mutation at the splicing receptor site affected RNA splicing and decreased amylose content in barley.

Granule-bound starch synthase I (HvGBSSI) is encoded by the barley () gene and is the sole enzyme in the synthesis of amylose. Here, a mutant was identified from an ethyl methane sulfonate (EMS)-mutagenized barley population. There were two single-base mutations G1086A and A2424G in in the mutant (M2-1105). The G1086A mutation is located at the 3' splicing receptor (AG) site of the fourth intron, resulting in an abnormal RNA splicing. The A2424G mutation was a synonymous mutation in the ninth intron. The pre-mRNA of was incorrectly spliced and transcribed into two abnormal transcripts. The type I transcript had a 6 bp deletion in the 5' of fifth exon, leading to a translated HvGBSSI protein lacking two amino acids with a decreased starch-binding capacity. In the type II transcript, the fourth intron was incorrectly cleaved and retained, resulting in the premature termination of the barley gene. The mutations in the decreased the enzymatic activity of the HvGBSSI enzyme and resulted in a decreased level in amylose content. This work sheds light on a new gene inaction mechanism.