Upregulation of a KN1 homolog by transposon insertion promotes leafy head development in lettuce

Significance Heading, which facilitates harvest and contributes to taste and shelf life, is an important trait in some vegetable crops. However, litter is known about its genetic and molecular mechanism. Here, we report the genetic cloning of a key regulator ( LsKN1 ) of heading in lettuce, which is homologous to the knotted 1 ( KN1 ) gene in maize. The LsKN1 gene is upregulated by the insertion of a CACTA-like transposon. Its enhanced expression suppressed the LsAS1 gene and consequently altered leaf polarity and led to a heading phenotype.