Effects of a novel Loss-of-function waxy endoperm allele on Sorghum Seed Development and Grain Quality

Authors: DHIMAN, PALLAVI - Texas Tech University; SOUMEN, SHEJAL - Texas Tech University; NIGAM, DEEPTI - Texas Tech University; Bean, Scott; Wu, Xiaorong; PATIL, GUNVANT - Texas Tech University; XIN, ZHANGUO - US Department Of Agriculture (USDA); YINPING, JIAO - Texas Tech University

Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2025
Publication Date: 8/28/2025
Citation: Dhiman, P., Soumen, S., Nigam, D., Bean, S.R., Wu, X., Patil, G.B., Xin, Z., Yinping, J. 2025. Effects of a novel Loss-of-function waxy endoperm allele on Sorghum Seed Development and Grain Quality. Journal of Experimental Botany. https://doi.org/10.1093/g3journal/jkaf177.
DOI: https://doi.org/10.1093/g3journal/jkaf177

Interpretive Summary: In grains such as sorghum, starch is an important source of carbohydrates and plays a key role in human food, livestock feed, and ethanol production for the brewing and biofuel industry. Starch has two main components, amylose and amylopectin. Waxy starch has low levels of amylose and has unique functional properties in foods, ferments faster than starch and has higher digestibility compared to starch with higher levels of amylose. While the genetic changes resulting in waxy sorghum have been identified their broader effects on seed development and grain quality remain poorly understood. To address this gap in knowledge, novel waxy sorghum lines were studied during seed development. The waxy sorghum lines showed the expected reduced amylose content, but also increased kernel hardness, larger starch granules and higher protein levels. This study provides additional information on waxy sorghum grain quality overall and provides a comprehensive molecular framework for developing improved waxy sorghum varieties, providing sorghum producers and the sorghum industry with new tools for developing value-added sorghum lines.

Technical Abstract: The waxy endosperm in sorghum, defined by reduced amylose content in starch, offers potential for improving grain quality in both food and industrial applications. While waxy mutants arising from non-functional GBSS1 alleles 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 GBSS1 knockout allele, "Sbwxe," in the sorghum reference genome line BTx623. Beyond reduced amylose content, this mutant exhibited increased kernel hardness, enlarged starch granules, and elevated protein content. Utilizing this genetic background, we employed integrated transcriptomic, metabolomic, and seed chemistry approaches to uncover the regulatory consequences of disrupted amylose synthesis. Notable findings include structural modifications in starch granules, enhanced lipid profiles, reduced carbohydrate content, and reprogramming of starch and protein biosynthetic pathways. Differentially expressed genes and transcription factors associated with starch metabolism shed light on the molecular mechanisms underlying the waxy phenotype. Additionally, metabolic profiling revealed significant changes in pathways influencing flavor and nutritional properties. This study provides a comprehensive molecular framework for developing improved waxy sorghum varieties, addressing critical gaps in understanding seed development and grain quality regulation.