Functional Analysis Of GhPsbS Gene In Upland Cotton Photosynthetic System Ⅱ Under Different Light Intensities

Object:Cotton（Gossypium）is one of the most important economic crops in daily life of human beings.It is also an indispensable fiber crop.In recent years,abiotic stress factors often affect cotton yield and quality in many ways,and light conditions are also non-living.One of the factors is that most crops are often in a state of excess light energy under natural conditions.Plants also exhibit photoinhibition under strong light,and photoinhibition reduces the photosynthetic capacity of the crop and inactivates the photosynthetic apparatus.Related studies have found that PsbS gene plays an important role in photoprotection and non-photochemical quenching.At present,there are many reports on the cloning and research of plant photosynthetic system related genes,including Arabidopsis thaliana,rice,bamboo,and Southeast Sedum.The sequence of the PsbS gene of several species has been published and reported,but there are few reports on the PsbS gene in upland cotton（Gossypium hirsutum Linn.）.This group has previously cloned and preliminarily expressed the gene.Based on the obtained cloned cotton photosynthetic system Ⅱ PsbS gene,this study studied the mechanism of the gene in photosystem Ⅱ photoprotection.By increasing photosynthetic capacity and increasing cotton yield,it lays a theoretical foundation for high-efficiency cotton breeding.Method:In this study,the tobacco（Nicotiana tabacum xanthin）T3 strain and the non-transgenic（general wild type,wt）tobacco transgenic with GhPsbS gene were used as materials to compare the biological traits（plant height,dry weight,leaf area,chlorophyll content）.And carotenoid content),physiological traits under different light intensities(75,240,450,600μmol·m^-2·s^-1)（antioxidant enzymes SOD,POD,CAT）;photosynthetic enzyme RUBP,PEPC;Fo,Fm,Fv/Fo,Fv/Fm,φEo,PI_ABS,NPQ,ΦPSⅡ,ETR,qP and other chlorophyll fluorescence characteristics;net photosynthetic rate（Pn）,stomatal conductance（Gs）,intercellular CO₂ concentration（Photosynthetic indicators such as Ci）,transpiration rate（Tr）,and the difference between inhibitor treatment（DTT,DCCD）,and the difference in expression between different strains under different treatments.Evaluation of the glare-tolerant stress of the gene by correlation analysis.The resistance to strong light stress was evaluated;The transgenic cotton plants transgenic with pGWB17-GhPsbS gene,the cotton plants transfected with 35HK-GhPsbS gene and the control plants（YZ-1）were used as materials to measure the expression,chlorophyll fluorescence and photosynthetic characteristics of the corresponding plants,and the GhPsbS gene was analyzed comprehensively.The function in cotton photosynthesis.Result:1)The phenotypic characteristics of tobacco lines transfected with GhPsbS gene were significantly different from those of wild type（WT）tobacco.The tobacco leaves transferred to PsbS gene grew faster than wild type tobacco leaves in the pre-growth stage,and the same growth conditions.The leaf area,plant height,dry weight and fresh weight of the two transgenic GhPsbS tobacco lines were significantly higher than those of wild type tobacco(light intensity was 240μmol·m^-2·s^-1and temperature was 25℃).2)The expression level of tobacco transferred to GhPsbS gene was significantly higher than that of wild type,and under normal growth light intensity of 240μmol·m^-2·s^-1,the expression levels of three lines of transgenic lines were wild type 5.2.4.6 times,6.9 times,then reduce or increase the light intensity,the expression level of the transgene is still higher than that of the wild type.After different light intensity treatment and different inhibitor treatment,the transgenic tobacco expression is significantly higher than that of the transgenic tobacco.Wild type;3)The chlorophyll content of transgenic tobacco is also different from that of wild type tobacco.The chlorophyll a and b content of L3 in transgenic lines are the highest,1.39 and 1.62 times of wild type,respectively,and the carotenoid content is higher than wild type.39%,indicating that the transgenic GhPsbS gene can increase the chlorophyll a,chlorophyll b and carotenoid content of tobacco;4)The activity of tobacco antioxidant enzymes SOD,POD and CAT of GhPsbS gene was lower than that of wild type tobacco,indicating that the GhPsbS gene was transferred to reduce the antioxidant enzyme activity of the plant,while the photosynthetic enzyme PEPCase of the transgenic line was high under high light intensity.In wild type,RUBPCase is lower than wild type;5)The differences of chlorophyll fluorescence characteristics between transgenic lines and wild type were compared.It was found that the fluorescence parameters Fo,Fv,Fm,Fm/Fv,PI_ABS,NPQ,ΦPSⅡ,qP,ETR,φEo of transgenic lines were higher than wild.Type tobacco;it shows that the PsbS gene can actually improve the light energy capture ability and electron transport ability of plants;6)Under different light intensities,tobacco plants transfected with GhPsbS gene have higher net photosynthetic rate（Pn）,stomatal conductance（Gs）and transpiration rate（Tr）,while wild type is intercellular CO₂ concentration（Ci）.Higher,resulting in a higher wild type Ci than the transgenic line is caused by non-stomatal factors;7)After treatment with DTT and DCCD,the chlorophyll fluorescence and photosynthetic capacity of transgenic tobacco lines decreased significantly,while the decrease of NPQ in plants caused by the use of inhibitor DTT was much greater than that of NPQ after using DCCD.Both lutein cycle and thylakoid membrane proton gradient play an important role in tobacco NPQ;8)The expression level,chlorophyll a,b and carotenoid content,chlorophyll fluorescence characteristics and photosynthetic characteristics of transgenic overexpressing cotton were higher than those of interfering cotton plants,indicating that the presence of this gene can enhance the photosynthetic capacity of plants and provide cotton breeding.The theoretical basis.