To study the photosynthetic and physiological response of maize C4-type PEPC(phosphoenolpyruvate carboxylase gene)and PPDK(pyruvate phosphate double kinase gene)dual-gene wheat to high light,the ZmPEPC+ZmPPDK wheat lines PCK30 and PCK60 and their wild type control material(WT)were used as experimental materials.The relative expression levels of exogenous genes in transgenic wheat were identified.The photosynthetic enzyme activity,chlorophyll content,gas exchange parameters,chlorophyll fluorescence parameters,active oxygen content,and antioxidant enzyme activity of transgenic wheat were measured under normal light intensity(NL)and high light stress(HL)at heading and grain-filling stages.The results showed that the two transgenic lines expressed the PEPC and PPDK genes efficiently at the transcriptional level.The enzyme activity of PEPC,PPDK,NADP-ME,and Rubisco of transgenic wheat was significantly higher than WT under NL or HL stress at different stage,and the increase of WT was more obvious under HL stress.Compared with NL stress,the chlorophyll content of transgenic wheat and WT decreased significantly under HL stress,but the decrease of transgenic lines was smaller,and the chlorophyll content of transgenic lines was significantly higher than WT under HL stress.Under two treatment stresses,the net photosynthetic rate(Pn)of PCK30 and PCK60 was significantly higher than WT,and the higher range was more obvious under HL stress.The increases were 15.26%and 17.57%at heading stage and 13.41%and 15.82%at grain-filling stage,respectively.The variation trend of stomatal conductance,Fv/Fm and qp was consistent with Pn,while the variation trend of intercellular carbon dioxide concentration was opposite to Pn.The content of reactive oxygen species and malondialdehyde produced by transgenic lines under HL stress was significantly lower than WT,while the trend of antioxidant enzymes was opposite.In two consecutive years of field plot yield experiments,PCK30 and PCK60 were 8.37%and 10.16%higher than WT on average.The overexpression of PEPC and PPDK in wheat enhanced the endogenous photosynthetic enzyme,photochemical efficiency,and antioxidant enzyme activities of wheat,enhanced the stability of leaf cell membrane under high light stress,protected the photosynthetic apparatus,and maintained a high photosynthetic efficiency,thus improving the tolerance of transgenic wheat to high light stress.
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