Promiscuous Artemisia annua glycosylphosphatidylinositol-anchored lipid transfer protein 1 (AaLTPG1) promotes terpenoids accumulation in planta

Abstract

LTPG, encoded by a glycosylphosphatidylinositol-anchored lipid transfer protein family gene, plays a role in exporting fatty acids to the plant surface through the hydrophilic cell wall layer. While soluble extracellular LTPs are known to function in terpenoid accumulation in trichomes, whether membrane-integrated LTPG influences terpenoid accumulation and its underlying mechanisms remains poorly understood. In this study, we report an Artemisia annua LTPG1, which is strongly expressed in floral tissues and positively correlated with three artemisinin biosynthetic genes. The recombinant AaLTPG1 displayed promiscuous binding activity with fatty acids and artemisinin precursors in vitro, resulting in an increase in terpenoids and lipids contents in both AaLTPG1 transgenic tobacco without altering trichome initiation, development, or secretion. Transcriptome sequencing further revealed that ethylene responsive genes were repressed in AaLTPG1-overexpressing tobacco plants. Consistently, artemisinin and its precursors were found to increase transiently in A. annua leaves, and the expression level of ethylene-responsive factors (ERFs) was down-regulated in A. annua. Collectively, this work illustrates the positive regulatory role of LTPG in terpenoids and lipids accumulation by exporting hydrophobic metabolites and repressing ethylene signaling, making AaLTPG1 a potential ideal target for metabolic engineering to improve artemisinin accumulation.