Abstract
Carotenoids are isoprenoid pigments synthesized in plants, algae, and photosynthetic bacteria and fungus. Their role is essential in light capture, photoprotection, pollinator attraction, and phytohormone production. Furthermore, they can regulate plant development when they are processed as small signaling molecules. Due to their importance for human health, as promoters of the immune system and antioxidant activity, carotenoids have been used in the pharmaceutical, food, and nutraceutical industries. Regulation of carotenoid synthesis and accumulation has been extensively studied. Excellent work has been done unraveling the mode of action of phytoene synthase (PSY), a rate-limiting enzyme of carotenoid biosynthesis pathway, in model species and staple crops. Lately, interest has been turned to Orange protein and its interaction with PSY during carotenoid biosynthesis. Discovered as a dominant mutation in Brassica oleracea, Orange protein regulates carotenoid accumulation by posttranscriptionally regulating PSY, promoting the formation of carotenoid-sequestering structures, and also preventing carotenoid degradation. Furthermore, Orange protein contributes to homeostasis regulation, improving plant tolerance to abiotic stress. In this mini review, the focus is made on recent evidence that elucidates Orange protein mode of action and expression in different plant species. Additionally, strategies are proposed to modify Orange gene by utilization of genome editing techniques. A better understanding of carotenoid biosynthesis and accumulation will lead to a positive impact on the development of healthy food for a growing population.
Highlights
PRESENCE OF ORANGE GENE IN HIGHER PLANTSRecognized as a dominant spontaneous mutation in Brassica oleracea, which confers orange color to the influorescence, Orange gene has proven to play an important role in carotenoid accumulation by activating chromoplast differentiation in nongreen tissues (Lu et al, 2006)
Carotenoids are isoprenoid pigments synthesized in plants, algae, and photosynthetic bacteria and fungus
The focus is made on the role of Orange protein as a regulator of carotenoid accumulation in different plant species and its interaction with phytoene synthase, which has been named a key enzyme in the carotenoid pathway, with special emphasis on efforts to manipulate the Orange gene to stimulate carotenoid accumulation
Summary
Recognized as a dominant spontaneous mutation in Brassica oleracea, which confers orange color to the influorescence, Orange gene has proven to play an important role in carotenoid accumulation by activating chromoplast differentiation in nongreen tissues (Lu et al, 2006). Orange gene (OR) encodes for a protein belonging to the DnaJ cysteine-rich zinc finger protein domain, which is a highly conserved sequence among diverse plant species (Lu et al, 2006; Tzuri et al, 2015; Pulido and Leister, 2018), had positioned Orange protein in the nucleus (Zhou et al, 2011; Kim et al, 2013; Sun et al, 2016), suggesting that interaction with nuclear elements such as transcription factors is required to initiate plastid transition and carotenoid accumulation (Sun et al, 2016). Analysis of the interaction of BoOr and cauliflower eukaryotic release factor 1 protein (eRF1) revealed an antagonist effect, with an increase in the length of the petiole because of suppression of BoeRF1 family genes when BoOr was expressed (Zhou et al, 2011)
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