Abstract
Many plants are incapable of flowering in inductive daylengths during the early juvenile vegetative phase (JVP). Arabidopsis mutants with reduced expression of TEMPRANILLO (TEM), a repressor of FLOWERING LOCUS T (FT) had a shorter JVP than wild-type plants. Reciprocal changes in mRNA expression of TEM and FT were observed in both Arabidopsis and antirrhinum, which correlated with the length of the JVP. FT expression was induced just prior to the end of the JVP and levels of TEM1 mRNA declined rapidly at the time when FT mRNA levels were shown to increase. TEM orthologs were isolated from antirrhinum (AmTEM) and olive (OeTEM) and were expressed most highly during their juvenile phase. AmTEM functionally complemented AtTEM1 in the tem1 mutant and over-expression of AmTEM prolonged the JVP through repression of FT and CONSTANS (CO). We propose that TEM may have a general role in regulating JVP in herbaceous and woody species.
Highlights
Many plants are incapable of flowering in inductive daylengths during the early juvenile vegetative phase (JVP)
Assessment of flowering times in Arabidopsis plants transferred from LDs to short days (SD) at daily intervals from germination showed that the JVP lasted for 6.8 6 0.2 d after germination in Col-0 wild-type plants, compared to 4.06 6 0.35 d in the tem[1] single mutant and 20.5 6 0.2 d, in the RNAi-tem1/2 double mutant (Fig. 1a–c)
Using transfer experiments from LD to SD we found that the JVP in the Arabidopsis ecotype Col-0 lasts for about 6–7 days
Summary
Many plants are incapable of flowering in inductive daylengths during the early juvenile vegetative phase (JVP). In the early stages some plants are incapable of initiating flowering, even when grown under favourable environmental conditions This is known as the juvenile vegetative phase (JVP), which precedes the adult vegetative phase (AVP), in which reproductive competence is established and the plant can respond to inductive conditions. Initiation of the reproductive phase is regulated by an elaborate network of floral signalling pathways, which include the photoperiodic, vernalization, autonomous, light-quality and ambient temperature pathways[8,9]. These regulate expression of the FLOWERING LOCUS T (FT) gene. The fact that plants are incapable of initiating flowering during juvenility even when environmental growth conditions are conducive suggests that inhibitory mechanisms may suppress induction of FT during juvenility and prevent premature flowering
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