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

Abstract EN

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.