Cotton (Gossypium hirsutum L.) is one of the most important cash crops worldwide. Fine roots are the central part of the root system that contributes to plant water and nutrient uptake. However, the mechanisms underlying the response of cotton fine roots to soil drought remains unclear. To elucidate the proteomic changes in fine roots of cotton plants under drought stress, 70–75% and 40–45% soil relative water content treatments were imposed on control (CK) and drought stress (DS) groups, respectively. Then, tandem mass tags (TMT) technology was used to determine the proteome profiles of fine root tissue samples. Drought significantly decreased the value of average root diameter of cotton seedlings, whereas the total root length and the activities of antioxidases were increased. To study the molecular mechanisms underlying drought response further, the proteome differences between tissues under CK and DS treatments were compared pairwise at 0, 30, and 45 DAD (days after drought stress). In total, 118 differentially expressed proteins (DEPs) were up-regulated and 105 were down-regulated in the ‘DS30 versus CK30’ comparison; 662 DEPs were up-regulated, and 611 were down-regulated in the ‘DS45 versus CK45’ comparison. The functions of these DEPs were classified according to their pathways. Under early stage drought (30 DAD), some DEPs involved in the ‘Cutin, suberin, and wax synthesis’ pathway were up-regulated, while the down-regulated DEPs were mainly enriched within the ‘Monoterpenoid biosynthesis’ pathway. Forty-five days of soil drought had a greater impact on DEPs involved in metabolism. Many proteins involving ‘Carbohydrate metabolism,’ ‘Energy metabolism,’ ‘Fatty acid metabolism,’ ‘Amino acid metabolism,’ and ‘Secondary metabolite biosynthesis’ were identified as DEPs. Additionally, proteins related to ion transport, stress/defense, and phytohormones were also shown to play roles in determining the fine root growth of cotton plants under drought stress. Our study identified potential biological pathways and drought-responsive proteins related to stress/defense responses and plant hormone metabolism under drought stress. Collectively, our results provide new insights for further improving drought tolerance in cotton and other crops.

中文翻译：

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基于串联质量标签（TMT）的定量蛋白质组学分析揭示了棉花（棉（Gossypium hirsutum L.））的细根对干旱胁迫的响应。

棉花（陆地棉）是全球最重要的经济作物之一。细根是根系的核心部分，有助于植物吸收水分和养分。但是，棉花细根对土壤干旱的响应机制尚不清楚。为了阐明干旱胁迫下棉株细根的蛋白质组学变化，分别对对照组（CK）和干旱胁迫（DS）组进行了70–75％和40–45％的土壤相对含水量处理。然后，使用串联质量标签（TMT）技术确定细根组织样品的蛋白质组谱。干旱显着降低了棉苗平均根直径，而总根长和抗氧化酶活性增加。为了进一步研究干旱响应的分子机制，分别在0、30和45 DAD（干旱胁迫后的天数）成对比较在CK和DS处理下组织之间的蛋白质组差异。在“ DS30与CK30”比较中，总共上调了118种差异表达蛋白（DEP），而下调了105种。在“ DS45与CK45”比较中，上调了662个DEP，下调了611个DEP。这些DEP的功能根据其途径进行分类。在早期干旱（30 DAD）下，一些涉及“促凝素，粉刺质和蜡质合成”途径的DEPs被上调，而被下调的DEPs主要在“单萜类生物合成”途径中富集。四十五天的土壤干旱对参与代谢的DEP有更大的影响。许多涉及“碳水化合物代谢”，“能量代谢”，“脂肪酸代谢”的蛋白质，“氨基酸代谢”和“二次代谢物的生物合成”被确定为DEP。此外，与离子转运，胁迫/防御和植物激素有关的蛋白质也被证明在确定干旱胁迫下棉花植株的细根生长中发挥作用。我们的研究确定了与干旱胁迫下胁迫/防御反应和植物激素代谢有关的潜在生物途径和干旱响应蛋白。总的来说，我们的结果为进一步提高棉花和其他农作物的耐旱性提供了新的见识。我们的研究确定了与干旱胁迫下胁迫/防御反应和植物激素代谢相关的潜在生物途径和干旱响应蛋白。总的来说，我们的结果为进一步提高棉花和其他农作物的耐旱性提供了新的见识。我们的研究确定了与干旱胁迫下胁迫/防御反应和植物激素代谢相关的潜在生物途径和干旱响应蛋白。总的来说，我们的结果为进一步提高棉花和其他农作物的耐旱性提供了新的见识。