Ruie Liu, Alexandre How-Kit, Linda Stammitti, Emeline Teyssier, Dominique Rolin, Anne Mortain-Bertrand, Stefanie Halle, Mingchun Liu, Junhua Kong, Chaoqun Wu, Charlotte Degraeve-Guibault, Natalie H. Chapman, Mickael Maucourt, T. Charlie Hodgman, Jörg Tost, Mondher Bouzayen, Yiguo Hong, Graham B. Seymour, James J. Giovannoni, and Philippe Gallusci

Significance

This work shows that active DNA demethylation governs ripening, an important plant developmental process. Our work defines a molecular mechanism, which has until now been missing, to explain the correlation between genomic DNA demethylation and fruit ripening. It demonstrates a direct cause-and-effect relationship between active DNA demethylation and induction of gene expression in fruits. The importance of these findings goes far beyond understanding the developmental biology of ripening and provides an innovative strategy for its fine control through fine modulation of epimarks in the promoters of ripening related genes. Our results have significant application for plant breeding especially in species with limited available genetic variation.

Abstract

In plants, genomic DNA methylation which contributes to development and stress responses can be actively removed by DEMETER-like DNA demethylases (DMLs). Indeed, in Arabidopsis DMLs are important for maternal imprinting and endosperm demethylation, but only a few studies demonstrate the developmental roles of active DNA demethylation conclusively in this plant. Here, we show a direct cause and effect relationship between active DNA demethylation mainly mediated by the tomato DML, SlDML2, and fruit ripening— an important developmental process unique to plants. RNAi SlDML2 knockdown results in ripening inhibition via hypermethylation and repression of the expression of genes encoding ripening transcription factors and rate-limiting enzymes of key biochemical processes such as carotenoid synthesis. Our data demonstrate that active DNA demethylation is central to the control of ripening in tomato.

See: http://www.pnas.org/content/112/34/10804.abstract.html?etoc

PNAS August 25, 2015;   vol. 112 no. 34:10804–10809

Fig. 2.

Phenotypes of tomato DML RNAi fruits. (A) Fruits (70 dpa) (upper lane) or fruit sections (lower lane) from eight independent representative T0 RNAi plants. (B) Fruits (85 dpa) from T2 plants (left to right); WT plants, line 2 plants (DML2A and DML2B), line 8 plants (DML8A and DML8B), and an azygous plant (AZ). (C) Ripening kinetics of WT (Top), DML8A (Middle), and DML2A (Bottom). (D) WT bicarpel (Upper) DML2B multicarpel fruits (Lower). (E) VIGS experiment on 47-dpa (Br + 5) fruits injected with PVX/SlDML2 [fruits (1) and (3)] or PVX [fruits (2) and (4)] at 12 dpa [fruits (3) and (4)] inside of fruits (1) and (2), respectively. (Scale bars: 1 cm.)