Silicon improves photosynthetic performance by optimizing thylakoid membrane protein components in rice under drought stress

For revealing the internal mitigation mechanism of silicon to drought stress, a super high-yield hybrid rice LYP9 was employed to study the change of photosynthetic fluorescence, structure and composition of thylakoid membrane as well as its physiological property by polyethylene glycol (PEG) and silicon (Si) treatment. Results showed that K step appeared in OJIP transient and ET0/RC, ET0/CS0, φE0 of rice seedlings were decreased under drought stress, while these parameters were increased by applying silicon. We found that silicon application could relieve the degradation of membrane protein complexes under drought condition, such as supercomplexes, PSI core binding LHCI, PSI core, F1-ATPase binding Cytb6/f complex, PSII core, trimeric LHCII and monomeric LHCII. Thylakoid membranes proteins were further detected by BN-SDS-PAGE, 20 differential protein spots between PEG treatment and PEG treatment applying with silicon were identified. These alterations were involved in light harvesting, stability of PS I, function of PS II reaction centers, electron transport, PS II core antenna content, and consequent synthesis of ATP. Our results indicated that Si treatment might play roles in absorption, transformation and transfer of light energy by optimizing the thylakoid membrane protein components in rice seedlings under drought stress observed by BN-PAGE and BN-SDS-PAGE.