosome-scale assembly of endive (Cichorium endivia) genome provides insights into the sesquiterpenoid biosynthesis.

Endive (Cichorium endivia L.) is a leafy vegetable in the Asteraceae family. Sesquiterpene lactones (STLs) in endive leaves bring a bitter taste that varies between varieties. Despite their importance in breeding varieties with unique flavours, sesquiterpenoid biosynthesis pathways in endive are poorly understood. We assembled a chromosome-scale endive genome of 641 Mb with a contig N50 of 5.16 Mb and annotated 46,711 protein-coding genes. Several gene families, especially terpene synthases (TPS) genes, expanded significantly in the C. endivia genome. STLs biosynthesis-related genes and TPS genes in more bitter varieties have shown a higher level of expression, which could be attributed to genomic variations. Our results penetrate the origin and diversity of bitter taste and facilitate the molecular breeding of endive varieties with unique bitter tastes. The high-quality endive assembly would provide a reference genome for studying the evolution and diversity of Asteraceae.

Identification of GROWTH-REGULATING FACTOR transcription factors in lettuce (Lactuca sativa) genome and functional analysis of LsaGRF5 in leaf size regulation.

BACKGROUND: GROWTH-REGULATING FACTORs (GRFs), a type of plant-specific transcription factors, play important roles in regulating plant growth and development. Although GRF gene family has been identified in various plant species, a genome-wide analysis of this family in lettuce (Lactuca sativa L.) has not been reported yet. RESULTS: Here we identified 15 GRF genes in lettuce and performed comprehensive analysis of them, including chromosomal locations, gene structures, and conserved motifs. Through phylogenic analysis, we divided LsaGRFs into six groups. Transactivation assays and subcellular localization of LsaGRF5 showed that this protein is likely to act as a transcriptional factor in the cell nucleus. Furthermore, transgenic lettuce lines overexpressing LsaGRF5 exhibited larger leaves, while smaller leaves were observed in LsaMIR396a overexpression lines, in which LsaGRF5 was down-regulated. CONCLUSIONS: These results in lettuce provide insight into the molecular mechanism of GRF gene family in regulating leaf growth and development and foundational information for genetic improvement of the lettuce variations specialized in leaf character.