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Accumulation and deposition of triacylglycerols in the starchy endosperm of wheat grain
A combination of lipidomics, transcriptomics and bioimaging has been used to study triacylglycerol synthesis and deposition in the developing starchy endosperm of wheat. The content of TAG increased between 14 and 34 days after anthesis, from 50 to 115 mg/100 g dry wt and from about 35 to 175 mg/100 g dry wt in two experiments. The major fatty acids were C16 (palmitic C16:0 and palmitoleic C16:1) and C18 (stearic C18:0, oleic C18:1, linoleic C18:2 and linolenic C18:3), with unsaturated fatty acids accounting for about 75â80% of the total throughout development. Linoleic acid (C18:2) was the major component at all stages and the proportion increased during development. Transcript profiling indicated that predominant route to TAG synthesis and oil accumulation is via the Kennedy pathway and diacylglycerol acyltransferase (DGAT) activity. Confocal microscopy of stained tissue sections showed that TAG accumulated in droplets which are associated with protein and concentrated in the starchy endosperm cells below the sub-aleurone cells. Transcripts encoding 16kd oleosins were also expressed, indicating that the oil droplets are in part stabilised by oleosin proteins
Effects of Cultivar and Nitrogen Nutrition on the Lipid Composition of Wheat Flour
Despite
being minor components of flour, wheat (Triticum aestivum L.) lipids contribute to grain
processing. They are particularly important for bread making, where
they adsorb to the surface of gas bubbles formed during the proving
stage of bread making, stabilizing the gas cells and improving gas
retention within the dough. This contributes to the volume and texture
of the loaf. However, little is understood about how their amount,
composition, and properties vary in response to genotype (G), environment
(E) or G Ă E interactions. Six wheat lines were therefore grown
at three levels of nitrogen supply at Rothamsted Research, and 48
lipid species across six lipid classes were identified and quantified
in white flour using electrospray ionizationâtandem triple
quadrupole mass spectrometry (ESIâMS/MS). This showed clear
differences in the contents and compositions of lipids between cultivar
as well as effects of nitrogen fertilization, which would be expected
to have impacts on the processing properties of the samples