A chloroplast-targeted DnaJ protein contributes to maintenance of photosystem II under chilling stress.
DnaJ proteins act as essential molecular chaperones in protein homeostasis and protein complex stabilization under stress conditions. The roles of a tomato (Lycopersicon esculentum) chloroplast-targeted DnaJ protein (LeCDJ1), whose expression was upregulated by treatment at 4 and 42 °C, and with high light, NaCl, polyethylene glycol, and H2O2, were investigated here using sense and antisense transgenic tomatoes. The sense plants exhibited not only higher chlorophyll content, fresh weight and net photosynthetic rate, but also lower accumulation of reactive oxygen species and membrane damage under chilling stress. Moreover, the maximal photochemistry efficiency of photosystem II (PSII) (F v/F m) and D1 protein content were higher in the sense plants and lower in the antisense plants, and the photoinhibitory quenching was lower in the sense plants and higher in the antisense plants, suggesting that the inhibition of PSII was less severe in the sense plants and more severe in the antisense plants compared with the wild type. Furthermore, the PSII protein complexes were also more stable in the sense plants. Interestingly, the sense plants treated with streptomycin (SM), an inhibitor of organellar translation, still showed higher F v/F m, D1 protein content and PSII stability than the SM-untreated antisense plants. This finding suggested that the protective effect of LeCDJ1 on PSII was, at least partially, independent of D1 protein synthesis. Furthermore, chloroplast heat-shock protein 70 was identified as the partner of LeCDJ1. These results indicate that LeCDJ1 has essential functions in maintaining PSII under chilling stress.
College of Life Science, State Key Laboratory of Crop Biology, Shandong Agricultural University, Tai'an, Shandong 271018, PR China.
Fanying
F
Kong
Yongsheng
Y
Deng
Bin
B
Zhou
Guodong
G
Wang
Yu
Y
Wang
Qingwei
Q
Meng
D001483:Base Sequence; D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism; D003080:Cold Temperature; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D050956:HSP40 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D008027:Light; D018551:Solanum lycopersicum / Q000166:cytology / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D008969:Molecular Sequence Data; D045332:Photosystem II Protein Complex / Q000378:metabolism; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D017434:Protein Structure, Tertiary; D017382:Reactive Oxygen Species / Q000378:metabolism; D036226:Seedlings / Q000166:cytology / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D017422:Sequence Analysis, DNA; D013312:Stress, Physiological
D050956:HSP40 Heat-Shock Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D002734:Chlorophyll
Chilling stress; D1 protein; DnaJ protein; Hsp70; photosystem II; tomato.