LoWRKY1 Alleviates PEG-Induced Membrane and Enhances Antioxidant Responses Damage in Larix olgensis and Tobacco

Abstract

Drought stress constitutes a persistent constraint on tree survival, and larch, owing to their distinctive needle morphology, deploys drought-responsive strategies that differ from those of broad-leaved trees. In this study, we identified a putative transcription factor, LoWRKY1, that is highly expressed in larch needles and induced by both polyethylene glycol (PEG)-mediated osmotic stress and abscisic acid (ABA) treatment. Heterologous overexpression of LoWRKY1 in tobacco enhanced leaf relative water content (RWC), reduced ion leakage (IL) and malondialdehyde (MDA) levels, thereby mitigating damage to the membrane system. Furthermore, LoWRKY1 was shown to promote superoxide dismutase (SOD) and catalase (CAT) activities in both tobacco and Larix olgensis embryonic callus cells, effectively scavenging reactive oxygen species (ROS) and improving drought tolerance. Collectively, these findings establish that LoWRKY1 plays a positive role in PEG-induced osmotic stress responses in L. olgensis, providing a promising candidate gene for the genetic improvement in the drought tolerance in coniferous trees. More broadly, this work highlights the value of integrating heterologous expression with conifer embryonic callus systems to dissect stress-regulatory networks in conifers, thereby offering a practical strategy to accelerate functional genomics in tree species that remain recalcitrant to stable transformation.