A Complex Gene Network Mediated by Ethylene Signal Transduction TFs Defines the Flower Induction and Differentiation in Olea europaea L.

Amelia Salimonti,Francesco Sunseri,Fabrizio Carbone,Francesco Mercati,Ivano Forgione,Guglielmo Puccio,Antonio Mauceri,Tiziana Maria Sirangelo

doi:10.3390/genes12040545

Abstract

The olive tree (Olea europaea L.) is a typical Mediterranean crop, important for olive and oil production. The high tendency to bear fruits in an uneven manner, defined as irregular or alternate bearing, results in a significant economic impact for the high losses in olives and oil production. Buds from heavy loaded (‘ON’) and unloaded (‘OFF’) branches of a unique olive tree were collected in July and the next March to compare the transcriptomic profiles and get deep insight into the molecular mechanisms regulating floral induction and differentiation. A wide set of DEGs related to ethylene TFs and to hormonal, sugar, and phenylpropanoid pathways was identified in buds collected from ‘OFF’ branches. These genes could directly and indirectly modulate different pathways, suggesting their key role during the lateral bud transition to flowering stage. Interestingly, several genes related to the flowering process appeared as over-expressed in buds from March ‘OFF’ branches and they could address the buds towards flower differentiation. By this approach, interesting candidate genes related to the switch from vegetative to reproductive stages were detected and analyzed. The functional analysis of these genes will provide tools for developing breeding programs to obtain olive trees characterized by more constant productivity over the years.

Highlights

The olive tree (O. europaea L.), which belongs to Oleaceae, is an evergreen plant native and is largely cultivated in the Mediterranean Basin
The later buds were collected at two stages alongside flower development, in July and the following March, when the flower induction as well as lateral buds break and the flowering occur, respectively
Our study provided new insights into olive flower biology in the framework of the alternate bearing, with a particular focus on the molecular mechanisms underlying both flower induction, differentiation, and their relationship

Summary

Introduction

The olive tree (O. europaea L.), which belongs to Oleaceae, is an evergreen plant native and is largely cultivated in the Mediterranean Basin. The cultivated forms have been introduced into many areas worldwide [1] as they are one of the most economically important fruit crops and there are many nutritional and health benefits of olive fruits and the derived oil. In addition to these agricultural and dietary qualities, the olive tree frequently exhibits a high tendency to bear fruits in an uneven manner, resulting in a significant economic impact, as oil olives are an industry-dependent commodity [2,3,4]. Alternate bearing determines harvest yield variation in olive tree depending on genetic and physiological factors, as well as environment influence

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