Dual knockout of 2 starch synthase-related genes drives sugar reprogramming via metabolic rewiring in barley

https://academic.oup.com/plphys/article/198/4/kiaf287/8223065?login=true

Plant Physiology, Volume 198, Issue 4, August 2025, kiaf287

Yi Jiang,Bang Wang,Yulong Li,Qiang Xu,Yazhou Zhang,Huaping Tang,Pengfei Qi,Mei Deng,Jian Ma,Guoyue Chen,Jirui Wang,Yuming Wei,Qiantao Jiang

Extract

Dear Editor,

Barley (Hordeum vulgareL.), the fourth most cultivated cereal globally, stores starch as its predominant seed reserve, accounting for ∼70% of grain weight. Starch consists of amylose, a linear α-1,4-glucan, and amylopectin, a highly branched polymer. Granule-Bound Starch Synthase I (GBSSI encoded by Waxy, also designated as Wx) catalyzes amylose biosynthesis, while Soluble Starch Synthase IIa (SSIIa) elongates short amylopectin chains to optimize starch crystallinity (Seung 2020). The development of gene-editing technologies has enabled substantial advancements in the modification of starch synthase genes (Luo et al. 2021). Single mutations in SSIIa or Waxy have been extensively studied:ssIIamutants accumulate shorter amylopectin chains, altering starch thermal properties (Yang et al. 2024), while wxmutants eliminate amylose, producing “waxy” starch with enhanced digestibility (Li et al. 2024). However, the combinatorial effects of dualssIIa/wx mutations remain underexplored, particularly their synergistic impact on soluble sugar accumulation and starch ultrastructure. This study aims to dissect how dual inactivation of SSIIa and GBSSI reshapes carbohydrate partitioning, offering a model system for exploring metabolic trade-offs between starch and soluble sugar biosynthesis in cereals.