LsARF3 mediates thermally induced bolting through promoting the expression of in lettuce ( L.).

Lettuce ( L.) is a leafy vegetable whose edible organs usually are leaf or stems, and thus high-temperature induced bolting followed by flower initiation is an undesirable trait in lettuce production. However, the molecular mechanism that controls lettuce bolting and flowering upon thermal treatments is largely unknown. Here, we identified a Lettuce (), the expression of which was enhanced by heat and auxin treatments. Interestingly, is preferentially expressed in stem apex, suggesting it might be associated with lettuce bolting. Transgenic lettuce overexpressing displayed early bolting and flowering, whereas knockout of dramatically delayed bolting and flowering in lettuce under normal or high temperature conditions. Furthermore, Exogenous application of IAA failed to rescue the late-bolting and -flowering phenotype of mutants. Several floral integrator genes including , , and were co-expressed with in the overexpression and knockout lettuce plants. Yeast one-hybrid (Y1H) experiments suggested that LsARF3 could physically interact with the promoter, which was further confirmed by a dual luciferase assay in tobacco leaves. The results indicated that LsARF3 might directly modulate the expression of in lettuce. Therefore, these results demonstrate that could promote lettuce bolting in response to the high temperature by directly or indirectly activating the expression of floral genes such as which provides new insights into lettuce bolting in the context of ARFs signaling and heat response.