[Hydrogen sulfide acted as a downstream signal was involved in the regulation of salicylic acid on photosynthesis of cucumber seedlings under low temperature and low light intensity]. / H2S作为下游信号参与SAå¯¹ä½Žæ¸©å¼±å ‰ä¸‹é»„ç“œå¹¼è‹—å ‰åˆä½œç”¨çš„è°ƒæŽ§.

Both salicylic acid (SA) and hydrogen sulfide (H2S) play an important role in regulating plant growth and development and physiological metabolism under abiotic stresses. As signal molecules, the interaction between them in regulating cucumber photosynthesis under low temperature and low light is still unclear. Here, we examined the regulation and interaction of SA and H2S on photosynthesis in cucumber seedlings under low temperature (8 ℃/5 ℃, day/night) and low light (100 µmol·m-2·s-1). Seedlings were foliar-sprayed with SA, sodium sulfide (NaHS, H2S donor), and their scavenger or biosynthesis inhibitors, respectively. Seedlings treated with deionized water at suitable temperature and light condition were used as the control. The results showed that SA increased the L-/D-cysteine desulfhydrase (LCD, DCD) activities and relative mRNA expression, and consequently promoted the endogenous H2S production. However, NaHS did not affect the activities and gene expressions of phenylalnine ammonialyase and isochorismate and endogenous SA level. Compared with the H2O-treated seedlings under low temperature and low light, SA- and NaHS-treated seedlings showed an increase in the photosynthetic rate, stomatal conductance and transpiration rate, while a decrease in intercellular CO2 concentration. SA and NaHS increased the CO2 assimilation, which mainly attributed to the increases in the activities of the ribulose-1, 5-bisphosphate carboxylase, rubisco activase, sedoheptulose-1, 7-bisphosphatase and fructose-1, 6-bisphosphatase, as well as their mRNA expression. Meanwhile, SA and NaHS improved the actual photochemical efficiency and maximal photochemical efficiency of PSII, and therefore alleviated the damage in photosynthetic apparatus and negative effect on growth from low temperature and low light stress. The SA-induced higher photosynthesis and growth in stressed seedlings were suppressed by addition of H2S scavenger hypotaurine. However, the H2S-induced tolerance of photosynthetic apparatus to low temperature and low light was not affected by SA biosynthesis inhibitor paclobutrazol and 2-aminoindan-2-phosphonic acid. Our results suggested that H2S, as a downstream signal of SA, was involved in regulating photosynthesis in cucumber seedlings under low temperature and low light.

Hydrogen sulfide is required for salicylic acid-induced chilling tolerance of cucumber seedlings.

Salicylic acid (SA) and hydrogen sulfide (H2S) have been proved to be multifunctional signal molecules to participate in the response of plants to abiotic stresses. However, it is still unclear whether there is interaction between SA and H2S in response to chilling intensity of cucumber seedlings. Here, we found SA was sensitive to chilling intensity. Under normal condition, NaHS (H2S donor) or removing endogenous H2S with hypotaurine (HT, a specific scavenger of H2S) and DL-propargylglycine (PAG, a specific inhibitor of H2S) has no effect on endogenous SA level; however, SA induced endogenous H2S content and activated the activities and mRNA level of L-/D-cysteine desulfhydrase (L-/D-CD), and inhibiting endogenous SA with paclobutrazol (PAC) or 2-aminoindan-2-phosphonic acid (AIP) blocked this effect, implying H2S may play a role after SA signal. Further studies showed that both SA and NaHS notably alleviated chilling injury, which was evidenced by lower electrolyte leakage (EL), MDA content, and ROS accumulation, compared with H2O treatment. Of note, SA and H2S improved the activities and mRNA level of antioxidant enzymes (SOD, POD, CAT, APX, and GR) as well as the contents of AsA and GSH. Additionally, the chilling-response genes (ICE, CBF1, and COR) were obviously upregulated by exogenous SA and NaHS. However, the positive effect of SA on chilling tolerance was inhibited by HT, whereas PAC or AIP did not affect NaHS-induced chilling tolerance. Taken together, the data reveals that H2S acts as a downstream signal of SA-induced chilling tolerance of cucumber via modulating antioxidant system and chilling-response genes.