Abstract
BackgroundIn soft fruits, the differential expression of many genes during development and ripening is responsible for changing their organoleptic properties. In strawberry fruit, although some genes involved in the metabolic regulation of the ripening process have been functionally characterized, some of the most studied genes correspond to transcription factors. High throughput transcriptomics analyses performed in strawberry red receptacle (Fragaria x ananassa) allowed us to identify a ripening-related gene that codes an atypical HLH (FaPRE1) with high sequence homology with the PACLOBUTRAZOL RESISTANCE (PRE) genes. PRE genes are atypical bHLH proteins characterized by the lack of a DNA-binding domain and whose function has been linked to the regulation of cell elongation processes.ResultsFaPRE1 sequence analysis indicates that this gene belongs to the subfamily of atypical bHLHs that also includes ILI-1 from rice, SlPRE2 from tomato and AtPRE1 from Arabidopsis, which are involved in transcriptional regulatory processes as repressors, through the blockage by heterodimerization of bHLH transcription factors. FaPRE1 presented a transcriptional model characteristic of a ripening-related gene with receptacle-specific expression, being repressed by auxins and activated by abscisic acid (ABA). However, its expression was not affected by gibberellic acid (GA3). On the other hand, the transitory silencing of FaPRE1 transcription by agroinfiltration in receptacle produced the down-regulation of a group of genes related to the ripening process while inducing the transcription of genes involved in receptacle growth and development.ConclusionsIn summary, this work presents for the first time experimental data that support an important novel function for the atypical HLH FaPRE1 during the strawberry fruit ripening. We hypothesize that FaPRE1 modulates antagonistically the transcription of genes related to both receptacle growth and ripening. Thus, FaPRE1 would repress the expression of receptacle growth promoting genes in the ripened receptacle, while it would activate the expression of those genes related to the receptacle ripening process.
Highlights
In soft fruits, the differential expression of many genes during development and ripening is responsible for changing their organoleptic properties
Phylogenetic analysis showed that FaPRE1, FaPRE2 and FaPRE3 proteins can be classified into the atypical HLH subgroup 16 of the 32 plant Basic helixloop-helix (bHLH)/HLH subfamilies [22] (Additional files 1, 2)
The atypical HLHs interact with bHLHs transcription factors and, in this way, interfere with their regulatory activity by blocking its binding to the cis-regulatory sequences positioned on the gene promoters that regulate
Summary
The differential expression of many genes during development and ripening is responsible for changing their organoleptic properties. Some genes involved in the metabolic regulation of the ripening process have been functionally characterized, some of the most studied genes correspond to transcription factors. During the processes of development and ripening of soft fruits, many metabolic pathways that are responsible for organoleptic properties are differentially expressed. With the exception of some transcriptional factors (TFs), the functional characterization of genes involved in the regulation of these metabolic pathway is very scarce until now. A DOF-type TF (FaDOF2) has been identified as a positive regulator of eugenol biosynthesis in ripened strawberry receptacle Both FaEOBII and FaDOF2 seem to act synergistically in the activation of the FaEGS2 gene transcription [11]. A comparation between a mutant whited coloured strawberry and a red natural one has discovered some TF potentially involved in the anthocyanin biosynthesis [18]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
