Gasotransmitter HS accelerates seed germination via activating AOX mediated cyanide-resistant respiration pathway.

Hydrogen sulfide (HS) has been witnessed as a crucial gasotransmitter involving in various physiological processes in plants. HS signaling has been reported to involve in regulating seed germination, but the underlying mechanism remains poorly understood. Here, we found that endogenous HS production was activated in germinating Arabidopsis seeds, correlating with upregulated both the transcription and the activity of L-cysteine desulfhydrase (EC 4.4.1.28, LCD and DES1) responsible for HS production. Moreover, seed germination could be significantly accelerated by exogenous NaHS (the HS donor) fumigation and over-expressing DES1, while HS-generation defective (lcd/des1) seeds exhibited decreased germination speed. We also confirmed that the alternative oxidase (AOX), a cyanide-insensitive terminal oxidase, can be stimulated by imbibition. Furthermore, exogenous HS fumigation and over-expressing DES1 could significantly reinforced imbibition induced increase of both the AOX1A expression and AOX protein abundance, while this increase could be obviously weakened in lcd/des1. Additionally, exogenous HS fumigation mediated post-translational modification to keep AOX in its reduced and active state, which might involve HS induced improvement of the reduced GSH content and the cell reducing power. The promotive effect of HS on germination was clearly impaired by inducing aox1a mutation, indicating that AOX acts downstream of HS signaling to accelerate seed germination. Consequently, HS signaling was activated during germination then acted as a trigger to induce AOX mediated cyanide-resistant respiration to accelerate seed germination. Our study correlates HS signaling to cyanide-resistant respiration, providing evidence for more extensive studies of HS signaling.