Abstract
BackgroundPast research has shown that virus-induced phytoene desaturase (PDS) gene silencing via agroinjection in the attached and detached fruit of tomato plants results in a pale-yellow fruit phenotype. Although the PDS gene is often used as a marker for gene silencing in tomatoes, little is known about the role of PDS in fruit ripening. In this study, we investigated whether the pepper PDS gene silenced endogenous PDS genes in the fruit of two tomato cultivars, Dotaerang Plus and Legend Summer.ResultsWe found that the pepper PDS gene successfully silenced endogenous PDS in tomato fruit at a silencing frequency of 100% for both cultivars. A pale-yellow silenced area was observed over virtually the entire surface of individual fruit due to the transcriptional reduction in phytoene desaturase (PDS), zeta-carotene (ZDS), prolycopene isomerase (CrtlSO), and beta-carotene hydroxylase (CrtR-b2), which are the carotenoid biosynthesis genes responsible for the red coloration in tomatoes. PDS silencing also affected the expression levels of the fruit-ripening genes Tomato AGAMOUS-LIKE1 (TAGL1), RIPENING INHIBITOR (RIN), pectin esterase gene (PE), lipoxygenase (LOX), FRUITFULL1/FRUITFUL2 (FUL1/FUL2), and the ethylene biosynthesis and response genes 1-aminocyclopropane-1-carboxylate oxidase 1 and 3 (ACO1 and ACO3) and ethylene-responsive genes (E4 and E8).ConclusionThese results suggest that PDS is a positive regulator of ripening in tomato fruit, which must be considered when using it as a marker for virus-induced gene silencing (VIGS) experiments in order to avoid fruit-ripening side effects.
Highlights
Past research has shown that virus-induced phytoene desaturase (PDS) gene silencing via agroinjection in the attached and detached fruit of tomato plants results in a pale-yellow fruit phenotype
Tomatoes injected with the buffer solution or tobacco rattle virus 1 (TRV1)/2, which were used as controls, did not exhibit any silencing symptoms and developed the customary red color, those tomatoes injected with the buffer solution were a deeper red compared to those injected with TRV1/2 for both cultivars (Fig. 2A, B)
We investigated whether PDS silencing affected carotenoid accumulation in tomatoes by measuring the expression levels of the carotenoid biosynthesis genes (ZDS, beta-carotene hydroxylase (CrtR-b2), and CrtlSO), which are involved in carotenoid biosynthesis, using qRTPCR (Fig. 3A–F)
Summary
Past research has shown that virus-induced phytoene desaturase (PDS) gene silencing via agroinjection in the attached and detached fruit of tomato plants results in a pale-yellow fruit phenotype. The PDS gene is often used as a marker for gene silencing in tomatoes, little is known about the role of PDS in fruit ripening. Application of VIGS was first achieved with the silencing of the phytoene desaturase (PDS) gene in tobacco leaves, resulting in visible leaf photo-bleaching [1]. With the aim of optimizing the VIGS approach, PDS is widely used as a common marker gene in many plant species due to its ease of detection. The use of VIGS in tomatoes was first achieved by silencing PDS in leaves [6], followed by many more successful PDS-silencing experiments on tomato fruit [7,8,9]. The increase in carotenoid content (in the order of a 10- to 14-fold increase) during the ripening of tomatoes has been reported [10].
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