The Switch Of Red-shifted Chlorophyll Coordinated Amino Acid In Light-harvesting Antenna Proteins LHCA1 And LHCA2 And Their Effects On Fluorescence Characteristics

There are four main protein complexes involved in photoreaction on plant photosynthetic membranes,which are photosystem II(PSII),cytochrome b6 f complex,photosystem I(PSI)and ATP synthase,of which PSII and PSI bind a large amount of pigment Molecules(such as chlorophyll,carotenoids,etc.)also drive the absorption,transmission,and transformation of light energy.The PSI light-harvesting antenna LHCI is composed of four antenna proteins,LHCA1?LHCA2?LHCA3 and LHCA4,each combined with a pair of special chlorophyll molecules(Chl a603-609).They are called red-shifted chlorophyll(red Chls)because of their longer absorption wavelengths.They can extend the light-harvesting ability of the plant PSI-LHCI to the infrared spectral region.The 4 pairs of red-shifted chlorophyll molecules in PSI-LHCI occupy a key position in the energy transfer pathway,which has a significant impact on the energy transfer process.The red-shifted degree of red Chls in the four LHCA antenna proteins is not the same.The red-shifted degree of LHCA3 and LHCA4 is greater than that of LHCA1 and LHCA2.The red-shifted degree of red Chls affects the energy transfer process.Therefore,the reasons for the red-shift of red Chls are important meaning.Based on the previous in vitro experiments,it is believed that the different coordination amino acids of red-shifted chlorophyll Chl a603 cause different degrees of redshift.The coordination amino acids of LHCA1 and LHCA2 are histidine(His),and the coordination amino acids of LHCA3 and LHCA4 are asparagine(Asn),Asn coordination will cause a greater degree of redshift than His coordination.In this paper,Arabidopsis thaliana was used as a material to mutate the coordination amino acid His in LHCA1 and LHCA2 to Asn,to determine the red shift of the light absorption wavelength of PSI-LHCI in transgenic plants,and to analyze the photosynthetic physiological characteristics of LHCA antenna deletion mutants for the purpose of changes The physiological characteristics of the plant after the coordination of amino acids lay the foundation.The main research results of this paper are as follows:(1)LHCA1(H79N)and LHCA2(H99N)overexpression vectors were constructed,and 5and 6 transgenic overexpression plants with Arabidopsis lhca1 and Lhca2 mutants as backgrounds were obtained respectively.(2)Measure the fluorescence emission spectrum of LHCA1(H79N)and LHCA2(H99N)transgenic plants at 440 nm using a low temperature fluorescence spectrophotometer(F-4700).Compared with the wild type,the absorption wavelength of the transgenic plants overexpressed in the light-harvesting antennas LHCA1 and LHCA2 coordinated with the red-shifted chlorophyll histidine His to asparagine Asn was not red-shifted,but different.The degree of blue shift is different from the results reported in in vitro studies.(3)In order to study the physiological characteristics of LHCA1(H79N)and LHCA2(H99N)transgenic plants,the physiological characteristics of Arabidopsis LHCI antenna mutants under strong light were first analyzed.The study found that compared with other mutant materials,the photosynthetic parameters Fv/Fm,Y(I),Y(II),ETRI,ETRII and Vio contents of the lhca4 mutant decreased most rapidly after strong light treatment,and Y(ND)and The accumulation of Zea is the fastest growing.The loss of LHCA4 under strong light will cause more damage to the optical system than the loss of other antennas,which shows the importance of LHCA4 gene in plant photoprotection and LHCA4 is the antenna with the greatest degree of redshift.The relationship between red-shifted chlorophyll and light protection needs further study.