Roles of an Auxin Transport Inhibitor and Methyl Jasmonate in Waterlogging-Induced Aerenchyma Formation in Luffa

Waterlogging stress is a major abiotic stressor that severely constrains crop growth and productivity. Aerenchyma provides intercellular air spaces to transport oxygen to the root, which is essential for survival under waterlogged conditions. However, the mechanism underlying the response to waterlogging and aerenchyma formation in luffa remains poorly understood. In this study, we identified distinct phenotypic responses between two cultivars: ‘Zhonglü’ exhibited aerenchyma formation in the hypocotyl under waterlogging, whereas ‘Yalü’ did not. Transcriptome profiling of ‘Zhonglü’ revealed differentially expressed genes linked to plant hormone signal transduction, including fifteen auxin-related and two jasmonate-related genes, which may be involved in waterlogging-induced aerenchyma formation and are proposed as candidate regulators. Furthermore, exogenous application of 5 μmol/L N-1-naphthylphthalamic acid (NPA) and 20 μmol/L methyl jasmonate (MeJA) significantly enhanced aerenchyma formation. Notably, these treatments uncovered a regulatory node wherein NPA-disrupted auxin transport and jasmonate signaling converge to coordinately fine-tune the expression of ARF18, IAA32, GH3.17 and TIFY9 genes in the hypocotyl. Taken together, this study definitely advances our knowledge of the morphological and transcriptomic responses of Luffa under waterlogging stress and sheds new lights on its adaptive mechanisms.