Earth and Biological Sciences Directorate, Pacific Northwest National Laboratories, 902 Battelle Blvd, Richland, WA 99301, USA.
Plant Biology Graduate Program, The Pennsylvania State University, University Park, PA 16802, USA.
Int J Mol Sci. 2020 Jun 23;21(12):4461. doi: 10.3390/ijms21124461.
Drought is the leading cause of agricultural yield loss among all abiotic stresses, and the link between water deficit and phloem protein contents is relatively unexplored. Here we collected phloem exudates from leaves during periods of drought stress and recovery. Our analysis identified 2558 proteins, the most abundant of which were previously localized to the phloem. Independent of drought, enrichment analysis of the total phloem exudate protein profiles from all samples suggests that the protein content of phloem sap is complex, and includes proteins that function in chaperone systems, branched-chain amino acid synthesis, trehalose metabolism, and RNA silencing. We observed 169 proteins whose abundance changed significantly within the phloem sap, either during drought or recovery. Proteins that became significantly more abundant during drought include members of lipid metabolism, chaperone-mediated protein folding, carboxylic acid metabolism, abscisic acid signaling, cytokinin biosynthesis, and amino acid metabolism. Conversely, proteins involved in lipid signaling, sphingolipid metabolism, cell wall organization, carbohydrate metabolism, and a mitogen-activated protein kinase are decreased during drought. Our experiment has achieved an in-depth profiling of phloem sap protein contents during drought stress and recovery that supports previous findings and provides new evidence that multiple biological processes are involved in drought adaptation.
干旱是所有非生物胁迫中导致农业产量损失的主要原因，而水分亏缺与韧皮部蛋白含量之间的联系还相对未知。在这里，我们在干旱胁迫和恢复期间收集了叶片的韧皮部渗出液。我们的分析鉴定了 2558 种蛋白质，其中最丰富的蛋白质以前定位于韧皮部。独立于干旱，对所有样本的总韧皮部渗出物蛋白图谱的富集分析表明，韧皮部汁液的蛋白质含量复杂，包括在伴侣系统、支链氨基酸合成、海藻糖代谢和 RNA 沉默中起作用的蛋白质。我们观察到 169 种蛋白质在韧皮部汁液中的丰度在干旱或恢复期间发生了显著变化。在干旱过程中丰度显著增加的蛋白质包括脂质代谢、伴侣介导的蛋白质折叠、羧酸代谢、脱落酸信号转导、细胞分裂素生物合成和氨基酸代谢的成员。相反，参与脂质信号转导、鞘脂代谢、细胞壁组织、碳水化合物代谢和丝裂原激活蛋白激酶的蛋白质在干旱期间减少。我们的实验对干旱胁迫和恢复期间韧皮部汁液蛋白含量进行了深入分析，支持了先前的发现，并提供了新的证据，表明多个生物学过程参与了干旱适应。
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