hrvatski

TROL-FNR interakcija utječe na raspodjelu fotosintetskih elektrona prema daljnjim putevima prijenosa energije

Završni korak u fotosintetskom prijenosu elektrona s feredoksina na NADP+ katalizira feredoksin:NADP+ oksidoreduktaza (FNR). On je prihvačen na tilakoidne membrane pomoću integralnog membranskog proteina TROL (thylakoid rhodanese-like). Metodom elektronske paramagnetske rezonance (EPR) detektirali smo i kvantificirali stvaranje slobodnih radikala u kloroplastima vrste A. thaliana kojima nedostaje TROL (trol), da bismo otkrili što se dešava s elektronima nizvodno od fotosustava I. Za praćenje superoksidnog aniona (O2.-) koristili smo DMPO, dok je za detekciju ostalih slobodnih radikala korišten Tiron. Biljke su uzgajane u različitim uvjetima osvjetljenja i mjerene na svjetlu i u mraku. U trol biljkama je primjećeno smanjeno nakupljanje O2.- , dok je nakupljanje ostalih radikala kisika bilo pojačano u svim testiranim uvjetima, osim kod biljaka prilagođenih na jako osvjetljenje. Osim toga, formiranje O2.- potaknuto dodatkom metil viologena (MV) bilo je smanjeno u trol tilakoidima, što upućuje na mogućnost da FNR otpušten s TROL-a ima izraženu aktivnost uklanjaja elektrona kojom može nadjačati i MV. Mjerenjem aktivnosti nekoliko enzima uključenih u detoksifikaciju reaktivnih molekula kisika utvrdili smo da je TROL-FNR kompleks uključen u odgovor na stres. Na temelju dobivenih rezultata predlažemo novi mehanizam fotosintetske regulacije u kojem dinamično vezanje ili otpuštanje FNR-a s TROL-a određuje kojim će daljnjim putevime prijenosa energije elektroni biti raspodijeljeni. The last step of photosynthetic electron transfer from ferredoxin to NADP+ is catalyzed by the ferredoxin:NADP+ oxidoreductase (FNR). This enzyme is recruited to thylakoid membranes via the integral membrane protein TROL (thylakoid rhodanese-like). We used electron paramagnetic resonance (EPR) for detection and quantification of free radical formation and electron partitioning in TROL-depleted (trol) Arabidopsis chloroplasts, to clarify the fate of electrons downstream of PSI. DMPO was used to quantify the superoxide anione (O2.- ) formation, while the propagation of other free radicals was monitored by Tiron. Plants were grown under different light regimes and measured in both dark and light conditions. The accumulation of O2.- was reduced in trol plants, while the propagation of other oxygen radicals was elevated in all tested conditions, except for high-light adapted plants. Strikingly, methyl viologen-induced (MV) O2.- formation was diminished in trol thylakoids, suggesting that TROL-released FNR might have a pronounced scavenging activity which is even able to outcompete the MV-mediated O2.- production. By measuring activities of several ROS detoxifying enzymes in trol plants we demonstrated that the TROL-FNR branching point is integrated into plant stress responses. We suggest a novel mechanism of photosynthesis regulation in which dynamic binding and release of FNR from TROL might regulate electron partitioning between electron-conserving and -dissipating pathways.

TROL-FNR interakcija; EPR; slobodni kisikovi radikali; superoksidni anion; preraspodijela elektrona

nije evidentirano

engleski

TROL-FNR interaction influences the assignment of photosynthetically derived electrons to different energy transfer pathways

Završni korak u fotosintetskom prijenosu elektrona s feredoksina na NADP+ katalizira feredoksin:NADP+ oksidoreduktaza (FNR). On je prihvačen na tilakoidne membrane pomoću integralnog membranskog proteina TROL (thylakoid rhodanese-like). Metodom elektronske paramagnetske rezonance (EPR) detektirali smo i kvantificirali stvaranje slobodnih radikala u kloroplastima vrste A. thaliana kojima nedostaje TROL (trol), da bismo otkrili što se dešava s elektronima nizvodno od fotosustava I. Za praćenje superoksidnog aniona (O2.-) koristili smo DMPO, dok je za detekciju ostalih slobodnih radikala korišten Tiron. Biljke su uzgajane u različitim uvjetima osvjetljenja i mjerene na svjetlu i u mraku. U trol biljkama je primjećeno smanjeno nakupljanje O2.- , dok je nakupljanje ostalih radikala kisika bilo pojačano u svim testiranim uvjetima, osim kod biljaka prilagođenih na jako osvjetljenje. Osim toga, formiranje O2.- potaknuto dodatkom metil viologena (MV) bilo je smanjeno u trol tilakoidima, što upućuje na mogućnost da FNR otpušten s TROL-a ima izraženu aktivnost uklanjaja elektrona kojom može nadjačati i MV. Mjerenjem aktivnosti nekoliko enzima uključenih u detoksifikaciju reaktivnih molekula kisika utvrdili smo da je TROL-FNR kompleks uključen u odgovor na stres. Na temelju dobivenih rezultata predlažemo novi mehanizam fotosintetske regulacije u kojem dinamično vezanje ili otpuštanje FNR-a s TROL-a određuje kojim će daljnjim putevime prijenosa energije elektroni biti raspodijeljeni. The last step of photosynthetic electron transfer from ferredoxin to NADP+ is catalyzed by the ferredoxin:NADP+ oxidoreductase (FNR). This enzyme is recruited to thylakoid membranes via the integral membrane protein TROL (thylakoid rhodanese-like). We used electron paramagnetic resonance (EPR) for detection and quantification of free radical formation and electron partitioning in TROL-depleted (trol) Arabidopsis chloroplasts, to clarify the fate of electrons downstream of PSI. DMPO was used to quantify the superoxide anione (O2.- ) formation, while the propagation of other free radicals was monitored by Tiron. Plants were grown under different light regimes and measured in both dark and light conditions. The accumulation of O2.- was reduced in trol plants, while the propagation of other oxygen radicals was elevated in all tested conditions, except for high-light adapted plants. Strikingly, methyl viologen-induced (MV) O2.- formation was diminished in trol thylakoids, suggesting that TROL-released FNR might have a pronounced scavenging activity which is even able to outcompete the MV-mediated O2.- production. By measuring activities of several ROS detoxifying enzymes in trol plants we demonstrated that the TROL-FNR branching point is integrated into plant stress responses. We suggest a novel mechanism of photosynthesis regulation in which dynamic binding and release of FNR from TROL might regulate electron partitioning between electron-conserving and -dissipating pathways.

TROL-FNR interaction; EPR; ROS; superoxide anion; electron partitioning

nije evidentirano