Abstract
Resistant starch (RS) shows several health benefits. Enhancing the RS content of wheat is of major commercial importance. However, knowledge regarding the RS synthesis mechanism in wheat remains limited. In this study, the dynamic accumulation of RS during the filling process in two wheat (Triticum aestivum L.) genotypes with contrasting RS contents (H242, high RS content; H189, low RS content) were investigated. The results demonstrate that beyond 25 days after pollination (DAP), the RS content of H189 was relatively stable, but that of H242 continued to increase. Secondary accumulation was observed in the high-RS-content wheat genotype. A comparative transcriptome analysis between H242 and H189 at 20 DAP and 35 DAP showed that the differentially expressed genes were mainly involved in glycerolipid metabolism, glycerophospholipid metabolism and glucuronate interconversions. Furthermore, weighted gene coexpression network analysis suggested that lipid metabolic pathways such as the glycerophospholipid metabolism pathway might be involved in RS synthesis, and lipid-related genes upregulated beyond 25 DAP resulted in RS secondary accumulation. This work provides insight into the characteristics and mechanisms of RS synthesis.
Highlights
Resistant starch (RS) is defined as the portion of starch that passes undigested through the small intestine of healthy individuals [1]
The thousand-grain weight (TGW) accumulation rate of the two cultivars reached a maximum at 15–20 days after pollination (DAP) (2.171 g day-1 in H242, 2.047 g day−1 in H189) and decreased (Table 1)
No significant differences in the TGW accumulation rate were observed between H242 and H189 in the early (0–10 DAP) and late stages (30–40 DAP) of grain filling (p < 0.05), but there were significant differences between the two cultivars at 10–30 DAP (p < 0.05)
Summary
Resistant starch (RS) is defined as the portion of starch that passes undigested through the small intestine of healthy individuals [1]. RS has been classified as RS1 (physically embedded starch), RS2 (natural starch granules), RS3 (retrograde starch), RS4 (chemically modified starch) or RS5 (five-type self-assembled-starch complexes). RS5 was redefined as five-type self-assembledstarch complexes, such as amylose–lipid, starch–fatty, starch–monoglycerides and starch– lipid protein [7]. The amylose–lipid complexes are commonly found in both native starch granules and processed starch [9]. Starch can be assembled into RS in vitro by adding vitro lipids [10]. The amylose–lipid complex can affect white rice RS content [13]. These studies suggest that lipids play an important role in starch properties. The relationship between lipidic pathways and RS synthesis needs to be further explored during grain development
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