Mobilization of lipid reserves during germination of oat (Avena sativa L.), a cereal rich in endosperm oil

Abstract

Since the cereal endosperm is a dead tissue in the mature grain, β-oxidation is not possible there. This raises the question about the use of the endosperm oil in cereal grains during germination. In this study, mobilization of lipids in different tissues of germinating oat grains was analysed using thin-layer and gas chromatography. The data imply that the oat endosperm oil [triacylglycerol (TAG)] is not a dead-end product as it was absorbed by the scutellum, either as free fatty acids (FFAs) released from TAG or as intact TAG immediately degraded to FFAs. These data were supported by light and transmission electron microscopy (LM and TEM) studies where close contact between endosperm lipid droplets and the scutellum was observed. The appearance of the fused oil in the oat endosperm changed into oil droplets during germination in areas close to the aleurone and the scutellar epithelium. However, according to the data obtained by TEM these oil droplets are unlikely to be oil bodies surrounded by oleosins. Accumulation of FFA pools in the embryo suggested further transport of FFAs from the scutellum. Noticeably high levels of TAG were also accumulated in the embryo but were not synthesized by re-esterification from imported FFAs. Comparison between two oat cultivars with different amounts of oil and starch in the endosperm suggests that an increased oil to starch ratio in oat grains does not significantly impact the germination process.

Spatial Mapping and Profiling of Metabolite Distributions during Germination

“…wheat [Triticum aestivum] and oat [Avena sativa]) that store oil in the endosperm (Leonova et al, 2010). The embryonic localization of four TAG species differing in fatty acyl chain composition is shown in Figure 3B.…”

Oat (<i>Avena sativa</i> L.): Oil and Nutriment Compounds Valorization for Potential Use in Industrial Applications

“…Yet, Leonova et al 48 who studied lipid reserves mobilization in different tissues during oat germination Avena sativa L. proved by transmission electron microscopy that the oil droplets which appeared in areas close to the scutellar epithelium and the aleurone of oat grain were oil bodies surrounded by oleosins. Oleosins stabilize and prevent oil bodies fusion and contribute to facilitate lipase activity to rapidly mobilize fatty acids during oil seeds germination 49,50 .…”

“…Oleosins stabilize and prevent oil bodies fusion and contribute to facilitate lipase activity to rapidly mobilize fatty acids during oil seeds germination 49,50 . Oil seeds storage constitutes a form of energy triacylglycerol TAG which can be mobilized by the action of lipases which release free fatty acids FFAs from this oil and can be degraded under β-oxidation and glyoxylate cycles and which are subsequently converted into sugars 48,51,52 . But the cereal endosperm is known to be a dead tissue in the mature grain, so this β-oxidation does not occur there.…”

Short Communication. Effect of phosphorus nutrition and grain position within maize cob on grain phosphorus accumulation

“…For optimum crop yield, plants require adequate P from very early growth stages Grant et al, 2001). The success or failure of the early growth stage of developing seedlings is directly related to successful remobilization of stored grain P reserves that were accumulated throughout the ripening period (Guardiola & Sutcliffe, 1971;Le Deunff, 1975;Lawrence et al, 1990;Leonova et al, 2010;Nadeem et al, 2011Nadeem et al, , 2012a. As the hydrolysis of grain P during germination is a major source of inorganic P to support the growing seedlings during early growth stages (Nadeem et al, 2011;2012b) therefore the present study was conducted to investigate the role of P nutrition to the parent plant on the dry weight and P reserves accumulation in maize grains for better selection of seeds.…”