Abstract
Vitamin A deficiency (VAD) is the leading cause of blindness among children and is associated with high risk of maternal mortality. In order to enhance the bioavailability of vitamin A, high carotenoid transgenic golden rice has been developed by manipulating enzymes, such as phytoene synthase (psy) and phytoene desaturase (crtI). In this study, proteome and metabolite analyses were carried out to comprehend metabolic regulation and adaptation of transgenic golden rice after the manipulation of endosperm specific carotenoid pathways. The main alteration was observed in carbohydrate metabolism pathways of the transgenic seeds. The 2D based proteomic studies demonstrated that carbohydrate metabolism-related enzymes, such as pullulanase, UDP-glucose pyrophosphorylase, and glucose-1-phosphate adenylyltransferase, were primarily up-regulated in transgenic rice seeds. In addition, the enzyme PPDK was also elevated in transgenic seeds thus enhancing pyruvate biosynthesis, which is the precursor in the carotenoids biosynthetic pathway. GC-MS based metabolite profiling demonstrated an increase in the levels of glyceric acid, fructo-furanose, and galactose, while decrease in galactonic acid and gentiobiose in the transgenic rice compared to WT. It is noteworthy to mention that the carotenoid content, especially β-carotene level in transgenic rice (4.3 μg/g) was significantly enhanced. The present study highlights the metabolic adaptation process of a transgenic golden rice line (homozygous T4 progeny of SKBR-244) after enhancing carotenoid biosynthesis. The presented information would be helpful in the development of crops enriched in carotenoids by expressing metabolic flux of pyruvate biosynthesis.
Highlights
Carotenoids have a high nutritional value and play a pivotal role in physiological functions such as vision, growth, reproduction, cellular differentiation, proliferation, and immunity (Tang et al, 2009; Wurtzel et al, 2012)
The carotenoid pathway in rice was genetically modified by the introduction of exogenous psy and crtI along with an endospermspecific glutelin promoter (Datta et al, 2006)
The proteome profiles and metabolites of transgenic golden rice line (T4 progeny of SKBR-244) with high carotenoid content were compared with its non-transgenic counterpart BR29 rice
Summary
Carotenoids have a high nutritional value and play a pivotal role in physiological functions such as vision, growth, reproduction, cellular differentiation, proliferation, and immunity (Tang et al, 2009; Wurtzel et al, 2012). Modern advancements in the field of biotechnology have enabled the development of genetically modified (GM) crops overexpressing provitamin A. Such crops include rice (Datta et al, 2003, 2014; Paine et al, 2005; Parkhi et al, 2005; Schaub et al, 2005; Gayen et al, 2015), potato (Römer et al, 2002), tomato (Fraser et al, 2009), canola (Shewmaker et al, 1999) and maize (Zhu et al, 2008). Insertion of transgene into the rice genome may lead to unintended changes which alters endogenous gene expression, subsequently leading to changes in macro- or micro-nutrients, anti-nutritional factors or other essential nutritional component of rice seed
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