RgTAA1-RgYUCCA6-IAA axis mediates hydrogen gas-induced adventitious root formation in Rehmannia glutinosa root cuttings

H 2 could induce AR formation in R. glutinosa root cuttings. • H 2 elevates auxin levels via upregulating RgTAA1 and RgYUCCA6 in R. glutinosa . • H 2 -induced R. glutinosa AR formation depends on auxin synthesis and polar transport. • H 2 modulates multiple rooting processes relying on auxin signalling. Adventitious root (AR) formation is critical for the vegetative propagation and yield of Rehmannia glutinosa , a valuable medicinal plant. However, the molecular mechanisms governing R. glutinosa AR formation have not been documented previously. Here, we provide the first evidence that RgTAA1-RgYUCCA6-IAA axis mediated the hydrogen gas (H 2 )-induced AR formation in R. glutinosa root explants. Phenotypic and transcriptomic analysis demonstrated that H 2 triggered R. glutinosa AR emergence, and auxin biosynthesis genes ( RgYUCCA6 ), transport gene ( RgPIN-LIKES ), and early auxin response genes ( RgSAUR71 ) might be the target gene for H 2 . Next, we found that R. glutinosa AR exhibited an increase in endogenous H 2 and auxin levels during AR formation, and exogenous H 2 increased auxin levels. However, the application of 1-naphthylphthalamic acid and L -kynurenine ( L -kyn) blocked the auxin accumulation and AR formation. Further, H 2 upregulated the expression of RgTAA1 and RgYUCCA6 , leading to increased accumulation of indole-3-pyruvic acid (IPA) and IAA, but these were suppressed by L -kyn application. Meanwhile, H 2 substantially promotes AR formation in R. glutinosa by triggering AR primordium development, remodeling cell wall components, regulating rooting-related enzyme activities, maintaining cell viability, and all these processes are strictly dependent on auxin biosynthesis and polar transport. This is the pioneering study documenting the H 2 -induced R. glutinosa AR formation, shedding new light on the improvement of its vegetative propagation efficiency, and deepening our understanding of gasotransmitter-phytohormone crosstalk in plants. Download: Download high-res image (151KB) Download: Download full-size image