Department of Biology, Texas A&M University, College Station, Texas 77843.
Department of Biology, Texas A&M University, College Station, Texas 77843
Plant Cell. 2020 Jan;32(1):81-99. doi: 10.1105/tpc.19.00552. Epub 2019 Oct 18.
Many solanaceous plants secrete acylsugars, which are branched-chain and straight-chain fatty acids esterified to Glu or Suc. These compounds have important roles in plant defense and potential commercial applications. However, several acylsugar metabolic genes remain unidentified, and little is known about regulation of this pathway. Comparative transcriptomics between low- and high-acylsugar-producing accessions of revealed that expression levels of known and novel candidate genes (putatively encoding beta-ketoacyl-(acyl-carrier-protein) synthases, peroxisomal acyl-activating enzymes, ATP binding cassette (ABC) transporters, and central carbon metabolic proteins) were positively correlated with acylsugar accumulation, except two genes previously reported to be involved in acylglucose biosynthesis. Genes putatively encoding oxylipin metabolic proteins, subtilisin-like proteases, and other antimicrobial defense proteins were upregulated in low-acylsugar-producing accessions. Transcriptome analysis after biochemical inhibition of biosynthesis of branched-chain amino acids (precursors to branched-chain fatty acids) by imazapyr showed concentration-dependent downregulation of known and most acylsugar candidate genes, but not defense genes. Weighted gene correlation network analysis identified separate coexpressed gene networks for acylsugar metabolism (including six transcription factor genes and flavonoid metabolic genes) and plant defense (including genes putatively encoding NB-ARC and leucine-rich repeat sequences, protein kinases and defense signaling proteins, and previously mentioned defense proteins). Additionally, virus-induced gene silencing of two trichomes preferentially expressed candidate genes for straight-chain fatty acid biosynthesis confirmed their role in acylsugar metabolism.
许多茄科植物分泌酰基糖，这是支链和直链脂肪酸与 Glu 或 Suc 酯化的产物。这些化合物在植物防御中具有重要作用，并有潜在的商业应用价值。然而，一些酰基糖代谢基因仍然未知，而且对该途径的调控知之甚少。对低产和高产酰基糖的品系进行比较转录组学分析表明，已知和新的候选基因（推测编码β-酮酰基-（酰基载体蛋白）合成酶、过氧化物酶体酰基激活酶、ATP 结合盒（ABC）转运蛋白和中心碳代谢蛋白）的表达水平与酰基糖积累呈正相关，除了两个先前报道与酰葡萄糖生物合成有关的基因。在低产酰基糖的品系中，推测编码氧化脂代谢蛋白、枯草杆菌蛋白酶样蛋白酶和其他抗菌防御蛋白的基因上调。生化抑制支链氨基酸（支链脂肪酸的前体）合成后进行的转录组分析表明，已知和大多数酰基糖候选基因以及防御基因均呈浓度依赖性下调。加权基因相关性网络分析确定了酰基糖代谢（包括 6 个转录因子基因和类黄酮代谢基因）和植物防御（包括推测编码 NB-ARC 和富含亮氨酸重复序列、蛋白激酶和防御信号蛋白以及前面提到的防御蛋白的基因）的独立共表达基因网络。此外，两种毛状体优先表达的候选基因的病毒诱导基因沉默（用于直链脂肪酸生物合成）证实了它们在酰基糖代谢中的作用。
