Sabharwal Tanya, Sathasivan Kanagasabapathi, Mehdy Mona C
Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas, United States of America.
PLoS One. 2017 Jun 5;12(6):e0178761. doi: 10.1371/journal.pone.0178761. eCollection 2017.
Diatoms rapidly release extracellular oxylipins (oxygenated lipids) including polyunsaturated aldehydes in response to herbivory and other stresses. Oxylipins have several defense-related activities including inhibition of reproduction in herbivores and signaling to distant diatoms. Physiological changes in diatoms exposed to varying levels of oxylipins are only beginning to be understood. In this study, Phaeodactylum tricornutum cultures were treated with sublethal concentrations of the polyunsaturated aldehyde trans,trans-2,4-decadienal (DD) to assess effects on lipid composition and membrane permeability. In cells treated with DD for 3 hr, all measured saturated and unsaturated fatty acids significantly decreased (0.46-0.69 fold of levels in solvent control cells) except for 18:2 (decreased but not significantly). The decrease was greater in the polyunsaturated fatty acid pool than the saturated and monounsaturated fatty acid pool. Analysis of lipid classes revealed increased abundances of phosphatidylethanolamine and phosphatidylcholine at 3 and 6 hr. Concomitantly, these and other membrane lipids exhibited increased saturated and monounsaturated acyl chains content relative to polyunsaturated acyl chains compared to control cells. Evidence of decreased plasma membrane permeability in DD treated cells was obtained, based on reduced uptake of two of three dyes relative to control cells. Additionally, cells pre-conditioned with a sublethal DD dose for 3 hr then treated with a lethal DD dose for 2 hr exhibited greater membrane integrity than solvent pre-conditioned control cells that were similarly treated. Taken together, the data are supportive of the hypothesis that membrane remodeling induced by sublethal DD is a key element in the development of cellular resistance in diatoms to varying and potentially toxic levels of polyunsaturated aldehydes in environments impacted by herbivory or other stresses.
硅藻在受到食草动物啃食和其他胁迫时，会迅速释放细胞外氧化脂质（含氧脂质），包括多不饱和醛。氧化脂质具有多种与防御相关的活性，包括抑制食草动物的繁殖以及向远处的硅藻发出信号。暴露于不同水平氧化脂质的硅藻的生理变化才刚刚开始被了解。在本研究中，用亚致死浓度的多不饱和醛反式，反式-2,4-癸二烯醛（DD）处理三角褐指藻培养物，以评估其对脂质组成和膜通透性的影响。在用DD处理3小时的细胞中，除18:2（减少但不显著）外，所有测得的饱和脂肪酸和不饱和脂肪酸均显著降低（为溶剂对照细胞水平的0.46 - 0.69倍）。多不饱和脂肪酸池中的减少幅度大于饱和脂肪酸和单不饱和脂肪酸池。脂质类别分析显示，在3小时和6小时时，磷脂酰乙醇胺和磷脂酰胆碱的丰度增加。与此同时，与对照细胞相比，这些以及其他膜脂质的饱和和单不饱和酰基链含量相对于多不饱和酰基链有所增加。基于相对于对照细胞三种染料中两种染料摄取量的减少，获得了DD处理细胞中质膜通透性降低的证据。此外，用亚致死剂量的DD预处理3小时然后用致死剂量的DD处理2小时的细胞，比经过类似处理的溶剂预处理对照细胞表现出更高的膜完整性。综上所述，这些数据支持以下假设：亚致死剂量的DD诱导的膜重塑是硅藻在受食草动物啃食或其他胁迫影响的环境中，对不同水平且可能有毒的多不饱和醛产生细胞抗性的关键因素。
