title: Down-regulation of lipoxygenase gene reduces degradation of carotenoids of golden rice during storage.
abstract: Down-regulation of lipoxygenase enzyme activity reduces degradation of carotenoids of bio-fortified rice seeds which would be an effective tool to reduce huge post-harvest and economic losses of bio-fortified rice seeds during storage. Bio-fortified provitamin A-enriched rice line (golden rice) expressing higher amounts of β-carotene in the rice endosperm provides vitamin A for human health. However, it is already reported that degradation of carotenoids during storage is a major problem. The gene responsible for degradation of carotenoids during storage has remained largely unexplored till now. In our previous study, it has been shown that r9-LOX1 gene is responsible for rice seed quality deterioration. In the present study, we attempted to investigate if r9-LOX1 gene has any role in degradation of carotenoids in rice seeds during storage. To establish our hypothesis, the endogenous lipoxygenase (LOX) activity of high-carotenoid golden indica rice seed was silenced by RNAi technology using aleurone layer and embryo-specific Oleosin-18 promoter. To check the storage stability, LOX enzyme down-regulated high-carotenoid T3 transgenic rice seeds were subjected to artificial aging treatment. The results obtained from biochemical assays (MDA, ROS) also indicated that after artificial aging, the deterioration of LOX-RNAi lines was considerably lower compared to β-carotene-enriched transgenic rice which had higher LOX activity in comparison to LOX-RNAi lines. Furthermore, it was also observed by HPLC analysis that down-regulation of LOX gene activity decreases co-oxidation of β-carotene in LOX-RNAi golden rice seeds as compared to the β-carotene-enriched transgenic rice, after artificial aging treatment. Therefore, our study substantially establishes and verifies that LOX is a key enzyme for catalyzing co-oxidation of β-carotene and has a significant role in deterioration of β-carotene levels in the carotenoid-enriched golden rice.
authors.affiliation: Laboratory of Translational Research on Transgenic Crops, Department of Botany, University of Calcutta, 35 Ballygunge Circular Road, Kolkata, 700019, West Bengal, India.
authors.forename: Dipak
authors.initials: D
authors.lastname: Gayen
authors.forename: Nusrat
authors.initials: N
authors.lastname: Ali
authors.forename: Sailendra Nath
authors.initials: SN
authors.lastname: Sarkar
authors.forename: Swapan K
authors.initials: SK
authors.lastname: Datta
authors.forename: Karabi
authors.initials: K
authors.lastname: Datta
mesh_terms: D015139:Blotting, Southern; D002338:Carotenoids / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D015536:Down-Regulation / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005822:Genetic Vectors / Q000378:metabolism; D008084:Lipoxygenase / Q000235:genetics* / Q000378:metabolism; D012275:Oryza / Q000201:enzymology* / Q000235:genetics*; D010641:Phenotype; D030821:Plants, Genetically Modified; D011309:Preservation, Biological; D034622:RNA Interference; D012639:Seeds / Q000235:genetics; D014170:Transformation, Genetic
chemical_list: D002338:Carotenoids; D008084:Lipoxygenase