[Effects of melatonin on photosynthetic properties and osmoregulatory substance contents of cucumber seedlings under salt-alkali stress]. / è¤ªé»‘ç´ å¯¹ç›ç¢±å¤åˆèƒè¿«ä¸‹é»„ç“œå¹¼è‹—å ‰åˆç‰¹æ€§å’Œæ¸—é€è°ƒèŠ‚ç‰©è´¨å«é‡çš„å½±å“.

To determine the mitigating effects of exogenous melatonin on salt-alkali stress in cucumber, we mea-sured photosynthetic characteristics and osmoregulatory substance content of cucumber leaves under salt-alkali stress, using 'Xinchun 4' cucumber as the test material and a salt-alkali complex (NaCl:Na2SO4:Na2CO3:NaHCO3 = 1:9:1:9) to simulate stress. The results showed that compared with the normal seedlings, the exogenous application of 10 µmol·L-1 melatonin significantly increased the contents of chlorophyll, soluble sugar, and soluble protein, as well as net photosynthetic rate, stomatal conductance, transpiration rate, photosystem Ⅱ maximum photochemical efficiency, actual photochemical efficiency, apparent photosynthetic electron transfer rate, and photochemical burst coefficient of cucumber seedlings under 40 mmol·L-1 salt-alkali stress, but decreased intercellular CO2 concentration, non-photochemical burst coefficient, and sucrose, fructose, starch, and proline contents by 11.1%, 13.8%, 12.7%, 27.5%, 1.3% and 32.8%, respectively. Moreover, the activities of key enzymes for carbon assimilation (including ribulose-1,5-bisphosphate carboxylase/oxygenase and fructose-1,6-bisphosphate esterase) were significantly increased, whereas the mRNA expression levels of Rubisco subunits (CsrbcS and CsrbcL), CsFBA, CsRCA, CsFBPase and CsTK were downregulated. In conclusion, exogenous melatonin could increase the contents of chlorophyll and osmoregulatory substance, photosynthetic chemical efficiency, and key carbon assimilation enzyme activities of cucumber seedlings under salt-alkali stress, thereby enhance photosynthetic capacity and reduce the stress-induced plant damage. The results would provide theoretical basis for anti-saline plant cultivation.

Irisin protects against neuronal injury induced by oxygen-glucose deprivation in part depends on the inhibition of ROS-NLRP3 inflammatory signaling pathway.

Recent studies found that irisin, a newly discovered skeletal muscle-derived myokine during exercise, is also synthesized in various tissues of different species and protects against neuronal injury in cerebral ischemia. The NOD-like receptor pyrin 3 (NLRP3) inflammasome play an important role in detecting cellular damage and mediating inflammatory responses to aseptic tissue injury during ischemic stroke. However, it is unclear whether irisin is involved in the regulation of NLRP3 inflammasome activation during ischemic stroke. In the present study, PC12 neuronal cells were exposed to oxygen-glucose deprivation (OGD), exogenous irisin (12.5, 25, 50nmol/L) or NLRP3 inhibitor glyburide (50, 100, 200µmol/L) were used as an intervention reagent, NLRP3 was over-expressed or suppressed by transfection with a NLRP3 expressing vector or NLRP3-specifc siRNA, respectively. Our data showed that both irisin and its precursor protein fibronectin type III domain containing 5 (FNDC5) expression were significantly down-regulated (p<0.05); but oxidative stress and ROS-NLRP3 inflammasome signaling were activated by OGD (p<0.05); treatment with irisin or inhibition of NLRP3 reversed OGD-induced oxidative stress and inflammation (p<0.05). However, these irisin-mediated effects were blunted by over-expression NLRP3 (p<0.05). Taken together, our results firstly revealed that irisin mitigated OGD-induced neuronal injury in part via inhibiting ROS-NLRP3 inflammatory signaling pathway, suggesting a likely mechanism for irisin-induced therapeutic effect in ischemic stroke.

[Effects of exogenous salicylic acid and brassinolide on photosynthesis of cucumber seedlings under low temperature stress.] / æ°´æ¨é ¸å’Œæ²¹èœç´ å† é ¯å¯¹ä½Žæ¸©èƒè¿«ä¸‹é»„ç“œå¹¼è‹—å ‰åˆä½œç”¨çš„å½±å“.

An experiment was conducted to investigate the mechanism of the regulation of salicylic acid (SA) and 2,4-epibrassionolide (EBR) on photosynthesis in cucumber (Cucumis sativa) seedlings under low temperature stress. Taking cucumber cultivar 'Youbo1-5' as material, the seedlings were pre-treated with 1 mmol·L-1 SA or 0.1 µmol·L-1EBR (sprayed once a day), and then were exposed to chilling temperature (10 ℃/5 ℃, PFD 80 µmol·m-2·s-1) after being pre-treated 2 days. The results showed that the growth and net photosynthetic rate (Pn) of cucumber seedlings were decreased under low temperature stress. However, the Pn, maximal photochemical efficiency of PS2 (Fv/Fm), actual photochemical efficiency of PS2 (ΦPS2) and photochemical quenching coefficient (qP) were significantly improved in SA- and EBR-pretreated seedlings, and the increase range of non-photochemical quenching coefficient (NPQ) was decreased. Moreover, the activities of ribulose 1,5-biphosphate carboxylase/oxygenase (Rubisco), sedoheptulose-1,7-bisphosphatase (SBPase), fructose-1,6-bisphosphate aldolase (FBA) and transketolase (TK) were signi-ficantly increased. These findings suggested that SA and EBR improved photosynthesis of cucumber seedlings by promoting the activities of key enzymes and increased low temperature tolerance.