Drought stress is one of the major environmental factors that limited crop’s growth and production. Cassava known as a tropical crop that is widely distributed in Sub-Saharan Africa. It has a strong drought tolerance and can grow well under tough environmental conditions. Therefore, understanding how cassava responds to drought stress and coordinates survival and accumulation has great theoretical significance for improving crop drought resistance breeding. Many studies on cassava drought responses mainly focused on the leaf and whole seedling. Nevertheless, how the vasculature plays an important role in plant response to water deficiency remains to be fully elucidated. Here, comparative transcriptome analysis was performed on isolated mesophyll tissue and leaf vein vascular tissue of cassava variety KU50 after mild drought treatment to determine the molecular mechanism behind drought resistance in cassava vasculature. Our results showed that KU50 leaves had increased leaf temperature, with characters of rapidly decreased net photosynthetic rate, stomatal conductance, and transpiration rate in leaves, and the intercellular CO₂ concentration accumulated under drought stress. Comparative transcriptome profiling revealed that under drought stress, leaf mesophyll tissue mainly stimulated the biosynthesis of amino acids, glutamic acid metabolism, and starch and sucrose metabolism. In particular, the arginine biosynthesis pathway was significantly enhanced to adapt to the water deficiency in leaf mesophyll tissue. However, in vascular tissue, the response to drought mainly involved ion transmembrane transport, hormone signal transduction, and depolymerization of proteasome. Concretely, ABA signaling and proteasome metabolism, which are involved in ubiquitin regulation, were changed under drought stress in KU50 leaf vascular tissue. Our work highlights that the leaf vasculature and mesophyll in cassava have completely different drought response mechanisms.

干旱胁迫是限制作物生长和生产的主要环境因素之一。木薯被称为热带作物，广泛分布在撒哈拉以南非洲。它具有很强的耐旱性，在恶劣的环境条件下也能很好地生长。因此，了解木薯如何响应干旱胁迫，协调生存和积累，对于提高作物抗旱育种具有重要的理论意义。许多关于木薯干旱反应的研究主要集中在叶片和整株幼苗上。然而，脉管系统如何在植物对缺水的反应中发挥重要作用仍有待充分阐明。这里，对轻度干旱处理后木薯品种 KU50 的分离叶肉组织和叶脉维管组织进行比较转录组分析，以确定木薯维管系统抗旱的分子机制。结果表明，KU50叶片叶温升高，叶片净光合速率、气孔导度和蒸腾速率迅速下降，细胞间CO₂干旱胁迫下积累的浓度。比较转录组分析表明，在干旱胁迫下，叶肉组织主要刺激氨基酸的生物合成、谷氨酸代谢以及淀粉和蔗糖代谢。特别是精氨酸生物合成途径显着增强以适应叶肉组织缺水。然而，在维管组织中，对干旱的反应主要涉及离子跨膜转运、激素信号转导和蛋白酶体解聚。具体而言，在干旱胁迫下，KU50 叶维管组织中参与泛素调节的 ABA 信号传导和蛋白酶体代谢发生了变化。我们的工作强调，木薯的叶脉管系统和叶肉具有完全不同的干旱响应机制。