The Phytoene synthase gene family of apple (Malus x domestica) and its role in controlling fruit carotenoid content

Abstract

BackgroundCarotenoid compounds play essential roles in plants such as protecting the photosynthetic apparatus and in hormone signalling. Coloured carotenoids provide yellow, orange and red colour to plant tissues, as well as offering nutritional benefit to humans and animals. The enzyme phytoene synthase (PSY) catalyses the first committed step of the carotenoid biosynthetic pathway and has been associated with control of pathway flux. We characterised four PSY genes found in the apple genome to further understand their involvement in fruit carotenoid accumulation.ResultsThe apple PSY gene family, containing six members, was predicted to have three functional members, PSY1, PSY2, and PSY4, based on translation of the predicted gene sequences and/or corresponding cDNAs. However, only PSY1 and PSY2 showed activity in a complementation assay. Protein localisation experiments revealed differential localization of the PSY proteins in chloroplasts; PSY1 and PSY2 localized to the thylakoid membranes, while PSY4 localized to plastoglobuli. Transcript levels in ‘Granny Smith’ and ‘Royal Gala’ apple cultivars showed PSY2 was most highly expressed in fruit and other vegetative tissues. We tested the transient activation of the apple PSY1 and PSY2 promoters and identified potential and differential regulation by AP2/ERF transcription factors, which suggested that the PSY genes are controlled by different transcriptional mechanisms.ConclusionThe first committed carotenoid pathway step in apple is controlled by MdPSY1 and MdPSY2, while MdPSY4 play little or no role in this respect. This has implications for apple breeding programmes where carotenoid enhancement is a target and would allow co-segregation with phenotypes to be tested during the development of new cultivars.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0573-7) contains supplementary material, which is available to authorized users.

Genetics of Pigment Biosynthesis and Degradation

“…Most are likely to act indirectly in promoting carotenoid biosynthesis, perhaps by activating ethylene biosynthesis, although some (e.g. the MADS-box gene RIN and the NAC TF SlNAC1) have been shown to bind the carotenoid biosynthetic gene promoters directly (Ampomah-Dwamena et al 2015;Ma et al 2014). There is also growing evidence of the importance of non-transcriptional regulation of carotenoid production.…”

A kiwifruit (Actinidia deliciosa) R2R3‐MYB transcription factor modulates chlorophyll and carotenoid accumulation

“…High-performance liquid chromatography (HPLC) analysis was performed on a Dionex Ultimate 3000 solvent delivery system (Thermo Scientific, Waltham, MA, USA) fitted with a YMC RP C30 column (5 lm, 250 9 4.6 mm), coupled to a 20 9 4.6 C30 guard column (YMC Inc., NC, USA) and a Dionex 3000 PDA detector as previously reported (Ampomah-Dwamena et al, 2015). Phytoene was monitored at 280 nm and coloured carotenoids and Chlb were detected at 450 nm, while Chla and its derivatives were monitored at 400 nm.…”

“…In Arabidopsis, a single PSY is present and therefore the regulation of transcript abundance is essential to this step (Rodriguez-Villalon et al, 2009;Cazzonelli & Pogson, 2010). In other species such as maize, rice, apple and loquat, some redundancy is provided by multiple PSY genes (Li et al, 2008;Welsch et al, 2008;Fu et al, 2014;Ampomah-Dwamena et al, 2015). The tissue-specific expression observed between different PSYs in these species suggests a tightly regulated transcription of this step.…”

Regulation of Banana Phytoene Synthase (MaPSY) Expression, Characterization and Their Modulation under Various Abiotic Stress Conditions

“…Many plant species are known to have multiple copies of PSY gene (Gallagher et al, 2004; Clotault et al, 2008; Giorio et al, 2008; Li et al, 2008; Fu et al, 2014; Ampomah-Dwamena et al, 2015). The presence of multiple PSY in plants is a result of gene duplication events, which have significance for function and modulation of carotenogenesis (Gallagher et al, 2004; Ampomah-Dwamena et al, 2015).…”

“…Many plant species are known to have multiple copies of PSY gene (Gallagher et al, 2004; Clotault et al, 2008; Giorio et al, 2008; Li et al, 2008; Fu et al, 2014; Ampomah-Dwamena et al, 2015). The presence of multiple PSY in plants is a result of gene duplication events, which have significance for function and modulation of carotenogenesis (Gallagher et al, 2004; Ampomah-Dwamena et al, 2015). A number of PSY genes have been overexpressed in various plants, such as rice (Ye et al, 2000), tobacco (Busch et al, 2002), tomato (Fraser et al, 2002) and arabidopsis (Maass et al, 2009) leading to enhanced biosynthesis of carotenoids in a specific tissue.…”