Molecular screening reveals a photoperiod responsive floral regulator in sugarcane

Abstract

Flowering is a major factor that can decrease sugarcane productivity because it affects the quantity and quality of feedstock due to sucrose consumption from the stalk during inflorescence formation. Photoperiod is the main environmental factor involved in sugarcane floral induction, which occurs by the integration of gene regulatory networks in response to environmental and endogenous stimuli. One of the gene families involved in these regulatory networks are orthologs of the Arabidopsis thaliana FLOWERING LOCUS T (FT) gene, which encodes a phloem-mobile signal that stimulates floral induction at the shoot apical meristem. This work investigates homologs of the FT gene in sugarcane, as well as determines the putative function of these genes under inductive short-day photoperiods. We conducted in silico analyses to isolate putative FT orthologs in sugarcane and examined the expression levels of these genes under different photoperiodic conditions over a 24-hour-day-cycle in contrasting cultivars with different flowering responses. Three new FT orthologs were found with high similarity to FT homologs in other species. Among three genes identified, we focused on ScFT6, which has conserved amino acid sequence domains at characteristic positions for the flowering inducer of the phosphatidylethanolamine-binding protein (PEBP) gene family. ScFT6 expression varied according to diurnal variation and demonstrated a high transcriptional level under inductive shortening-day conditions. Cultivars with distinct flowering time responses display variable expression for the ScFT6. Therefore, ScFT6 is a putative orthologous gene in relation to FT that is controlled by photoperiod and diurnal regulation in sugarcane.