Abstract
Cereal crops with inhibition expression of starch branching enzyme (SBE) contain highly resistant starch in the endosperm, and have potential health benefits for human. However, seed plumpness is significantly different, with different inhibition effects of SBE expression, resulting in differently shrunken seeds. In this study, a transgenic resistant starch rice line, which has highly resistant starch and is developed through inhibition expression of SBEs, had non-, slightly, and moderately shrunken seeds with plumpness from high to low. The differently shrunken seeds had significantly different seed weight and starch content. Different morphological starch granules were detected in the endosperm and had similar spatial distribution pattern among the non-, slightly, and moderately shrunken seeds. Starches from differently shrunken seeds had similar amylose content and amylopectin structure. The protein amount of amylose/amylopectin synthesis key enzymes in endosperm was no different between differently shrunken seeds. The primary branch of the panicle had a higher percentage of non-shrunken seeds than did the secondary branch at the same part of the panicle. From the upper part to the base of the panicle, non-shrunken seeds gradually decreased but slightly and moderately shrunken seeds gradually increased. The above results indicated that the differently shrunken seeds in transgenic rice line had the same SBE dosage, and the starch morphology and structure had no relationship with seed plumpness. The grain position on the panicle influenced seed plumpness, but had no effect on starch properties.
Highlights
Starch is the main component of cereal endosperm
Grains were dehulled by hands, and the resulting seeds were used to investigate seed characteristics, starch morphology and structure, and the protein amount of key amylose/amylopectin synthesis enzymes
Though the differently shrunken expression have different starch morphology and structure [11,32], the present results indicated that seeds from different transgenic lines with inhibition of expression have different starch starch morphology and structure had no relationship with seed plumpness
Summary
Starch is the main component of cereal endosperm. Its content and properties determine the quality and utilization of cereal crops. Starch contains rapidly digestible starch, slowly digestible starch, and resistant starch (RS) according to its digestion rate. RS is a portion of starch that cannot be degraded in the upper gastrointestinal tract but functions as a substrate for bacterial fermentation in the large intestine [1]. RS can provide many health benefits for humans. RS-enriched food can lower the glycemic and insulin responses and reduce the risk of developing obesity, cardiovascular diseases, and type II diabetes [2,3,4]. Normal cereal crops contain very low RS in endosperm
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