College of Eco-environmental Engineering, Qinghai University, Xining 810016, Qinghai, China.
College of Agriculture and Animal Husbandry, Qinghai University, Xining 810016, Qinghai, China.
Gene. 2025 Jan 20;934:149036. doi: 10.1016/j.gene.2024.149036. Epub 2024 Oct 22.
Awns in barley have different shapes including awnless, straight, hooded, crooked, and leafy awns. The hooded awns are characterized by an appendage of the lemma, which forms a trigonal or cap-shaped structure, and even blossoms and yields fruits on barley awn. In the lemma primordia of wild-type (straight awn), cells divide and elongate to form the straight awn. However, in the lemma primordia of KNOX3 mutant (hooded awn), cells divide at various orientations without elongating, and they form hooded awns. This phenomenon is due to the upregulation of KNOX3 expression via insertion of a tandem direct duplication of 305 bp in the intron IV. Here, we summarize the development of barley hooded awn research in the following two aspects: on the one hand, the morphology, development of hooded awns, and the expression regulation of the KNOX3 gene. The latter includes ectopic expression of the KNOX3 gene, gene interactions among awn-related genes, the regulatory relationship between class I KNOX genes and hormones, as well as the influence of abiotic stresses. On the other hand, the potential performance of hooded awns in barley for yield breeding is discussed. Hooded awns have potential application value in forage, which could compensate for the disadvantage of the long straight awn in the barley straw used for feed in modern cultivars. In addition, the hooded awn produces ectopic meristems to develop complete florets, which is an interesting question and helps to understand the development, adaptation, and evolution of plant floral organs.
大麦的芒具有不同的形状，包括无芒、直芒、帽状芒、钩状芒和叶状芒。帽状芒的特征是外稃的附属物，形成三角形或帽状结构，甚至在大麦芒上开花和结果。在野生型（直芒）的外稃原基中，细胞分裂和伸长形成直芒。然而，在 KNOX3 突变体（帽状芒）的外稃原基中，细胞以不同的方向分裂而不伸长，形成帽状芒。这种现象是由于 KNOX3 基因的表达通过在内含子 IV 中插入 305bp 的串联直接重复而被上调。在这里，我们总结了以下两个方面的大麦帽状芒研究进展：一方面是帽状芒的形态、发育和 KNOX3 基因的表达调控；后者包括 KNOX3 基因的异位表达、与芒相关基因之间的基因相互作用、I 类 KNOX 基因与激素的调控关系以及非生物胁迫的影响。另一方面，讨论了帽状芒在大麦产量育种中的潜在表现。帽状芒在饲料用大麦秸秆的长直芒的现代品种中具有潜在的应用价值。此外，帽状芒产生异位分生组织以发育完整的小花，这是一个有趣的问题，有助于理解植物花器官的发育、适应和进化。
