Abstract:
Synechocystis sp.PCC 6803 is suitable for studies of photosynthesis.Further,
slr1122 encodes an unknown protein of 250aa,which possibly interacts with a hybrid sensory kinase encoded by
sll1672 (Hik12).Via pull-down assay, we verified that Slr1122 interacted with Sll1672.With the isotope assay of
32P,the auto-phosphorylation of Hik12 decreased in the presence of Slr1122,indicating that Slr1122 regulated the two-component system.By homologous double-crossover,
slr1122 was replaced with antibiotic resistance cassettes kanamycin,resulting in the knockout mutant of
Synechocystis sp.PCC 6803,Δ
slr1122.We found that in Δ
slr1122,the transcription of the key PSⅡ component gene,
psbAI (slr1181),decreased remarkably,leading to low capacity of photosynthesis and low growth rate of Δ
slr1122 compared with the wild type.In addition,Δ
slr1122 became more sensitive to light.Under low light,Δ
slr1122 caught more light and grew more rapidly,with the opposite occurring under high light,and thus Δ
slr1122 was more liable to photodamage.Δ
slr1122 had lower content of phycobiliprotein and photosynthetic pigments,particularly carotenoids.RT-PCR showed that the five important genes involved in carotenoid biosynthesis were transcribed more lowly.Coincident with this,Δ
slr1122 was more sensitive to redox stress and high light stress.In conclusion,Slr1122 was involved in the regulation of phosphorylation of Hik12 and thereby influenced the biosynthesis of carotenoids.