Genome editing of five starch synthesis genes produces highly resistant starch and dietary fibre in barley grains

https://onlinelibrary.wiley.com/doi/10.1111/pbi.14324

Plant Biotechnology Journal,28 February 2024

Qiang Yang,Jean-Philippe Ral,Yuming Wei,Youliang Zheng,Zhongyi Li,Qiantao Jiang

Abstract

Resistant starch (RS) refers to starch that is not digested in the stomach or small intestine, and provides health benefits by reducing glycaemic index and promoting gut health (Hazardet al.,2020). Barley (Hordeum vulgare L.) is the fourth most widely cultivated cereal worldwide, and there is growing interest in barley as a healthy food. The RS content of cereal grains is positively associated with the presence of amylose and long-chain amylopectin (Liet al.,2021). However, increasing the levels of amylose in crops is still challenging. Overexpressing the enzyme involved in amylose synthesis, granule-bound starch synthase (GBSS), does not increase amylose content in most species (Seung,2020). By contrast, suppressing amylopectin synthesis enzymes such as starch synthase (SS) and starch-branching enzyme (SBE) isoforms in cereals increases amylose content significantly (Chenet al.,2021). However, knockout mutations in these genes usually compromise the yield potential. Recent progress in CRISPR/Cas9-mediated gene editing make it possible to induce targeted mutations in multiplex genes (Chenget al.,2023; Lawrensonet al.,2015; Luoet al.,2021), which provides a promising approach for devising new strategies to increase amylose content while avoiding/minimizing production limitations. We reasoned that multiplex editing could allow the contribution of all other SS and SBE isoforms to amylose content to be systematically assessed, and allow screening for optimum combinations of mutations that could synergistically provide strong increases in amylose content.