Discussion
C. pallens is a non-model monocot species with a large genome (2n = 42) (Connor, 1991). Due to highly variable flowering in C. pallens growing in natural conditions, it would have been 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 inC. 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 (Todd et al., 2016). In the present study, use of ecological transcriptomics resulted in the identification of key orthologous flowering-time gene(s) in C. pallens responsible for regulating the floral transition. Transcriptomic profiling of different orthologous floral protein sequences showed that many components of the flowering pathways identified in A. thaliana 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. Like maize, which has 26 homologous PEBP sequences (Liu et. al., 2016), C. pallens has multiple copies of PEBP gene sequences. This may be attributed to the polyploid nature of the plant, along with gene duplication events. The identified PEBP-like sequences from C. pallens were categorised into their 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 due to the fact that the activation of the floral transition inC. pallens occurs during summer rather than in spring when the expression of the FT-like genes was at its peak.