The role and signaling of sphingosine-l-phosphate （SIP） during darkness-induced stomatal closure were examined in Vicia faba. Darkness substantially raised S 1P and hydrogen peroxide （H202） levels and closed stoma...The role and signaling of sphingosine-l-phosphate （SIP） during darkness-induced stomatal closure were examined in Vicia faba. Darkness substantially raised S 1P and hydrogen peroxide （H202） levels and closed stomata. These darkness effects were significantly suppressed by DL-threo-dihydrosphingosine （DL-threo-DHS） and N,N-dimethylsphingosine （DMS）, two inhibi- tors of long-chain base kinases. Exogenous SIP led to stomatal closure and H202 production, and the effects of SIP were largely prevented by the H202 modulators ascorbic acid, catalase, and diphenyleneiodonium. These results indicated that SIP mediated darkness-induced stomatal closure by triggering H202 production. In addition, DL-threo-DHS and DMS significantly suppressed both darkness-induced cytosolic alkalization in guard cells and stomatal closure. Exogenous SIP caused cytosolic alkalization and stomatal closure, which could be largely abolished by butyric acid. These results demonstrated that SIP syn-thesis was necessary for cytosolic alkalization during stomatal closure caused by darkness. Furthermore, together with the data described above, inhibition of darkness-induced H202 production by butyric acid revealed that S 1P synthesis-induced cytosolic alkalization was a prerequisite for H202 production during stomatal closure caused by darkness, a conclusion supported by the facts that the pH increase caused by exogenous SIP had a shorter lag and peaked faster than H202 levels and that butyric acid prevented exogenous SIP-induced H202 production. Altogether, our data suggested that darkness induced SIP synthesis, causing cytosolic alkalization and subsequent H202 production, finally leading to stomatal closure.展开更多
It remains challenging to develop methods that can precisely control the self-assembling kinetics and thermodynamics of peptide hydrogelators to achieve hydrogels with optimal properties.Here we report the hydrogelati...It remains challenging to develop methods that can precisely control the self-assembling kinetics and thermodynamics of peptide hydrogelators to achieve hydrogels with optimal properties.Here we report the hydrogelation of peptide hydrogelators by an enzymatically induced pH switch,which involves the combination of glucose oxidase and catalase with D-glucose as the substrate,in which both the gelation kinetics and thermodynamics can be controlled by the concentrations of D-glucose.This novel hydrogelation method could result in hydrogels with higher mechanical stability and lower hydrogelation concentrations.We further illustrate the application of this hydrogelation method to differentiate different D-glucose levels.展开更多
基金supported by the Graduate Education Innovation Program Projects of Ministry of Education, China (Grant No. F-0922)
文摘The role and signaling of sphingosine-l-phosphate （SIP） during darkness-induced stomatal closure were examined in Vicia faba. Darkness substantially raised S 1P and hydrogen peroxide （H202） levels and closed stomata. These darkness effects were significantly suppressed by DL-threo-dihydrosphingosine （DL-threo-DHS） and N,N-dimethylsphingosine （DMS）, two inhibi- tors of long-chain base kinases. Exogenous SIP led to stomatal closure and H202 production, and the effects of SIP were largely prevented by the H202 modulators ascorbic acid, catalase, and diphenyleneiodonium. These results indicated that SIP mediated darkness-induced stomatal closure by triggering H202 production. In addition, DL-threo-DHS and DMS significantly suppressed both darkness-induced cytosolic alkalization in guard cells and stomatal closure. Exogenous SIP caused cytosolic alkalization and stomatal closure, which could be largely abolished by butyric acid. These results demonstrated that SIP syn-thesis was necessary for cytosolic alkalization during stomatal closure caused by darkness. Furthermore, together with the data described above, inhibition of darkness-induced H202 production by butyric acid revealed that S 1P synthesis-induced cytosolic alkalization was a prerequisite for H202 production during stomatal closure caused by darkness, a conclusion supported by the facts that the pH increase caused by exogenous SIP had a shorter lag and peaked faster than H202 levels and that butyric acid prevented exogenous SIP-induced H202 production. Altogether, our data suggested that darkness induced SIP synthesis, causing cytosolic alkalization and subsequent H202 production, finally leading to stomatal closure.
基金supported by the National Natural Science Foundation of China(Grant No.11304156)the Priority Academic Program Development of Jiangsu Higher Education,Jiangsu PhD Gathering Scheme,the Technology Foundation for Selected Overseas Chinese Scholar,and the Scientific Research Foundationfor the Returned Overseas Chinese Scholars,State Education Ministry,China
文摘It remains challenging to develop methods that can precisely control the self-assembling kinetics and thermodynamics of peptide hydrogelators to achieve hydrogels with optimal properties.Here we report the hydrogelation of peptide hydrogelators by an enzymatically induced pH switch,which involves the combination of glucose oxidase and catalase with D-glucose as the substrate,in which both the gelation kinetics and thermodynamics can be controlled by the concentrations of D-glucose.This novel hydrogelation method could result in hydrogels with higher mechanical stability and lower hydrogelation concentrations.We further illustrate the application of this hydrogelation method to differentiate different D-glucose levels.
