title: Functional Characterization of 9-/13-LOXs in Rice and Silencing Their Expressions to Improve Grain Qualities.
abstract: Lipoxygenases (LOXs) are involved in oxidative rancidity and render rice unsuitable for human consumption. Here, RNA interference- (RNAi-) induced gene expression inhibition was used to analyze the functions of the bran/seed-specific LOXs in rice. r9-LOX1 and L-2 (9-LOX category) were the candidate genes expressing a bran/seed-specific LOX, while RCI-1 was (13-LOX category) a plastid-specific LOX. Real-time PCR showed that three LOXs were cultivar/tissue specific expression on a certain level. r9-LOX1 and L-2 were generally much higher in active bran/seed than in stabilized bran, mature seed, and regenerated plant. RCI-1 was barely expressed in seed. In transgenic lines, r9-LOX1, as well as L-2, expression was dramatically downregulated, compared to the nontransgenic controls. SPME/GC-MS analysis of r9-LOX1 RNAi transgenic lines showed 74.33% decrease in nonanal content (formed during oxidation of linoleic acid by lipoxygenase), but 388.24% increase in acetic acid and 184.84% hexanal (direct products of 13-LOX). These results indicate that r9-LOX1 positively regulates the amount of nonanal but negatively regulates acetic acid and hexanal. The negative regulation may be due to a mechanism of negative feedback between LOX family members. The information will help comprehensively understand the function of the bran/seed-specific LOXs, r9-LOX1, and improve the storage quality in the future.
authors.affiliation: Department of Horticulture, Washington State University, Pullman, WA 99164, USA.
authors.forename: Moytri
authors.initials: M
authors.lastname: RoyChowdhury
authors.affiliation: State Key Lab of Rice Biology, International Atomic Energy Agency Collaborating Center, Zhejiang University, Hangzhou, Zhejiang 310029, China; Zhejiang Academy of Agricultural Sciences, Hangzhou, Zhejiang 310021, China.
authors.forename: Xiaobai
authors.identifier: 0000-0001-9615-3543
authors.initials: X
authors.lastname: Li
authors.affiliation: Agricultural Extension Extending Stations, Shaoxing & Zhuji Agricultural Bureau, Shaoxing, Zhejiang 312000, China.
authors.forename: Hangying
authors.initials: H
authors.lastname: Qi
authors.affiliation: Institute for Wheat Research, Henan Academy of Agricultural Sciences, Zhengzhou, Henan 450002, China.
authors.forename: Wenxu
authors.initials: W
authors.lastname: Li
authors.affiliation: State Key Lab of Rice Biology, International Atomic Energy Agency Collaborating Center, Zhejiang University, Hangzhou, Zhejiang 310029, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Sun
authors.affiliation: Agricultural Extension Extending Stations, Shaoxing & Zhuji Agricultural Bureau, Shaoxing, Zhejiang 312000, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Huang
authors.affiliation: State Key Lab of Rice Biology, International Atomic Energy Agency Collaborating Center, Zhejiang University, Hangzhou, Zhejiang 310029, China.
authors.forename: Dianxing
authors.initials: D
authors.lastname: Wu
mesh_terms: D019342:Acetic Acid / Q000494:pharmacology; D000447:Aldehydes / Q000494:pharmacology; D002523:Edible Grain / Q000235:genetics / Q000254:growth & development; D025461:Feedback, Physiological; D018506:Gene Expression Regulation, Plant; D006801:Humans; D058945:Lipoxygenases / Q000235:genetics*; D012275:Oryza / Q000201:enzymology / Q000235:genetics*; D018384:Oxidative Stress / Q000235:genetics; D030821:Plants, Genetically Modified / Q000235:genetics; D018087:Plastids / Q000201:enzymology / Q000235:genetics; D034622:RNA Interference
chemical_list: D000447:Aldehydes; C010463:n-hexanal; D058945:Lipoxygenases; D019342:Acetic Acid