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Summary Seasonal changes in spring induce flowering by expressing the florigen, FLOWERING LOCUS T (FT), inArabidopsis.FTis expressed in unique phloem companion cells with unknown characteristics. The question of which genes are co-expressed withFTand whether they have roles in flowering remains elusive. Through tissue-specific translatome analysis, we discovered that under long-day conditions with the natural sunlight red/far-red ratio, theFT-producing cells express a gene encoding FPF1-LIKE PROTEIN 1 (FLP1). The masterFTregulator, CONSTANS (CO), controlsFLP1expression, suggestingFLP1’s involvement in the photoperiod pathway. FLP1 promotes early flowering independently ofFT,is active in the shoot apical meristem, and induces the expression ofSEPALLATA 3(SEP3), a key E-class homeotic gene. Unlike FT, FLP1 facilitates inflorescence stem elongation. Our cumulative evidence indicates that FLP1 may act as a mobile signal. Thus, FLP1 orchestrates floral initiation together with FT and promotes inflorescence stem elongation during reproductive transitions.