In plant chloroplasts, photosystem II (PSII) com-plexes, together with light-harvesting complex II (LHCII), form various PSII-LHCII supercomplexes (SCs). This process likely involves immunophilins, but the underlying regulatory mechanisms are unclear. Here, by comparing Arabidopsis thaliana mutants lacking the chloroplast lumen-localized immunophilin CYCLOPHILIN28 (CYP28) to wild-type and transgenic complemented lines, we de-termined that CYP28 regulates the assembly and accumulation of PSII-LHCII SCs. Compared to the wild type, cyp28 plants showed accelerated leaf growth, earlier flowering time, and enhanced accu-mulation of high molecular weight PSII-LHCII SCs under normal light conditions. The lack of CYP28 also significantly affected the electron transport rate. Blue native-polyacrylamide gel electrophoresis analysis revealed more Lhcb6 and less Lhcb4 in M-LHCII-Lhcb4-Lhcb6 complexes in cyp28 versus wild-type plants. Peptidyl-prolyl cis/trans isomerase (PPIase) activity assays revealed that CYP28 ex-hibits weak PPIase activity and that its K113 and E187 residues are critical for this activity. Mutant analysis suggested that CYP28 may regulate PSII-LHCII SC accumulation by altering the configuration of Lhcb6 via its PPIase activity. Furthermore, the Lhcb6-P139 residue is critical for PSII-LHCII SC assembly and accumulation. Therefore, our findings suggest that CYP28 likely regulates PSII-LHCII SC assembly and accumulation by altering the config-uration of P139 of Lhcb6 via its PPIase activity.

Chinese Education Ministry's Key Laboratory of Western Resources and Modern Biotechnology,Key Laboratory of Biotechnology Shaanxi Province,College of Life Sciences,Northwest University,Xi'an 710069,China

[1]Weining Zhu;Linqing Xu;Xiaoxia Yu;Ying Zhong-.The immunophilin CYCLOPHILIN28 affects PSII-LHCII supercomplex assembly and accumulation in Arabidopsis thaliana)[J].植物学报（英文版）,2022(04):915-929

immunophilin,CYCLOPHILIN28,LHCII,supercomplex,supercomplexes,immunophilins,CYP28,cyp28,Lhcb6,Lhcb4,Peptidyl,PPIase,K113,E187,P139

affects,PSII,assembly,accumulation,Arabidopsis,thaliana,In,chloroplasts,photosystem,together,light,harvesting,form,various,SCs,This,process,likely,involves,but,underlying,regulatory,mechanisms,unclear,Here,by,comparing,mutants,lacking,lumen,localized,wild,type,transgenic,complemented,lines,termined,that,regulates,Compared,plants,showed,accelerated,leaf,growth,earlier,flowering,enhanced,high,molecular,weight,normal,conditions,also,significantly,affected,electron,transport,Blue,native,polyacrylamide,gel,electrophoresis,analysis,revealed,less,versus,prolyl,cis,isomerase,activity,assays,hibits,weak,residues,critical,this,Mutant,suggested,may,altering,configuration,via,Furthermore,Therefore,our,findings

0.34781