Functional Characterization of 9-/13-LOXs in Rice and Silencing Their Expressions to Improve Grain Qualities

Biomed Res Int. 2016:2016:4275904. doi: 10.1155/2016/4275904. Epub 2016 Jun 15.

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.

MeSH terms

  • Acetic Acid / pharmacology
  • Aldehydes / pharmacology
  • Edible Grain / genetics
  • Edible Grain / growth & development
  • Feedback, Physiological
  • Gene Expression Regulation, Plant
  • Humans
  • Lipoxygenases / genetics*
  • Oryza / enzymology
  • Oryza / genetics*
  • Oxidative Stress / genetics
  • Plants, Genetically Modified / genetics
  • Plastids / enzymology
  • Plastids / genetics
  • RNA Interference

Substances

  • Aldehydes
  • n-hexanal
  • Lipoxygenases
  • Acetic Acid