Characterization and identification of OsFTL8 gene in rice

The rice genome contains 13 Flowering Locus T-Like ( FT-Like ) genes, among which, OsFTL2 / Hd3a and OsFTL3/RFT1 are characterized as florigen-encoding genes, promoting rice flowering under short-day and long-day conditions, respectively. However, the functions of the other FT-Like members are still unknown in rice. In this study, we characterized and identified a member of FT-Like family, OsFTL8 gene. The investigation of photoperiodic expression pattern showed that OsFTL8 transcription was mainly induced under short-day conditions. The qRT-PCR and GUS staining assays indicated that OsFTL8 was broadly expressed in various organs, including stems, leaves and panicles. OsFTL8 overexpression transgenic lines and its knockout mutants displayed no obvious change in their heading date, compared with the wild type. However, the pollen viability and seed setting rate were decreased in the overexpression transgenic lines. OsFTL8 localizes in both nucleus and cytoplasm. And we found that OsFTL8 does not interact with OsFD1 in vivo, suggesting that OsFTL8 may not be the component of florigen activation complex (FAC). In summary, our results indicate that OsFTL8 is associated with pollen viability and not involved in regulating rice flowering time, implying functional divergence of FT-Like members.