Analysis of starch structure, functional properties, and the underlying molecular mechanism in SeaRice86 (SR86)

Starch, the principal carbohydrate in rice, governs functional attributes critical to food processing and nutritional value. This study compares structural, functional, and molecular traits of starch from salt-tolerant SeaRice86 (SR86) and conventional Huanghuazhan (HHZ). Structural analysis revealed SR86 starch exhibits a distinct A-type crystal structure with higher crystallinity at 12 DAF but lower values at 24 DAF. FTIR spectroscopy showed reduced short-range molecular ordering in SR86 starch. Functional assessments demonstrated that SR86 possesses elevated breakdown viscosity and reduced final viscosity, correlating with its lower amylose content and diminished retrogradation tendency. Transcriptomic profiling identified key molecular drivers underlying their starch properties divergences. SR86 exhibited suppressed GBSSI expression, consistent with its lower amylose. Temporal shifts in soluble starch synthase (SS) activity were observed, with peak SS expression occurring later in SR86. Granule size variations corresponded with differential SSI expression, while altered amylopectin chain distribution (DP 25-36) inversely correlated with starch branching enzyme (SBE) activity. Coordinated regulation of isoamylase (ISA1-3) and pullulanase (PUL) genes further contributed to the unique starch architecture. These findings provide a foundation for leveraging SR86 starch in functional food formulations and highlight its potential as a genetic resource for improving starch quality under saline-alkaline cultivation.