Flowering gene expression in Indonesian long harvest black rice (Oryza sativa L. ‘Cempo Ireng’)

Abstract

Many studies have reported the great potency of black rice as functional food for human diet. Cempo Ireng is one of Indonesian black rice cultivars with the highest content of anthocyanin. However, it also suffers from long harvest period. This experiment aims at investigating the behavior of the flowering genes in order to gain basic information to develop this cultivar. We sampled the leaves’ blades of Black Rice ‘Cempo Ireng’ at 48, 55, 68, 81, and 90 DAP then performed RNA isolation and cDNA synthesis, amplification of targeted flowering genes, and a semi-quantitative analysis to see the expression of flowering genes. Our results showed that the flowering genes Hd3a and RFT1 were redundantly up-regulated to induce flowering in black rice Cempo Ireng under a neutral day condition in a tropical region. We also noted that the patterns of FT-like genes and flowering regulatory genes including FT-L5, FT-L6, FT-L9, FT-L10 and Hd1, OsCOL4 were expressed together with two major flowering genes. FT-like genes were temporally co-expressed with two flowering genes Hd3a and RFT1, whereas the Hd1 had a unique expression pattern. Meanwhile, OsCOL4 as the flowering repressor was only detected in the early stage when the flowering gene Hd3a began to express. The results suggest that black rice Cempo Ireng has similar and conserved flowering pathway under a neutral day condition as indicated in the common rice flowering models.