Discussion
Flowering by C. pallens , when growing in natural conditions, is
highly variable. Consequently, it is difficult to track the induction of
the flowering process using only unmanipulated plants. Transplanting
plants to a lower altitude (15 m, University of Canterbury) and warmer
temperature conditions induced heavy flowering in C. pallens , as
previously reported for C. rigida (Mark, 1965), allowing sample
collection during the inductive summer period and enabling us to study
the molecular regulators of flowering. With recent advances in
sequencing technologies, transcriptomic profiling of non-model plant
species has been demonstrated to be advantageous and effective when
studying ecological phenomena (Miyazaki et al., 2014; Todd et al.,
2016). In the present study, the use of ecological transcriptomics
enabled the identification of key orthologous flowering-time gene(s) inC. pallens responsible for regulating the floral transition.
Transcriptomic profiling of multiple? orthologous floral protein
sequences showed that many components of the flowering pathways
identified in Arabidopsis and B. distachyon were also conserved
in C. pallens . For example, VRN genes, which are known to
regulate the floral transition in response to vernalisation and
temperature in temperate grasses (Ream et al., 2014), were also
identified successfully using the global transcriptomic approach.
Phylogenetic characterisation followed by expression profiling of thePEBP -genes resulted in characterisation of the floral promoting
genes. Similar to other species, including Arabidopsis, rice, maize,
barley, wheat and B. distachyon (Karlgren et al., 2011; Liu et.
al., 2016), the identified PEBP-like sequences from C.
pallens could be categorised into their potential subfamilies. Five of
the sequences were shown to be FT-like sequences. Most of the sequences
grouped with sequences which have already been functionally
characterised, which aided in predicting function. All of theCpFT-like genes showed similar seasonal expression patterns
(except for CpFT1 ), with their greatest expression during the
spring season. This pattern of expression is similar to the expression
of FTs characterised in other plant species (Nagano et al., 2019)
but none of them could be correlated with the induction of the floral
transition in the tillers that flowered in the next season. This could
be because the activation of the floral transition in C. pallensoccurs during summer rather than in spring when the expression of theFT-like genes was at its peak.