Loss of ADP-glucose transporter in barley sex1 mutant caused shrunken endosperm but with elevated protein and β-glucan content in whole meal

https://www.sciencedirect.com/science/article/pii/S0141813023032610?via%3Dihub

International Journal of Biological Macromolecules, Volume 251, 1 November 2023, 126365

Hang Liu#, Yaya Zou#, Qijing Xuan#, Rong Tian, Jing Zhu, Xiangru Qu, Min Sun, Yanlin Liu, Huaping Tang, Mei Deng, Qiantao Jiang, Qiang Xu, Yuanying Peng, Guoyue Chen, Wei Li, Zhien Pu, Yunfeng Jiang, Jirui Wang, Pengfi Qi, Yazhou Zhang, Youliang Zheng, Yuming Wei*, Jian Ma*

Abstract

Grain shape and plumpness affect barley yield. Despite numerous studies on shrunken endosperm mutants in barley, their molecular mechanism and application potential in the food industry are largely unknown. Here, map-based cloning, co-segregation analyses, and allelic variant validation revealed that the loss of HORVU6Hr1G037950 encoding an ADP-glucose transporter caused the shrunken endosperm in sex1. Haplotype analysis suggested that hap4 in the promoter sequence was positively related to the hundred-grain weight showing a breeding potential. A pair of near-isogenic lines targeting HORVU6Hr1G037950 was produced and characterized to investigate molecular mechanisms that SEX1 regulates endosperm development. Results presented that the absence of the SEX1 gene led to the decrease of starch content and A-type granules size, the increase of β-glucan, protein, gelatinization temperature, soluble sugar content, amylopectin A chains, and B1 chains. Enzymatic activity, transcriptome and metabolome analyses revealed the loss of SEX1 results in an impaired ADP-glucose-to-starch conversion process, consequently leading to higher soluble sugar contents and lower starch accumulation, thereby inducing a shrunken-endosperm phenotype in sex1. Taken together, this study provides new insights into barley grain development, and the elevated protein and β-glucan contents of the whole meal in sex1 imply its promising application in the food industry.