Exogenous calcium alleviates photoinhibition of PSII by improving the xanthophyll cycle in peanut (Arachis hypogaea) leaves during heat stress under high irradiance.
Peanut is one of the calciphilous plants. Calcium (Ca) serves as a ubiquitous central hub in a large number of signaling pathways. The effect of exogenous calcium nitrate [Ca(NO3)2] (6 mM) on the dissipation of excess excitation energy in the photosystem II (PSII) antenna, especially on the level of D1 protein and the xanthophyll cycle in peanut plants under heat (40°C) and high irradiance (HI) (1 200 µmol m(-2) s(-1)) stress were investigated. Compared with the control plants [cultivated in 0 mM Ca(NO3)2 medium], the maximal photochemical efficiency of PSII (Fv/Fm) in Ca(2+)-treated plants showed a slighter decrease after 5 h of stress, accompanied by higher non-photochemical quenching (NPQ), higher expression of antioxidative genes and less reactive oxygen species (ROS) accumulation. Meanwhile, higher content of D1 protein and higher ratio of (A+Z)/(V+A+Z) were also detected in Ca(2+)-treated plants under such stress. These results showed that Ca(2+) could help protect the peanut photosynthetic system from severe photoinhibition under heat and HI stress by accelerating the repair of D1 protein and improving the de-epoxidation ratio of the xanthophyll cycle. Furthermore, EGTA (a chelant of Ca ion), LaCl3 (a blocker of Ca(2+) channel in cytoplasmic membrane), and CPZ [a calmodulin (CaM) antagonist] were used to analyze the effects of Ca(2+)/CaM on the variation of (A+Z)/(V+A+Z) (%) and the expression of violaxanthin de-epoxidase (VDE). The results indicated that CaM, an important component of the Ca(2+) signal transduction pathway, mediated the expression of the VDE gene in the presence of Ca to improve the xanthophyll cycle.
High-Tech Research Center of Shandong Academy of Agricultural Sciences, Ji'nan, China.
Sha
S
Yang
Fang
F
Wang
Feng
F
Guo
Jing-Jing
JJ
Meng
Xin-Guo
XG
Li
Shu-Ting
ST
Dong
Shu-Bo
SB
Wan
D000222:Adaptation, Physiological; D010367:Arachis / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D002147:Calmodulin / Q000378:metabolism; D018869:Heat-Shock Response; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D059748:Proteolysis; D017382:Reactive Oxygen Species / Q000378:metabolism; D036226:Seedlings / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D024341:Xanthophylls / Q000378:metabolism*
D002147:Calmodulin; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D024341:Xanthophylls; D002118:Calcium