Genetic control of barb/trichome formation on barley awns and stigmata – or, why does cultivated barley need rough awns?

大麦芒很粗糙，因为它们被高度硅化的倒刺所覆盖。众所周知，粗糙的草皮会在谷物收获期间对人类呼吸道造成危害，也会对一些反刍动物和其他动物在觅食大麦时的消化道造成危害。这种性状是由几个主要的遗传位点控制的，培育无刺芒或光滑芒相对容易实现。由于光滑的芒与柱头茸毛减少相关，这通常与大麦的生育力降低有关，然而，粗糙的芒仍然是栽培大麦的主要形式。我们最近克隆了一个控制大麦粗糙度的主基因Raw1，并基于GWAS和双亲本定位在大麦染色体7HS上一个有前景的区域划定了第二个基因座。我们的目标是通过最先进的基于基因组学的定位克隆分离第二个位点，并对克隆的两个芒糙基因进行基因功能分析。了解自然选择下的两个基因，利用我在IPK的团队正在开发的泛基因组和遗传多样性资源，将有可能跟踪芒粗糙性状的选择/驯化历史，并测试其与柱头茸毛和育性的联系/相关性，从而为未来培育光滑芒表型提供知识，而不会因育性降低而导致产量损失。该项目旨在揭示大麦芒糙性的遗传基础及其与柱头茸毛的相关性，从而影响其育性和产量。•大麦染色体7HS （Raw7HS）光滑芒位点的遗传定位和功能基因的克隆；•通过TILLING和定点突变验证新分离基因Raw7HS的功能；•Raw1通过定点诱变控制芒的粗糙度和柱头茸毛的功能验证；•揭示Raw1和Raw7HS位点的自然多样性和选择特征；•通过对自然多样性收集的粗糙、光滑和半光滑材料进行系统表型分析，测试倒刺形成与柱头茸毛之间的功能联系；•一组独立诱导的光滑/半光滑突变体的表型和基因型（Raw1和Raw7HS）特征揭示了它们的等位基因状态。•在raw1和raw7HS基因型和诱导突变体之间建立遗传杂交，以测试累积或上位性相互作用，并建立定位群体，以便在后续项目中进一步进行基因分离。

Barley awns are rough because they are coated with highly silicified barbs. Rough awns are known to cause hazards for the human respiratory tract during grain harvest as well as for the digestive tract of some ruminants and other animals when foraging on barley. The trait is controlled by a few major genetic loci and breeding for barbless awns, or smooth awns, is relatively easy achievable. Because of a correlation of smooth awns with reduced stigma hairiness, which is often associated with reduced fertility in barley, however, rough awn remained the predominant form of cultivated barley.We have recently cloned a major gene Raw1 controlling awn roughness in barley and based on GWAS and bi-parental mapping we have delimited a second locus in a promising region for gene-cloning on barley chromosome 7HS.We aim to isolate the second locus by state-of-the-art genomics-based positional cloning and perform gene function analysis of both cloned awn roughness genes. Knowing both genes that were under natural selection and by exploiting the pan-genome and genetic diversity resources under development in my group at IPK, it will be possible to track the selection/domestication history of the trait awn roughness and test its linkage/correlation with stigma hairiness and fertility and thus provide the knowledge of future breeding for smooth awn phenotypes without yield penalty through reduced fertility. The project aims at revealing the genetic basis of awn roughness in barley as well as its correlation to stigma hairiness, which is influencing fertility and yield. The following objectives will be adressed:• Genetic mapping and cloning of the functional gene of the newly identified smooth awn locus on barley chromosome 7HS (Raw7HS);• Functional validation of the newly isolated gene Raw7HS by TILLING and site-directed mutagenesis;• Functional validation of Raw1 control of awn roughness and stigma hairiness through site-directed mutagenesis;• Reveal natural diversity and signatures of selection at the Raw1 and Raw7HS loci; • Test for functional linkage between barb formation and stigma hairiness through systematic phenotyping of rough, smooth and semi-smooth accessions from a natural diversity collection;• Phenotypic and genotypic (Raw1 and Raw7HS) characterisation of a panel of independently induced smooth / semi-smooth mutants to reveal their allelic state.• Establish genetic crosses between raw1 and raw7HS genotypes and the panel of induced mutants to test for cumulative or epistatic interactions and to establish mapping populations for further gene isolations in (a) subsequent project(s).