Mobility of Antiflorigen and PEBP mRNAs in Tomato-Tobacco Heterografts.

Photoperiodic floral induction is controlled by the leaf-derived and antagonistic mobile signals florigen and antiflorigen. In response to photoperiodic variations, florigen and antiflorigen are produced in leaves and translocated through phloem to the apex, where they counteract floral initiation. Florigen and antiflorigen are encoded by a pair of homologs belonging to ()- or ()-like clades in the phosphatidylethanolamine-binding domain protein (PEBP) family. The PEBP gene family contains -, -, and ()-like clades. Evolutionary analysis suggests that - and -like clades arose from an ancient -like clade. The protein movement of the PEBP family is an evolutionarily conserved mechanism in many plants; however, the mRNA movement of the PEBP family remains controversial. Here, we examined the mRNA movement of PEBP genes in different plant species. We identified a tobacco () gene, denoted , and showed that is an ortholog of the Arabidopsis () antiflorigen In tobacco, acts as a mobile molecule that non-cell-autonomously inhibits flowering. Grafting experiments showed that endogenous and ectopically expressed mRNAs move long distances in tobacco and Arabidopsis. Heterografts of tobacco and tomato () showed that, in addition to , multiple members of the -, -, and -like clades of tobacco and tomato PEBP gene families are mobile mRNAs. Our results suggest that the mRNA mobility is a common feature of the three clades of PEBP-like genes among different plant species.