Summary
Awns of wild barley (Hordeum vulgare ssp. spontaneum L.) are rough by default due to silicified upward-oriented trichomes on the awn's epidermis, forming a ratcheted surface, which is advantageous for seed dispersal and burial. Cultivated barley, however, may carry smooth awns covered by smaller barbs or lacking barbs completely. The gene Raw1 on chromosome 5H is a major factor controlling barley awn roughness and was shown to encode a LONG AND BARBED AWN1 (LABA1) homolog. Here we report, by using quantitative analysis of the barb trait, map-based cloning and Cas9-mediated gene knock-out, a second gene Raw7, located on barley chromosome 7H, encoding a putative two-component response regulator. We propose that Raw7 acts downstream of Raw1 in a cytokinin signaling pathway underlying cell cycle control in epidermal barb primordia cells. Raw1 and Raw7 show epistatic interaction, suggesting that Raw1 acts as the primary driver of barb initiation, while Raw7 modulates barb size and frequency. Our findings provide the foundation to study the selection and domestication history of the awn roughness trait in barley, and thus to dissect if awn roughness is providing an advantage in cultivated barley or if the trait persisted after domestication due to linkage drag.
Outcomes reported
Awns of wild barley (Hordeum vulgare ssp. spontaneum L.) are rough by default due to silicified upward-oriented trichomes on the awn's epidermis, forming a ratcheted surface, which is advantageous for seed dispersal and burial. Cultivated barley, however, may carry smooth awns covered by smaller barbs or lacking barbs completely. The gene Raw1 on chromosome 5H is a major factor controlling barley awn roughness and was shown to encode a LONG AND BARBED AWN1 (LABA1) homolog. Here we report, by using quantitative analysis of the barb trait, map-based cloning and Cas9-mediated gene knock-out, a second gene Raw7, located on barley chromosome 7H, encoding a putative two-component response regulator. We propose that Raw7 acts downstream of Raw1 in a cytokinin signaling pathway underlying cell cycle control in epidermal barb primordia cells. Raw1 and Raw7 show epistatic interaction, suggesting that Raw1 acts as the primary driver of barb initiation, while Raw7 modulates barb size and frequency. Our findings provide the foundation to study the selection and domestication history of the awn roughness trait in barley, and thus to dissect if awn roughness is providing an advantage in cultivated barley or if the trait persisted after domestication due to linkage drag.
Dig deeper with Pulse AI.
Pulse AI has read the whole catalogue. Ask about this record, its theme, or how the findings apply to UK farming and policy — every answer cites the underlying studies.