Comparative Analysis On The Characterization Of Non-photochemical Quenching In Zostera Marina And Hedera Nepalensis

The Non-Photochemical Quenching?NPQ?,as the photoprotection mechanisms,play a vital role in avoiding photodamage for land plants and aquatic algae.The characterizations of NPQ in Zostera marina and Hedera nepalensis,were compared to clarify the specificity of photoprotection in marine plants.NPQ induction kinetics,components,photoprotective efficiency and proton gradient were employed in marine angiosperm Z.marina and terrestrial angiosperm H.nepalensis via the chlorophyll a fluorescence technique.Moreover,the sequence characteristics of PsbS protein were investigated in Z.marina utilizing the bioinformatic analysis.The main results showed as following:1.Characterization of non-photochemical quenching in Hedera nepalensisTo examine the characterization of NPQ in H.nepalensis,the kinetics and the protective efficiency of NPQ were investigated via MINI-PAM.With the increase of the light intensity,maximum NPQ(NPQ_max),the quantum yield of regulated non-photochemical energy loss in PSII[Y?NPQ?]and the yield ratio[Y?NPQ?/Y?NO?]significantly increased.Moreover,the protective components of NPQ increased more than the photoinhibition conponent.NPQ_max,the yields for protective components of NPQ,Y?NPQ?and Y?NPQ?/Y?NO?increased in the mature leaf?ML?and decreased in the young leaf?YL?compared to the old leaf?OL?.In OL and YL,the onset of photoinhibition took place at a lower light intensity than in the ML.The pNPQ was higher in the ML,compared with that in the OL and YL.The?pH were investigated in H.nepalensis utilizing the DUAL-PAM-100 equipped with a P515/535 module exhibited the?pH building capacity increased in response to high light exposure.Higher level of the?pH was observed in the ML compared to the OL and YL,indicating that the?pH plays an essential role in NPQ.In conclusion,the NPQ efficiency of H.nepalensis enhanced with the increasing light intensity and were highest in the ML.In contrast with sun plants,H.nepalensis displayed lower NPQ_maxax and protective NPQ?pNPQ?,and was more prone to photoinhibition,both of which means that the photoprotective efficiency was lower in H.nepalensis than in sun plants.2.Characterization of non-photochemical quenching in Zostera marinaNon-photochemical quenching induction/relaxation kinetics,photoprotective efficiency and proton gradient building capacity were investigated in Zostera marina utilizing the chlorophyll a fluorescence technique.Compared with other higher plants,the descending amplitude and recovery rate of the maximum quantum yields of photosystem II?PSII?were lower in Z.marina,indicating the limited resilience of the PSII.The lower NPQ_maxax and the slower NPQ induction rates,could contribute to a much lower capacity for NPQ induction in Z.marina.In parallel,the single exponential function was perfectly fit the NPQ induction kinetics,confirming the absence of the rapid phase?qE?.The quantum yield of non-regulated non-photochemical energy loss in PSII[Y?NO?]significantly elevated in Z.marina compared to H.nepalensis.On the contrary,Y?NPQ?and Y?NPQ?/Y?NO?were gradually decreased in Z.marina.Compared with H.nepalensis,the onset of photoinhibition and pNPQ were lower in Z.marina,collectively indicating a decline in photoprotective capacity.550-515 nm difference signal analysis revealed the formation of a instability?pH.All these results indicated the less photoprotective efficiency of NPQ in Z.marina.3.Phylogenetic and sequence analysis of PsbS protein in Zostera marinaThe exon-intron organization,amino acid sequence,phylogeny,physicochemical property and structures of PsbS protein in Z.marina were investigated via bioinformatic analysis.The psbS gene of 1490 bp consisted of one 5'-UTR,four exons,three introns and one 3'-UTR,and encoded a protein with 271 amino acids with the molecular weight of 28.85 kDa and pI of 9.16.PsbS belonged to the Lhc superfamily,contained a conserved domain of chlorophyll a/b binding protein.Amino acid suquences analysis for PsbS protein showed that Z.marinashares 64-86%homology with other higher plant.Furthermore,PsbS protein in Z.marina was dominatly composed of alpha helix and random coil,which was consist with higher plant.Three-dimensional structure was predicted in Z.marina,Zea mays,Spinacia oleracea and Physcomitrella patens,but no significant differences were found in these species.PsbS protein in Z.marina felled into the clade of monocotyledon and was closer to Spirodela polyrhiza.The light-induced increase of psbS gene was measured in Z.marina as well as in Phyllostachys edulis but no siginificant differences were found between two species.Therefore,these results indicate that the function of PsbS protein in Z.maina and other higher plants have high similarity.