Calcium affecting protein expression in longan under simulated acid rain stress
2015
Pan, Tengfei | Li, Yongyu | Ma, Cuilan | Qiu, Dongliang
Longan (Dimocarpus longana Lour. cv. Wulongling) of uniform one-aged seedlings grown in pots were selected to study specific proteins expressed in leaves under simulated acid rain (SiAR) stress and exogenous Ca²⁺ regulation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) results showed that there was a protein band specifically expressed under SiAR of pH 2.5 stress for 15 days with its molecular weight of about 23 kD. A 17 kD protein band specifically expressed after SiAR stress 5 days. Compared with pH 2.5, the pH 3.5 of SiAR made a less influence to protein expression. Two-dimensional electrophoresis (2-DE) results showed that six new specific proteins including C₄ (20.2 kD pI 6.0), F (24 kD pI 6.35), B₃ (22.3 kD pI 6.35), B₄ (23.5 kD pI 6.5), C₅ (21.8 kD pI 5.6), and C₆ (20.2 kD pI 5.6) specifically expressed. C₄ always expressed during SiAR stress. F expressed under the stress of pH 2.5 for 15 days and expressed in all pH SiAR stress for 20 days. The expression of proteins including B₃, C₅, and C₆ was related to pH value and stress intensity of SiAR. The expression of B₄ resulted from synergistic effects of SiAR and Ca. The expression of G₁ (Mr 19.3 kD, pI 4.5), G₂ (Mr 17.8 kD, pI 4.65), G₃ (Mr 16.6 kD, pI 4.6), and G₄ (Mr 14.7 kD, pI 4.4) enhanced under the treatment of 5 mM ethylene glycol tetraacetic acid (EGTA) and 2 mM chlorpromazine (CPZ). These proteins showed antagonistic effects and might be relative to the Ca-calmodulin (Ca-CaM) system of longan in response to SiAR stress.
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