The Significance of Florigen Activation Complex in Controlling Flowering in Rice

Yield potential, plant height and flowering time are three classes of traits that determine the productivity of rice. Rice heading greatly depends on the accurate measurement of environment changes, particularly in day length and temperature. We discuss all genes reported to be related to the heading time in this review. The accumulation of florigen, such as Hd3a or RFT1, is the key factor for rice heading. Florigen is found in the rice leaf and then transports into the shoot apical meristem (SAM), where floral initiation occurs. We discuss the formation of florigen activation complex (FAC) with 14-3-3 and FD1 proteins to induce the expression of flowering genes. In addition, two key pathways related to heading date, GI-Hd1-Hd3a and Ghd7-Ehd1-Hd3a/RFT1 are introduced in this review. We summarize proteins with histone modification functions, due to the modification of histone is also significant for heading date. The flowering time also extremely dependent on the environments, including nutrient availability, abiotic and biotic stresses, we argue the phenotypes of rice heading date under different extreme environments, as well. Lastly, we gather genes that are reported having a change in heading time, but their detail molecular regulation is still elusive. Thus, this review introduces heading time systematically, providing knowledge and ideas for researchers to study further the phenotype of heading time.