The role and proteomic analysis of ethylene in hydrogen gas-induced adventitious rooting development in cucumber (L.) explants.

Abstract

Using cucumber (Cucumis sativus L.) explants, this study examined the interplay between hydrogen gas and ethylene during adventitious root formation. Hydrogen-rich water (HRW) and the ethylene-releasing agent ethephon each promoted rooting, with peak responses at 50% HRW and 0.5 µM ethephon, respectively. Application of ethylene biosynthesis inhibitor AVG or the ethylene signaling blocker AgNO3 partially suppressed H2-induced rooting, indicating that ethylene functions downstream of hydrogen signaling. Two-dimensional electrophoresis combined with mass spectrometry revealed distinct proteomic shifts: HRW altered 24 proteins (9 up, 15 down), ethephon altered 14 proteins (4 up, 10 down), and HRW+AVG altered 10 proteins (1 up, 9 down). Six proteins were highlighted for further analysis: photosynthesis-related Rubisco, SBPase, and OEE1; amino acid metabolism-related TDH; antioxidant enzyme CAPX; and protein-folding factor PDI. Real-time PCR data corroborated the proteomic findings at the mRNA level, supporting a model in which ethylene acts as a downstream signaling molecule in hydrogen-induced adventitious rooting.

Mechanism

Hydrogen gas promotes adventitious rooting by triggering ethylene as a downstream signaling molecule; this cascade modulates expression of photosynthesis-related proteins (Rubisco, SBPase, OEE1), amino acid metabolism enzyme TDH, antioxidant enzyme CAPX, and protein-folding factor PDI.