Panicle development

The rice inflorescence, called panicle, is characterized by a complex branching pattern controlled by numerous regulatory genes. Rice florigens also play a crucial role in activating the expression of the FLOWERING LOCUS T LIKE 1 (FTL1) gene, which encodes a protein similar to Hd3a and RFT1. Unlike these, however, FTL1 is transcribed and translated directly in the shoot apical meristem. This mechanism suggests the existence of a unique three-florigen system in cereals, whose interaction regulates the final size of the panicle.

Analysis of OsFTL1 during rice panicle development: localization of FTL1 mRNA (right) and protein (left) during different stages of inflorescence and flower development. Abbreviations are as follows: VM – vegetative meristem; IM – inflorescence meristem; PBM – primary branch meristem; SBM – secondary branch meristem; SM/FM – spikelet meristem and floral meristem (adapted from Giaume et al. 2023).

Panicle phenotype of rice lines with mutations in the FTL1 gene: rice panicles carrying mutations in FTL1 are more highly branched, showing a significant increase in secondary and tertiary branches, especially when plants are grown under open field conditions (adapted from Giaume et al. 2023).