Due to their sessile lifestyle, plants have evolved unique mechanisms to deal with environmental challenges. Under stress, plant lipids are important as alternative sources of carbon and energy when sugars or starch are limited. Here, we applied combined heat and darkness and extended darkness to a panel of ~ 300 Arabidopsis accessions to study lipid remodeling under carbon starvation. Natural allelic variation at 3-KETOACYL-COENZYME A SYNTHASE4 (KCS4), a gene encoding for an enzyme involved in very long chain fatty-acid (VLCFA) synthesis, underlies a differential accumulation of polyunsaturated triacylglycerols (puTAGs) under stress. Ectopic expression in yeast and plants proved that KCS4 is a functional enzyme localized in the ER with specificity for C22 and C24 saturated acyl-CoA. Allelic mutants and transient overexpression in planta revealed the differential role of KCS4 alleles in VLCFA synthesis and wax coverage, puTAG accumulation and biomass. Moreover, the region harboring KCS4 is under high selective pressure and allelic variation at KCS4 correlated with environmental parameters from the locales of Arabidopsis accessions. Our results provide evidence that KCS4 plays a decisive role in the subsequent fate of fatty acids released from chloroplast-membrane lipids under carbon starvation. This work sheds light on both plant response mechanisms and the evolutionary events shaping the lipidome under carbon starvation.

中文翻译：

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你好黑暗，我的老朋友：3-酮脂酰辅酶 A 合成酶 4 是拟南芥中甘油三酯合成调控的一个分支点

由于其固定的生活方式，植物已经进化出独特的机制来应对环境挑战。在压力下，当糖或淀粉有限时，植物脂质作为碳和能量的替代来源很重要。在这里，我们对一组约 300 份拟南芥种质应用了热暗结合和延长黑暗，以研究碳饥饿条件下的脂质重塑。3-KETOACYL-COENZYME A SYNTHASE4 (KCS4) 的天然等位基因变异是一种编码参与超长链脂肪酸 (VLCFA) 合成的酶的基因，是压力下多不饱和三酰甘油 (puTAG) 差异积累的基础。酵母和植物中的异位表达证明 KCS4 是一种定位于 ER 的功能酶，对 C22 和 C24 饱和酰基辅酶 A 具有特异性。植物中的等位基因突变体和瞬时过表达揭示了 KCS4 等位基因在 VLCFA 合成和蜡覆盖、puTAG 积累和生物量中的不同作用。此外，包含 KCS4 的区域处于高选择压力下，KCS4 的等位基因变异与拟南芥种质地点的环境参数相关。我们的结果提供的证据表明，KCS4 在碳饥饿条件下从叶绿体膜脂质释放的脂肪酸的后续命运中起着决定性作用。这项工作阐明了植物反应机制和碳饥饿条件下塑造脂质组的进化事件。包含 KCS4 的区域处于高选择压力下，并且 KCS4 的等位基因变异与来自拟南芥种质地点的环境参数相关。我们的结果提供的证据表明，KCS4 在碳饥饿条件下从叶绿体膜脂质释放的脂肪酸的后续命运中起着决定性作用。这项工作阐明了植物反应机制和碳饥饿条件下塑造脂质组的进化事件。包含 KCS4 的区域处于高选择压力下，并且 KCS4 的等位基因变异与来自拟南芥种质地点的环境参数相关。我们的结果提供的证据表明，KCS4 在碳饥饿条件下从叶绿体膜脂质释放的脂肪酸的后续命运中起着决定性作用。这项工作阐明了植物反应机制和碳饥饿条件下塑造脂质组的进化事件。