1. Introduction
In the life cycle of plant, the flower development is a vital checkpoint
at which shoot apical meristem (SAM) stops producing vegetative growth
and starts to produce reproductive growth. The devotion to this
developmental step transition is prevailing irremediable for a used
meristem, plants develop different pathways to incorporate environmental
and endogenous stimuli to assure flowering at right time. There are so
many factors like hormones, sugars, temperature and photoperiod which
are responsible for flowering time regulation (Branchat et al., 2014;
Song et al., 2015; Srikanth and Schmid, 2011). In many species flowering
time has been regulated by photoperiod. Depending on the requirements of
light, plant have been divided into categories like short day, long day
and day neutral.
In day-length sensitive plants, inducing light period is mainly sense in
leaves where it causes the formation of florigen which is a long
distance signal that moves to the shoot apical meristem and results into
flowering (An et al., 2004; Corbesier et al., 2007; Mathieu et al.,
2007). The molecular complexion of florigen clarifies evidence for the
better part of the century. Nowadays FLOWERING LOCUS T(FT ) and its related genes have been identified as evolutionary
conserved campaigner, which are encoded as
phosphatidylethanolamine-binding proteins (PEBP) (Corbesier et al.,
2007; Mathieu et al., 2007). A lots of studies have nowadays
substantiated that the evolution of FLOWERING LOCUS T(FT )-like proteins play a crucial function in plant portfolio and
adaptianisms. A mobile protein; FT transmission from leaf to
shoot apex promotes flowering (Chen et al., 2018). Addition to their
crucial roles in flowering time, FT proteins serve as sovereign proteins
that intervening multiple developmental proceeding like, growth, plant
structural control, fruit and tuber formation. Under inductive
photoperiod, FT protein transports into the phloem sieve elements
and translocate to shoot apical meristem which is a good evidence thatFT is expressed in leaf phloem companion cells (PCC) (Chen et
al., 2018). At shoot apical meristem, FT interacts with FDand 14-3-3 proteins making flowering-activation complex (FAC),
which controls the exact expression of flowering time and flowering
homeotic genes to raise the transition of the vegetative part into a
reproductive inflorescence meristem ( Taoka et al., 2011; Wigge et al.,
2005; Abe et al., 2005).
In the blooming of plants, the FT protein considers as a
flowering mobile signal in the shape of a key component of florigen
(Nakamura et al., 2019). In all angiosperms examined to date,FT -like genes are responsible in regulating the floral
transition. The study of molecular evolution shows that the occurrence
of FT -like genes coexist with the progression of the flowering
spices. Therefore the part of FT in flower advancement is
well-preserved but look like to be limited to the angiosperms (P. A. Pin
and O. Nilsson 2012). These polygonal roles of FT -like proteins
have produced from extensive gene duplication actions, which happened
independently in all modern angiosperm lineages, followed by sub- or neo
functionalization. Recently, several experimental studies have been
conducted on the documentation of the mobile signal acting downstream of
leaf stimulation and activating flowering at the SAM. Based on molecular
and genetic proof, a product of the FLOWERING LOCUS T (FT )
gene, mainly the mRNA has been concerned as this signal and these
advances are reviewed in this study.