Molecular Genetic Dissection of Sugarcane Flowering under Equatorial Field Conditions

Abstract

Sugarcane is a tropical crop used for sugar and biofuel production in tropical and equatorial regions of the globe. Sugarcane flowering is intrinsically induced in equatorial regions due to long-day conditions. Flower development is problematic for this crop because it halts vegetative growth, leading to a reduction of the sugar accumulated in the stalks, and significant yield loss. Notwithstanding, the identification of genes differentially expressed in contrasting cultivars can potentially reveal markers and tools to generate genotypes more suitable for expanding the geographical limits of this crop. Thus, dissecting the flowering gene expression network under field conditions is highly relevant for breeding. We report the analysis of subtractive cDNA libraries produced from shoot apical meristem of cultivars contrasting for flowering time growing in production fields under equatorial conditions. Transcripts with homology to POLYPHENOL OXIDASE (PPO), CALMODULIN (CAM), PHOSPHATIDYLCHOLINE/PHOSPHATIDYLINOSITOL-TRANSFER PROTEIN (SEC14), OBTUSIFOLIOL-14-Α-DEMETHYLASE (CYP51), 14–3-3, and the phosphotransferases SHAGGY KINASE (GSK), PROTEIN KINASE C INHIBITOR (PKCI), and SERINE/THREONINE PHOSPHATASE (PP1) were identified as differentially expressed in the subtractive libraries and further chosen for RT-qPCR validation and in silico interactome analyses. Our results suggest that ScPPO, ScSEC14 and Sc14–3-3 may act as flowering inhibitors. RT-qPCR data also revealed two 14–3-3 isoforms as potential flowering markers. Sc14–3-3 was structurally and phylogenetically characterized and its genomic architecture was analysed in two BAC clones, showing that they probably correspond to two different loci with confirmed synteny to other grass genomes. This work reveals potential novel mechanisms of flowering in grasses with implications to crop breeding.