The Generation Gap - Mechanisms of maternal control on grain

了解谷物的粮食生产对于在我们不断变化的世界中保障粮食安全至关重要。大麦是一种广泛种植的全球谷物，对我国具有巨大的经济意义，是一个强大的实验系统，用于识别和描述影响谷物产量和质量的过程。我们最近揭示了大麦中两个主要调控因子的重要性，这两个因子改变了大麦中保护性和营养丰富的母体组织与充满谷物的淀粉和热量丰富的子代组织之间的生长和生存之间的平衡。我们假设，通过限制母体组织的大小并促进它们的消除，将这种平衡从母体组织转移出去，提供了增加谷物大小和重量所需的营养和空间。我们推测，野生大麦和栽培大麦对这种平衡的调节可能不同，这可能解释了栽培大麦的改良籽粒。我们预测，这一过程是通过控制谷物组织中的基因表达和信号传递来发挥作用的，但确切的机制尚不清楚。造成这种认识差距的部分原因是，检验我们的预测很棘手：谷物是这些组织的混合物，调控因素的作用既早又晚，使对组织和特定时间事件及其对谷物的影响的准确评估变得复杂和混乱。我们建议通过在大麦中应用两项前沿技术来克服这些挑战。首先，我们将使用单细胞RNA测序来测量单个细胞内的基因表达，然后计算聚类来建立细胞群体，并分析这些变化在整个谷物发育过程中是如何变化的。其次，我们将应用新的诱导表达系统来改变调控因子在特定时间的活性，以梳理出早期和晚期功能对籽粒参数的重要性。我们还将结合这些方法来评估在特定组织中激活的调节因子对邻近和远处组织中基因表达的影响。最后，我们将探索这些细胞群体在野生大麦和栽培大麦之间的差异，并测试野生和栽培调控因子与谷物参数的功能相关性。综上所述，我们的工作将确定谷物组织的发育轨迹及其对控制母子生长和存活的调控因素的反应，显著促进我们对谷物发育的理解。

Understanding grain production in cereals is vital to safeguard food security in our changing world. Barley is a widely grown global cereal of vast economic importance to our country, and a powerful experimental system to identify and characterise processes that influence grain yield and quality. We recently revealed the importance of two master regulatory factors in barley which alter the balance between growth and survival of protective and nutritive maternal tissues versus the starchy, calorie-rich filial tissues filling the grain. We hypothesise that shifting this balance away from maternal tissues by limiting their size and promoting their elimination, provides the nutrients and space needed to increase grain size and weight. We speculate that the regulation of this balance may differ between wild and cultivated barleys, potentially explaining improved grain of cultivated barley. We predict that this process works by controlling gene expression and signalling across grain tissues, but the exact mechanisms remain unclear. Part of the reason for this knowledge gap is that testing our predictions is tricky: grain is a mix of these tissues and regulatory factors act both early and late, complicating and confounding accurate assessments of tissue and time-specific events and their effects on grain. We propose to surmount these challenges by applying two leading-edge technologies in barley. First, we will use single cell RNA sequencing to measure gene expression within individual cells followed by computational clustering to build cell populations and analysis of how these change throughout grain development. Second, we will apply new inducible expression systems to change the activity of regulatory factors at specific times to tease apart the importance of early versus late functions on grain parameters. We will also combine these approaches to assess the influence of regulatory factors activated in specific tissues on the gene expression in neighbouring and distant tissues. Finally, we will explore how these cell populations differ between wild and cultivated barleys and test the functional relevance of wild and cultivated regulatory factors to grain parameters. Taken together, our work will define the developmental trajectories of grain tissues and their responses to regulatory factors controlling maternal versus filial growth and survival, significantly advancing our understanding of cereal grain development.