A SEPALLATA gene is involved in the development and ripening of strawberry (Fragaria x ananassa Duch.) fruit, a non-climacteric tissue.

Climacteric and non-climacteric fruits have traditionally been viewed as representing two distinct programmes of ripening associated with differential respiration and ethylene hormone effects. In climacteric fruits, such as tomato and banana, the ripening process is marked by increased respiration and is induced and co-ordinated by ethylene, while in non-climacteric fruits, such as strawberry and grape, it is controlled by an ethylene-independent process with little change in respiration rate. The two contrasting mechanisms, however, both lead to texture, colour, and flavour changes that probably reflect some common programmes of regulatory control. It has been shown that a SEPALLATA(SEP)4-like gene is necessary for normal ripening in tomato. It has been demonstrated here that silencing a fruit-related SEP1/2-like (FaMADS9) gene in strawberry leads to the inhibition of normal development and ripening in the petal, achene, and receptacle tissues. In addition, analysis of transcriptome profiles reveals pleiotropic effects of FaMADS9 on fruit development and ripening-related gene expression. It is concluded that SEP genes play a central role in the developmental regulation of ripening in both climacteric and non-climacteric fruits. These findings provide important information to extend the molecular control of ripening in a non-climacteric fruit beyond the limited genetic and cultural options currently available.

Genetic identification and genomic organization of factors affecting fruit texture.

Fleshy fruits are an essential part of the human diet providing vital vitamins, minerals and other health-promoting compounds. The texture of the ripe fruit has a significant effect on quality and influences consumer acceptance, shelf-life, resistance, and transportability. The development of rational approaches to improve texture and shelf-life depend on understanding the biological basis of fruit ripening. Until recently, work has focused on the isolation of ripening-related genes from a variety of fleshy fruits. However, little is known about the genes that regulate this complex developmental process or whether similar regulatory genes are active in all fruiting species. A major breakthrough would be the identification of generic genes associated with texture and other aspects of ripening in fleshy fruits. In tomato, a small number of single gene mutations exist, such as ripening-inhibitor (rin), non-ripening (nor), Never-ripe (Nr), and Colourless non-ripening (Cnr) which have pleiotropic effects resulting in the reduction or almost complete abolition of ripening. These mutations probably represent lesions in regulatory genes. The cloning of the wild-type alleles of RIN and NOR is reported by Moore et al. in this issue. This review focuses on the texture characteristics of the Cnr mutant. A possible framework for the molecular regulation of fruit texture is discussed and quantitative genetic approaches to determining the generic attributes of fruit texture are explored.