Heterologous Expression of Suaeda aralocaspica SaPEPC2 Gene Improves Drought Resistance and Photosynthesis in Transgenic Tobacco
INTRODUCTION:Phosphoenolpyruvate carboxylase(PEPC)is a key enzyme for C4 photosynthesis that help plants to resist adversity under abiotic stress.Suaeda aralocaspica,an annual halophyte,has gradually developed a single-cell C4 photosynthetic pathway by compartmentalizing a chlorenchyma cell into distal and proximal ends to delineate and form the four-carbon(C4)and three-carbon(C3)cycles through long term of evolution.This unique biochemical compartment-ation pattern holds promise for introducing"C4-like microcirculation"into C3 plants without establishing Kranz anatomy.RATIONALE:The PEPC gene act as an essential component of C4 photosynthesis,but few studies have reported on the PEPC gene in single cell C4-pathway species.To reveal the impact of the SaPEPC2 gene from S.aralocaspica on the photosynthetic performance and drought resistance of C3 plants,we evaluated the drought resistance function and pho-tosynthetic performance of transgenic tobacco(Nicotiana tabacum)overexpressing the SaPEPC2 gene driven by its own promoter(ProsaPEPC2::SaPEPC2)through physiological measurements and gene expression analysis methods.RESULTS:Our findings demonstrated that overexpressing the SaPEPC2 gene in tobacco improved leaf water retention,maintained chlorophyll stability,promoted the accumulation of osmotic adjustment substance,enhanced antioxidant en-zyme activities,reduced ROS levels,mitigated the extent of membrane damage,upregulated the expression of drou-ght-related and endogenous photosynthesis genes,and increased PEPC enzyme activity and net photosynthetic rate.CONCLUSION:In conclusion,overexpressing the SaPEPC2 gene likely facilitates the formation of a"C4-like microcircula-tion"pathway in tobacco.These results may provide the theoretical foundation for the potential utilization of the single-cell C4 pathway PEPC genes from S.aralocaspica to breed high light-efficiency and stress-resistant crop varieties.
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