背景回顾：Grasses are among the most resilient plants, and some can survive prolonged desiccation in semiarid regions with seasonal rainfall. 

提出问题：However, the genetic elements that distinguish grasses that are sensitive versus tolerant to extreme drying are largely unknown. 

方法手段：Here, we leveraged comparative genomic approaches with the desiccation-tolerant grass Eragrostis nindensis and the related desiccation-sensitive cereal Eragrostis tef to identify changes underlying desiccation tolerance. These analyses were extended across C4 grasses and cereals to identify broader evolutionary conservation and divergence.

初步发现：Across diverse genomic datasets, we identified changes in chromatin architecture, methylation, gene duplications, and expression dynamics related to desiccation in E. nindensis. 

先验假设：It was previously hypothesized that transcriptional rewiring of seed desiccation pathways confers vegetative desiccation tolerance. 

结果解析：Here, we demonstrate that the majority of seed-dehydration–related genes showed similar expression patterns in leaves of both desiccation-tolerant and -sensitive species. However, we identified a small set of seed-related orthologs with expression specific to desiccation-tolerant species.

结论总结：This supports a broad role for seed-related genes, where many are involved in typical drought responses, with only a small subset of crucial genes specifically induced in desiccation-tolerant plants.

摘  要

草类植物是最具韧性的植物之一，其中一些甚至能够在季节性降雨的半干旱地区长时间干燥环境条件下生存。然而，目前对于草本植物中控制对极端干燥的敏感性和耐受性的遗传原件的认识还存在较大的空白。本文中，作者对画眉草属（Eragrostis）的两个植物物种进行了比较基因组学的分析。其中，Eragrostis nindensis是多年生画眉草，对干燥具有耐受性；而Eragrostis tef是一年生画眉草，又名苔麸，是一种谷物，对干燥敏感。作者旨在通过对这两个物种的比较基因组分析鉴定潜在的干燥抗性相关基因。并且，作者进一步将该分析扩展得到了C4草本植物和谷类作物，以鉴定更加广泛的演化保守性与分化。在不同的基因组数据集中，作者鉴定了Eragrostis nindensis中与干燥相关的染色质结构、甲基化、基因复制以及表达动态。先前的研究假设，种子干燥途径的转录重塑赋予了营养器官干燥耐受性。本文中，作者揭示了大多数种子干燥相关的基因在干燥耐受性与干燥敏感型的物种叶片中存在类似的表达模式。然而，作者鉴定到了一小部分的种子相关同源基因特异地在干燥耐受性物种中表达。这些结果揭示了种子相关基因更加广泛的作用，其中大多数的种子相关基因参与典型的干旱响应，而小部分的基因特异性地在干燥耐受性植物中存在。

Significance

Desiccation tolerance likely evolved independently several times in grasses, providing an ideal comparative system to identify genetic elements controlling this trait. Using comparative genomics, we identified genomic and expression changes distinguishing the desiccation-tolerant grass Eragrostis nindensis from its desiccation-sensitive crop relative Eragrostis tef. We expanded these analyses to include several cereals to identify broadly conserved and divergent patterns during water stress. We found that the distinction between drought and desiccation in grasses is subtle, where genes with essential roles in seed development are broadly expressed under water stress. Thus we propose that seeds and leaves share common sets of coregulated genes of likely ancient origin, with only a few genes uniquely expressed for desiccation tolerance.

干燥耐性可能在草类植物中独立演化了多次，为鉴定植物中干燥耐性相关遗传元件提供了一个理想的比较系统。利用比较基因组学，本文作者鉴定了能够区分干燥耐受型草本Eragrostis nindensis与其近缘干燥敏感性谷物Eragrostis tef的基因组和表达变化。作者进一步将该分析扩展到了更多的谷类作物，鉴定了水分胁迫下更加广泛的保守和分化模式。作者发现草本中干旱和干燥的区别比较微小，在种子发育过程中具有关键作用的基因在水分胁迫下具有广泛的表达。因此，作者推测种子和叶片共享了可能起源于共同祖先的共调控基因，而仅只有一小部分的基因特异性地作用于干燥耐受性。