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Grain-specific reduction in lipoxygenase activity improves flour color quality and seed longevity in common wheat

Update time: 10/31/2016

In higher plants, lipoxygenases (LOXs) catalyze the oxidation of polyunsaturated fatty acids and can accumulate to relatively high levels in the seeds. However, high LOX activity has often been found associated with harmful effects on the quality attributes and the longevity of harvested seeds. Here, we report the development and characterization of three homozygous T-5 transgenic lines (designated as LOXRNAi-4, 7 and 9, respectively) with LOX activity specifically reduced in the grains of common wheat. An RNAi hairpin directed under an endosperm-specific promoter was introduced into the genome of the elite wheat variety Longchun 23 using particle bombardment. Each transgenic line (LOXRNAi-4, 7 or 9) derived from separate integration event, which carried more than 20 copies of the transgene. The three LOXRNAi lines and wild-type (WT) Longchun 23 showed a similar level of LOX transcripts in the flag leaves. However, relative to WT control, LOXRNAi-4, 7 and 9 exhibited drastic decreases in the level of LOX transcripts during grain development compared with WT control. The LOX activity levels in the harvested grains of the three transgenic lines were significantly lower than that of WT control under either normal conditions or artificial aging (AA, stored at 40 degrees C and 85 % humidity for 6 or 9 days) treatment. The whiteness values of the flour samples from LOXRNAi-4, 7 and 9 were generally and significantly higher than those of WT control regardless of the grains were stored under normal or AA conditions. Furthermore, the germination rates of LOXRNAi-4, 7 and 9 were substantially higher than those of WT control under AA treatment. Our data demonstrate that grain-specific reduction in LOX activity by RNAi may represent a generally applicable approach for improving the quality traits and longevity of crop seeds.