NIR Fluorescent Probe for In Situ Bioimaging of Endogenous H₂S in Rice Roots under Al³⁺ and Flooding Stresses

Hydrogen sulfide (H₂S) is one of the typical reactive sulfur species, which exhibits an important role in regulating both physiological and pathological processes. Recent studies indicate that H₂S also serves as a key signaling molecule in a broad range of regulatory processes in plants. However, in situ imaging and detection of the levels of H₂S in plant tissues remains a challenge. In this work, a NIR fluorescent probe (HBTP-HS) was synthesized to achieve H₂S imaging in living plant tissues. HBTP-HS exhibited high sensitivity toward H₂S with a large Stokes shift (250 nm). HBTP-HS could be applied to HeLa cells to detect the fluctuation of endogenous H₂S levels in response to physiological stimulations. Importantly, HBTP-HS was utilized for direct H₂S imaging of rice roots and revealed the upregulation of H₂S signaling in response to aluminum ions and flooding stresses. Our work thus provides a new tool to investigate H₂S-involved signal interaction and protective resistance of crops under environmental stresses.