Decoding the regulatory control of floral induction in apple (Malus domestica)

Floral induction (FI), the decision enabling a meristem to become floral, is important to reproductive success and yield production, yet its transcriptional regulation is virtually unknown in apple and other fruit tree species.

The central FI mechanism appears conserved in all species in which it has been studied, although it is the regulation that enables environmental adaptation.

FI is activated via multiple environmental and internal cues, mediated through various flowering pathways and converging at the highly homologous genes, FLOWERING LOCUS T (FT) and TERMINAL FLOWER 1 (TFL1), which act as an FI promoter and inhibitor, respectively.

In Arabidopsis, flowering pathways have been extensively studied; however, the perennial lifecycle, dormancy requirements and flowering behaviour of apple, in addition to the ancestral duplication of the genome, mean FI control is likely very different in this species.

The transcription factors (TF) and cis binding motifs identified in Arabidopsis provide a starting point from which to unravel apple FI regulation and it appears the GA pathway may also play an important role.

FlowCODE will decipher the molecular control of FI in apple by identifying TFs that control transcription of FT- and TFL1-like genes and how they affect this expression. Equally, regulatory elements within the apple FT and TFL1 genes will also be ascertained.

The significant genetic variation in FI-related traits, such as the proportion of floral buds per tree, across apple varieties will be used as a tool to link molecular regulation with its phenotypic effects.

Additionally, studying this regulation in the context of the GA pathway will provide insight into its role in influencing this variation in FI behaviour.

In deciphering FI regulation, possible approaches to protect fruit production from climate challenges will be revealed and enable development of more resilient varieties of apple and other fruit tree species through new breeding technologies.