Plants need tight regulation of photosynthetic electron transport for survival and growth under environ- mental and metabolic conditions. For this purpose, the linear electron transport （LET） pathway is supple- ment...Plants need tight regulation of photosynthetic electron transport for survival and growth under environ- mental and metabolic conditions. For this purpose, the linear electron transport （LET） pathway is supple- mented by a number of alternative electron transfer pathways and valves. In Arabidopsis, cyclic electron transport （CET） around photosystem I （PSI）, which recycles electrons from ferrodoxin to plastoquinone, is the most investigated alternative route. However, the interdependence of LET and CET and the relative importance of CET remain unclear, largely due to the difficulties in precise assessment of the contribution of CET in the presence of LET, which dominates electron flow under physiological conditions. We there- fore generated Arabidopsis mutants with a minimal water-splitting activity, and thus a low rate of LET, by combining knockout mutations in Psb01, PsbP2, PsbQ1, PsbQ2, and PsbR loci. The resulting 45 mutant is viable, although mature leaves contain only ~20% of wild-type naturally less abundant Psb02 protein. 45 plants compensate for the reduction in LET by increasing the rate of CET, and inducing a strong non-photochemical quenching （NPQ） response during dark-to-light transitions. To identify the molecular origin of such a high-capacity CET, we constructed three sextuple mutants lacking the qE component of NPQ （45 npq4-1）, NDH-mediated CET （45 crr4-3）, or PGR5-PGRLl-mediated CET （45 pgrS）. Their analysis revealed that PGR5-PGRLl-mediated CET plays a major role in ~pH formation and induction of NPQ in C3 plants. Moreover, while pgr5 dies at the seedling stage under fluctuating light conditions, 45 pgr5 plants are able to survive, which underlines the importance of PGR5 in modulating the intersystem electron transfer.展开更多
光是光合作用不可或缺的底物。然而过量的光照会对光合生物造成氧化胁迫和严重的损害。为了应对持续变化的光环境,蓝藻演化形成了灵活的电子传递网络。围绕光系统I(photosystem I,PSI)的循环电子传递(cyclic electron transport,CET)将...光是光合作用不可或缺的底物。然而过量的光照会对光合生物造成氧化胁迫和严重的损害。为了应对持续变化的光环境,蓝藻演化形成了灵活的电子传递网络。围绕光系统I(photosystem I,PSI)的循环电子传递(cyclic electron transport,CET)将电子从铁氧还蛋白Fd回流到质体醌(plastoquinone,PQ)库,产生ATP且不积累NADPH。在蓝藻和高等植物中发现了2种不同的CET途径,即NDH依赖途径和PGR5依赖途径。蓝藻中黄素二铁蛋白Flv1/Flv3参与了类梅勒(Mehler-like)反应,从PSI接受电子直接将氧气还原为水,且没有活性氧的形成。以集胞藻为试验材料,通过分析不同的CET和Flv突变株在不同光照条件下的生理特征以及其P700氧化/还原动力学,进而研究CET途径和类梅勒反应在集胞藻中的功能。结果表明NDH-1复合体对CET的贡献率超过90%,维持细胞能在持续高光环境下生长,而迅速应激的类梅勒反应在缓解瞬时高光胁迫时发挥了重要作用。因此我们认为在集胞藻中NDH-1介导的循环电子途径是稳固支持其适应高光逆境的主要机制,而类梅勒反应则是在现有主要途径严重不足时的1个备用途径。响应迅速的FLV路径是野生型和NDH-1突变株的补足。展开更多
文摘Plants need tight regulation of photosynthetic electron transport for survival and growth under environ- mental and metabolic conditions. For this purpose, the linear electron transport （LET） pathway is supple- mented by a number of alternative electron transfer pathways and valves. In Arabidopsis, cyclic electron transport （CET） around photosystem I （PSI）, which recycles electrons from ferrodoxin to plastoquinone, is the most investigated alternative route. However, the interdependence of LET and CET and the relative importance of CET remain unclear, largely due to the difficulties in precise assessment of the contribution of CET in the presence of LET, which dominates electron flow under physiological conditions. We there- fore generated Arabidopsis mutants with a minimal water-splitting activity, and thus a low rate of LET, by combining knockout mutations in Psb01, PsbP2, PsbQ1, PsbQ2, and PsbR loci. The resulting 45 mutant is viable, although mature leaves contain only ~20% of wild-type naturally less abundant Psb02 protein. 45 plants compensate for the reduction in LET by increasing the rate of CET, and inducing a strong non-photochemical quenching （NPQ） response during dark-to-light transitions. To identify the molecular origin of such a high-capacity CET, we constructed three sextuple mutants lacking the qE component of NPQ （45 npq4-1）, NDH-mediated CET （45 crr4-3）, or PGR5-PGRLl-mediated CET （45 pgrS）. Their analysis revealed that PGR5-PGRLl-mediated CET plays a major role in ~pH formation and induction of NPQ in C3 plants. Moreover, while pgr5 dies at the seedling stage under fluctuating light conditions, 45 pgr5 plants are able to survive, which underlines the importance of PGR5 in modulating the intersystem electron transfer.
基金Elite Youth Program of Chinese Academy of Agricultural Sciences and the Agricultural Science and Technology Innovation Program。
文摘光是光合作用不可或缺的底物。然而过量的光照会对光合生物造成氧化胁迫和严重的损害。为了应对持续变化的光环境,蓝藻演化形成了灵活的电子传递网络。围绕光系统I(photosystem I,PSI)的循环电子传递(cyclic electron transport,CET)将电子从铁氧还蛋白Fd回流到质体醌(plastoquinone,PQ)库,产生ATP且不积累NADPH。在蓝藻和高等植物中发现了2种不同的CET途径,即NDH依赖途径和PGR5依赖途径。蓝藻中黄素二铁蛋白Flv1/Flv3参与了类梅勒(Mehler-like)反应,从PSI接受电子直接将氧气还原为水,且没有活性氧的形成。以集胞藻为试验材料,通过分析不同的CET和Flv突变株在不同光照条件下的生理特征以及其P700氧化/还原动力学,进而研究CET途径和类梅勒反应在集胞藻中的功能。结果表明NDH-1复合体对CET的贡献率超过90%,维持细胞能在持续高光环境下生长,而迅速应激的类梅勒反应在缓解瞬时高光胁迫时发挥了重要作用。因此我们认为在集胞藻中NDH-1介导的循环电子途径是稳固支持其适应高光逆境的主要机制,而类梅勒反应则是在现有主要途径严重不足时的1个备用途径。响应迅速的FLV路径是野生型和NDH-1突变株的补足。
