Pearl millet ( Pennisetum glaucum (L.)) is a vital cereal crop renowned for its ability to thrive in challenging environmental conditions; however, the molecular mechanisms governing its salt stress tolerance remain poorly understood. To address this gap, next-generation RNA sequencing was conducted to compare gene expression patterns in pearl millet seedlings exposed to salt stress with those grown under normal conditions. Our RNA sequencing analysis focused on shoots from 13-day-old pearl millet plants subjected to either salinity stress (150 mmol of NaCl for 3 days) or thermal stress (50°C for 60 s). Of 36,041 genes examined, 17,271 genes with fold changes ranging from 2.2 to 19.6 were successfully identified. Specifically, 2388 genes were differentially upregulated in response to heat stress, whereas 4327 genes were downregulated. Under salt stress conditions, 2013 genes were upregulated and 4221 genes were downregulated. Transcriptomic analysis revealed four common abiotic KEGG pathways that play crucial roles in the response of pearl millet to salt and heat stress: phenylpropanoid biosynthesis, photosynthesis–antenna proteins, photosynthesis, and plant hormone signal transduction. These metabolic pathways are necessary for pearl millet to withstand and adapt to abiotic stresses caused by salt and heat. Moreover, the pearl millet shoot heat stress group showed specific transcriptomics related to KEEG metabolic pathways such as cytochrome P450, cutin, suberine, and wax biosynthesis, zeatin biosynthesis, crocin biosynthesis, ginsenoside biosynthesis, saponin biosynthesis, and biosynthesis of various plant secondary metabolites. In contrast, pearl millet shoots exposed to salinity stress exhibited transcriptomic changes associated with KEEG metabolic pathways related to carbon fixation in photosynthetic organisms, mismatch repair, and nitrogen metabolism. Our findings underscore the remarkable cross-tolerance of pearl millet to simultaneous salt and heat stress, elucidated through the activation of shared abiotic KEGG pathways. This study emphasizes the pivotal role of transcriptomics analysis in unraveling the molecular responses of pearl millet under abiotic stress conditions.

中文翻译：

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珍珠粟的非生物胁迫耐受性：通过转录组学揭示分子机制

珍珠粟 (Pennisetum glaucum (L.)) 是一种重要的谷类作物，以其在充满挑战的环境条件下茁壮成长的能力而闻名；然而，人们对其盐胁迫耐受性的分子机制仍知之甚少。为了解决这一差距，我们进行了新一代 RNA 测序，以比较暴露于盐胁迫下的珍珠粟幼苗与正常条件下生长的珍珠粟幼苗的基因表达模式。我们的 RNA 测序分析主要针对 13 天大的珍珠粟植物的芽，这些植物受到盐度胁迫（150 mmol 氯化钠，持续 3 天）或热胁迫（50°C，持续 60 秒）。在检查的 36,041 个基因中，成功鉴定了 17,271 个倍数变化范围为 2.2 至 19.6 的基因。具体来说，2388 个基因因热应激而差异上调，而 4327 个基因则下调。盐胁迫条件下，2013个基因上调，4221个基因下调。转录组分析揭示了四种常见的非生物 KEGG 途径，它们在珍珠粟对盐和热胁迫的响应中发挥着至关重要的作用：苯丙素生物合成、光合作用-天线蛋白、光合作用和植物激素信号转导。这些代谢途径是珍珠粟承受和适应盐和热引起的非生物胁迫所必需的。此外，珍珠粟芽热胁迫组表现出与KEEG代谢途径相关的特异性转录组学，如细胞色素P450、角质、木栓质和蜡生物合成、玉米素生物合成、藏红花素生物合成、人参皂苷生物合成、皂苷生物合成以及各种植物次生代谢物的生物合成。相比之下，暴露于盐度胁迫的珍珠粟芽表现出与光合生​​物固碳、错配修复和氮代谢相关的KEEG代谢途径相关的转录组变化。我们的研究结果强调了珍珠粟对同时发生的盐和热胁迫的显着交叉耐受性，这是通过共享非生物 KEGG 途径的激活得到阐明的。这项研究强调了转录组学分析在揭示珍珠粟在非生物胁迫条件下的分子反应方面的关键作用。