The NAC transcription factor FaRIF controls fruit ripening in strawberry

In contrast to climacteric fruits such as tomato, the knowledge on key regulatory genes controlling the ripening of strawberry, a non-climacteric fruit, is still limited. NAC transcription factors mediate different developmental processes in plants. Here, we identified and characterized FaRIF (Ripening Inducing Factor), a NAC transcription factor that is highly expressed and induced in strawberry receptacles during ripening. Functional analyses based on stable transgenic lines aimed at silencing FaRIF by RNA interference, either from a constitutive promoter or the ripe receptacle-specific EXP2 promoter, as well as overexpression lines showed that FaRIF controls critical ripening-related processes such as fruit softening and pigment and sugar accumulation. Physiological, metabolome and transcriptome analyses of receptacles of FaRIF-silenced and overexpression lines point to FaRIF as a key regulator of strawberry fruit ripening from early developmental stages, controlling abscisic acid (ABA) biosynthesis and signaling, cell wall degradation and modification, the phenylpropanoid pathway, volatiles production, and the balance of the aerobic/anaerobic metabolism. FaRIF is therefore a target to be modified/edited to control the quality of strawberry fruits. Overall design: Transcriptome analysis from strawberry receptacles from control and 35Spro:FaRIF-RNAi #3 and 35Spro:FaRIF-RNAi #11 transgenic lines at the white and red stages or ripening, and from receptacles of control and EXP2pro:FaRIF-RNAi #1, EXP2pro:FaRIF-RNAi #7 and 35Spro:FaRIF #1 at the red stage. Three biological replicates of each sample was analyzed.