show Abstracthide AbstractLettuce has been cultivated throughout the year, and traditionally grown outdoors except for butterhead lettuce. For cool-season vegetables such as lettuce, environmental factors, especially heat stress are negatively effect on yield and quality. Accordingly, for stable production for hot-season, higher temperature adaptability is critical trait for lettuce cultivars. Crisphead lettuce has two types, empire type and salinas type. The empire type has deeply serrated undulation leaf with very crisp, and the salinas type has wavy leaf with softer texture. The serrated undulation leaf of empire type was clearly associated with high incidence of tipburn disorder. Tipburn is a complex and unpredictable disorder that involves a collapse and necrosis of the apex and margins of actively growing leaves, which occurs under warm growing conditions. We performed transcriptome analysis to investigate gene associated with leaf marginal serration.