Genomic and Biotechnology of the Fruit GBF

Ethylen signaling, stress tolerence and fruit maturation

Farid Regad, Julien PIRRELLO, Anne Bernadac, Mondher Bouzayen

Ethylene is a gaseous phytohormone involved in many plant developmental processes such as developmental process, but also in biotic or abiotic stress (Fig.1). Ripening of climacteric fruit as tomato is mainly control by ethylene. On this process ethylene is firstly involved in the modification of colour, synthesis of aroma, softening of fruit and is responsible of the over-ripening of fruit and the degradation of organoleptic quality of fruit.

Figure 1: Ethylene is involved biotic or abiotic stress but also in developmental process

The control of the ethylene response constitutes an important economical and agronomical challenge. Ethylene transduction pathway have been described, linear and invariant whatever the developmental stage or environmental condition. Ethylene Response Factors (ERF) are the last known actors of the ethylene transduction pathway. They have been shown to be involved in processes as diverse as biotic and abiotic stresses as well as in seed germination. They are good candidate to explain the diversity of response to ethylene.

Figure 2: ERFs are the last actors of ethylene transduction pathway. ERFs diversity (more than 60 on Arabidopsis plant model) may explain the diversity of response to ethylene.

We are isolating tomato ERFs to determine the involvement of each one on the different part of the ethylene response. To better understand the function of each one we study their expression pattern in different tissues and their activity (activator or repressor) on different promoter. However, since ERF is a huge family with diverse functions it is wise to consider the flanking region of the AP2/ERF domain which is highly conserved to gain more insight on the functionality of the ERFs. Indeed, there is an important variability outline the DNA binding domain, suggesting a wide range of function for ERF family.

It is known that ERFs can bind the GCC box cis-element present in the promoter of many biotic stress related genes. This cis-element is sufficient to confer ethylene response to a promoter.

The control of ERFs regulation and of their target gene is a biotechnological challenge. Indeed, these new insights will give opportunity to improve fruit quality and allow an integrated production thanks to a better resistance to stress.