Powdery mildew (PM) caused by Blumeria graminis (DC.) Golovin ex Speer f. sp. hordei Marchal (Bgh) is one of the major yield reducing diseases in hulless barley (Hordeum vulgare L. var. nudum Hook. f.). Genotypes with contrasting resistance to PM offer unique opportunities to explore the transcriptome in order to understand the expression changes in genes and pathways. In this study, we explored the phytohormone levels and transcriptome of a Bgh susceptible (XL19) and resistant (ZYM1288) hulless barley genotypes at 0, 5, 12, 24, and 36 h post infection (hpi) with Bgh. We found relatively higher levels of abscisic acid, jasmonic acid, salicylic acid, and cytokinins in ZYM1288. The transcriptome analyses identified 31,354 genes that were enriched in signaling, energy, and defense related pathways. Higher numbers of differentially expressed genes (DEGs) were found in XL19 as compared to ZYM1288 after 5 (3603 vs. 2341) and 12 hpi (3530 vs. 2416). However, after 24 and 36 hpi, the number of DEGs was higher in ZYM1288 as compared to XL19 i.e., 3625 vs. 3034 and 5855 vs. 2725, respectively. Changes in hormone levels drove downstream expression changes in plant-hormone signaling that helped ZYM1288 to perform better under Bgh infection. The expression of DEGs in MAPK-signaling and Toll-like receptor signaling pathways, glucosinolate biosynthesis, glutathione metabolism, brassinosteroid metabolism, and energy related pathways indicated their common roles in defense against PM. Key genes related to PM-resistance were upregulated in the resistant genotype. These genes provide key information towards differences in both genotypes towards resistance to PM. The transcriptomic signatures explored in this study will broaden our understanding towards molecular regulation of resistance to PM in hulless barley.

中文翻译：

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无壳大麦叶对白粉病感染的植物激素和转录组反应

由Blumeria graminis (DC.) Golovin ex Speer f.引起的白粉病 (PM) 。sp. hordei Marchal ( Bgh ) 是大麦 ( Hordeum vulgare L. var. nudum Hook. f.)的主要减产病害之一。对 PM 具有对比抗性的基因型为探索转录组以了解基因和通路的表达变化提供了独特的机会。在这项研究中，我们探索了Bgh易感性 (XL19) 和抗性 (ZYM1288) 无壳大麦基因型在感染 Bgh 后 0、5、12、24 和 36 小时 (hpi)的植物激素水平和转录组. 我们在 ZYM1288 中发现了相对较高水平的脱落酸、茉莉酸、水杨酸和细胞分裂素。转录组分析确定了 31,354 个富含信号、能量和防御相关通路的基因。与 ZYM1288 相比，在 5 hpi（3603 对 2341）和 12 hpi（3530 对 2416）后，在 XL19 中发现了更多的差异表达基因（DEG）。然而，在 24 和 36 hpi 后，与 XL19 相比，ZYM1288 中的 DEG 数量更高，即分别为 3625 对 3034 和 5855 对 2725。激素水平的变化推动了植物激素信号的下游表达变化，这有助于 ZYM1288 在Bgh下表现更好感染。DEGs 在 MAPK 信号通路和 Toll 样受体信号通路、芥子油苷生物合成、谷胱甘肽代谢、油菜素类固醇代谢和能量相关通路中的表达表明它们在防御 PM 中的共同作用。与 PM 抗性相关的关键基因在抗性基因型中上调。这些基因提供了关于两种基因型对 PM 抗性差异的关键信息。本研究中探索的转录组学特征将拓宽我们对无壳大麦抗 PM 分子调控的理解。