Effect Of Co-transformation Of Photorespiration Pathway Gene On Photosynthetic Physiology And Yield Of Transgenic Forage

Photorespiration is a complex metabolic process in which green plants consume O₂and release CO₂under light.The process of photorespiration requires a lot of energy consumption,which greatly reduces the photosynthetic efficiency of plants,resulting in a significant decline in plant yield.In recent years,the improvement of plant photorespiration pathway has gradually become one of the research hotspots in plant high-yield breeding.Stylosanthes guianensis SW.is a kind of legume forage widely planted in the tropics.It has a high content of crude protein and is often used as animal feed and plant green manure.Alfalfa（Medicago sativa L.）is a kind of legume forage widely planted in temperate areas.It has high nutritional value,long service life and stable productivity.It is a high-quality feed loved by livestock.In order to popularize planting,the current researches on genetic engineering breeding of S.guianensis and alfalfa are mostly focused on stress resistance,but lack of high-yield breeding.In this study,legume S.guianensis and alfalfa were used as experimental materials to transfer TG1 and DEF2,which contain the key genes of glycolic acid metabolism pathway of Escherichia coli,and a new photorespiration pathway was constructed.By measuring the photosynthetic related physiological indexes,biomass and other data of transgenic plants,and comparing with wild-type plants,the influence of the establishment of the photorespiration branch on two kinds of forages was obtained,so as to provide a new direction for the cultivation of new high-yield S.guianensis and alfalfa lines,and for the research of high-yield forage breeding.Through PCR detection and semi quantitative RT-PCR detection,three T2 generation S.guianensis homozygous lines containing TG1 and DEF2 and four transgenic alfalfa homozygous lines containing TG1 and DEF2 were finally verified.A variety of physiological indexes of wild type,transgenic S.guianensis and alfalfa were measured.Firstly,the photosynthetic physiological indexes of transgenic plants were measured and compared with wild type.The results showed that the photosynthetic rate of transgenic S.guianensis and alfalfa decreased and the net photosynthetic rate increased.In addition,compared with the wild type plants,the CO₂compensation point of transgenic plants decreased and the photosynthetic rate of CO₂saturation point increased.These data show that the establishment of a new photorespiration branch can effectively inhibit the photorespiration process and improve the photosynthetic efficiency of the two forages.After that,the biomass of the transgenic plant was measured and compared with the wild type.The experimental results showed that the plant height,branches and leaves of transgenic S.guianensis and alfalfa increased,which increased the fresh weight of the aboveground.In addition,the seeds of transgenic S.guianensis increased,and the weight of seeds per plant increased.All the above experimental results show that with the transfer of TG1 and DEF2 carriers,a new photorespiration branch is constructed in plants,which can effectively inhibit the photorespiration of plants and improve the photosynthetic efficiency,thus significantly improving the biomass of transgenic S.guianensis and alfalfa.