Abstract
Photoperiod is a crucial inducer of plant flowering. Cycling DOF factors (CDFs) play pivotal roles in the flowering of long-day (LD) and short-day (SD) plants. However, the functions of CDFs in the photoperiod regulated flowering remain unclear in day-neutral plants. In the present study, tomato (Solanum lycopersicum L. cv. “Ailsa Craig”) seedlings of the wild-type and transgenic lines of overexpressing CDFs were treated with different photoperiods. The flowering time and the expression pattern of SlCDFs and other FT-like genes were investigated. The results showed that tomato SlCDF1, SlCDF2, SlCDF3, SlCDF4, and SlCDF5 are homologs to Arabidopsis cycling DOF factor 1 (AtCDF1). SlCDF1–5 expression levels were influenced by the developmental stage and the tissue location, and notably, the expression patterns throughout light environments showed two opposite trends. Among the SlCDF1–5 overexpression transgenic lines, overexpressing SlCDF3 delayed flowering time in both LD (16 h light/8 h dark) and SD (8 h light/16 h dark) conditions. Furthermore, SlCDF3 led to an increase in the mRNA level of SlSP5G, a tomato FT-like gene, in LD conditions, while the transcription level of the other two FT-like genes, SlSP5G2 and SlSP5G3, were up-regulated in SD conditions. Taken together, at the transcription level, our results demonstrated that SlCDF3 played a significant role in controlling tomato flowering under LD and SD conditions, possibly through directly or indirectly regulating FT-like genes.
Highlights
Light is one of the most important factors in plant growth and development, since light is the driving force of photosynthesis but acts as an important transduction signal to regulate photomorphogenesis and endogenous substance metabolism via triggering or repressing related gene expressions (Ma et al, 2001)
We constructed a phylogenetic tree based on the amino acid sequences of 36 Arabidopsis DOF and 34 tomato DOF proteins, finding that SlCDF1–5 in tomato were closely related to AtCDF1–5 (Supplementary Figure 1)
Our present study demonstrated that SlCDF3 played an important role in the regulation of tomato flowering via inducing the expression of the downstream flowering locus T (FT)-like genes directly or indirectly
Summary
Light is one of the most important factors in plant growth and development, since light is the driving force of photosynthesis but acts as an important transduction signal to regulate photomorphogenesis and endogenous substance metabolism via triggering or repressing related gene expressions (Ma et al, 2001). SlCDF3 Regulates Tomato Flowering flowering time of tomato is delayed under LD conditions and promoted under short day (SD) conditions (Sawhney and Greyson, 1972). In Arabidopsis, flowering locus T (FT) encodes florigen, a key protein in triggering flowering, and its transcription is regulated by photoperiods (Kobayashi et al, 1999). Flavin Kelch Box (FKF1), Gigantea (GI), and constans (CO) function as transcriptional activators, whereas short vegetative phase (SVP), flowering loucs C (FLC), tempranillo (TEM), and cycling DOF factor 1 (CDF1) function as transcriptional repressors (Andrés and Coupland, 2012). There are five CDF genes (AtCDF1–5) in Arabidopsis and overexpression of AtCDF1 results in flowering delay (Song et al, 2012). Subsequent studies have revealed that OsDof and OsDof are in the same subfamily, with similar functions in photoperiod-regulated flowering (Wu et al, 2017)
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