Abstract
Histone deacetylation is one of the well characterized post-translational modifications related to transcriptional repression in eukaryotes. The process of histone deacetylation is achieved by histone deacetylases (HDACs). Over the last decade, substantial advances in our understanding of the mechanism of fruit ripening have been achieved, but the role of HDACs in this process has not been elucidated. In our study, an RNA interference (RNAi) expression vector targeting SlHDA1 was constructed and transformed into tomato plants. Shorter fruit ripening time and decreased storability were observed in SlHDA1 RNAi lines. The accumulation of carotenoid was increased through an alteration of the carotenoid pathway flux. Ethylene content, ethylene biosynthesis genes (ACS2, ACS4 and ACO1, ACO3) and ripening-associated genes (RIN, E4, E8, Cnr, TAGL1, PG, Pti4 and LOXB) were significantly up-regulated in SlHDA1 RNAi lines. In addition, the expression of fruit cell wall metabolism genes (HEX, MAN, TBG4, XTH5 and XYL) was enhanced compared with wild type. Furthermore, SlHDA1 RNAi seedlings displayed shorter hypocotyls and were more sensitive to ACC (1-aminocyclopropane-1-carboxylate) than the wild type. The results of our study indicate that SlHDA1 functions as a negative regulator of fruit ripening by affecting ethylene synthesis and carotenoid accumulation.
Highlights
Fruit ripening is a complex regulated process that involves numerous metabolic changes, such as changes in color, flavor, aroma and nutrition
Real-time quantitative PCR results showed that the relative expression of SlHDA1 was significantly reduced in five transgenic lines compared with the wild type (Fig. 1A)
In wild type, the SlHDA1 gene was highly expressed in MG fruits compared with leaves, and a trend of a rapid increase in SlHDA1 was observed along with the fruit ripening (Fig. 1B), indicating that SlHDA1 may be related to tomato fruit ripening
Summary
Fruit ripening is a complex regulated process that involves numerous metabolic changes, such as changes in color, flavor, aroma and nutrition. In climacteric fruits (e.g. tomato, apple and banana), ethylene plays important roles in fruit development and ripening and is an essential factor for the ripening process[4, 5]. Previous studies revealed that RNAi inhibition of SlACO1 delays ripening of climacteric fruits[9, 10]. These findings indicated that normal function of ethylene biosynthesis is essential for the ripening process. E8 is another a ripening-associated, fruit-specific expression gene in tomato that is regulated by ethylene[13]. The regulatory mechanisms controlling fruit ripening in tomato have been studied extensively. There have been some reports on HDACs in Arabidopsis and rice, but rarely in tomato
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