Effects of a novel loss-of-function waxy endosperm allele on sorghum seed development and grain quality

Waxy sorghum seeds, defined by reduced amylose content in starch, offer the potential for improving grain quality in food and industrial applications. While waxy endosperms arising from a nonfunctional waxy (wx) allele leading to the absence of granule-bound starch synthase enzyme have been identified in sorghum, their broader effects on seed development and grain quality remain inadequately understood. To address this gap, we identified a novel wx loss-of-function allele, "wxe" in the mutant population of the sorghum reference genome line BTx623. Beyond reduced amylose content, wxe exhibited increased kernel hardness, elevated protein content, reduced endosperm-to-germ ratio, and decreased kernel weight compared to the wild-type. Integrating transcriptomic, metabolomic, and seed chemistry analyses revealed coordinated regulatory changes during seed development due to disrupted amylose synthesis. This included altered starch granule structure, enhanced lipid profiles, and reduced carbohydrate content. Differentially expressed genes and transcription factors related to starch metabolism provided insights into the regulatory mechanisms. Furthermore, metabolic profiling showed significant changes in the accumulation of compounds influencing flavor and nutritional properties. This study enhances our understanding of the molecular coordination of sorghum seed development and provides new insights into regulating seed development.