Proteome Studies Of Bletilla Striata Leaves In Response To Shelter Covering

Bletilla striata will be stressed in high illumination environment,resulting in yellow tip and short plant,which will affect the yield and quality.Shading can effectively solve the problem of high illumination inhibition by reducing the light intensity of plant canopy without changing the spectral structure.In order to explore the physiological changes and molecular mechanism of Bletilla striata under different light conditions,this study set three gradients of light intensity(50%,70%,90%shading rate),and the full sunlight was taken as the control(CK).The morphological structure,molecular mechanism of proteomics,active components and yield were studied in Bletilla striata.The main results are as follows:(1)The indexes of plant height,leaf area,root length,aboveground biomass and yield showed that different shading treatments had significant effects on the morphological indexes in Bletilla striata.Compared with CK,the plant height,leaf area,root length,and aboveground biomass of Bletilla striata were increased under50%,70% and 90% shading treatments while the tuber yield was significantly increased under 50% and 70% shading treatment.Among them,the above indexes were increased most significantly after 50% shading treatment,which showed that Bletilla striata had excellent morphology and good yield after 50% shading treatment.(2)In this study,the proteomic libraries were constructed from Bletilla striata leaves under 50% shading and CK treatments,and a total of 421 differential proteins were identified by TMT-labeled proteomics technology(P<0.05),of them 256 were up-regulated(fold change≥1.3)and 165 were down-regulated(fold change≤0.7).According to the results of proteomics analysis,the Chla/b light-catching complex proteins(LHCA1,LHCA3,LHCB4,LHCB5,CABs),PSII reactive center proteins(PSBQ,PSBP,PSBH,PSBB,PSBC,PSBD),PSI reactive center proteins(PSBR,PSBE,PSSAG,PSAD,PSAC,PSAN),cytochrome b6f(PETC,PEDD),plastid blue protein(PETE)and ribulose bisphosphate carboxylase(rbc L)were significantly increased in 50% shading treatment,indicating that the photosynthetic rate and sugar accumulation were increased by increasing the light harvesting ability,photosynthetic electron transfer efficiency and carbon fixation rate after moderate light reduction.The expression levels of glutathione transferase(GSTF1),S-adenosylmethionine synthetase(SMS,METK5),catalase(CAT),superoxide dismutase(SODCP)and secondary metabolites synthesized enzymes including 4-coumaroyl-Co A ligase(4CLL),flavonoid 3’ hydroxylase(F3’H),and flavonoid 3’5’ hydroxylase(F3’5’H)that regulate the redox process are also increased in the 50% shade environment,which speculated that 50% shading treatment promoted the activities of antioxidant system and flavonoid accumulation in Bletilla striata leaves.Meanwhile,the expression levels of fructose diphosphate aldolase(FBA)and glyceraldehyde-3-phosphate dehydrogenase(GAPDH)involved in carbon metabolism and sugar carrier protein(STC)were also increased,suggesting that 50% shading treatment is beneficial to maintain an efficient carbon metabolism environment and facilitate the transport of small molecules.(3)The medicinal components of Bletilla striata are mainly concentrated in tubers.In this study,the determination of total phenol content,polysaccharide content,polysaccharide yield and total antioxidant capacity of Bletilla striata tuber showed that the total phenol content,polysaccharide content,polysaccharide yield and total antioxidant capacity were all increased with the increase of shading degree,and reached the highest level after 50% shading treatment.The content of flavonoids after shading treatment was significantly increased in Bletilla striata tuber.Further correlation analysis of these indicators revealed that the polysaccharide content and total phenol content in Bletilla striata tuber had a significant positive correlation with total antioxidant capacity(p < 0.05),suggesting that polysaccharide and total phenol were the main effective substances participating in the antioxidant activity of Bletilla striata tuber,and the shading treatment was beneficial to the accumulation of active components in Bletilla striata tuber.In conclusion,the photosynthetic efficiency and carbon fixation rate were increased by increasing the photosynthetic area,Chla/b light-harvesting complex protein,photosynthetic electron transport protein,and carbon fixation related protein expression in Bletilla striata S50 shading treatments,thereby improved the morphology and yield of Bletilla striata.The high expression level of enzymes related to flavonoid synthesis and glucose metabolism was conducive to the accumulation of flavonoids and small molecular metabolites in Bletilla striata leaves,which were transported across the membrane by sugar carrier protein(STC),and then accumulated in the tubers,improving the content of effective ingredients in Bletilla striata tubers.To sum up,50% shading treatment improved the morphology of Bletilla striata,and increased the yield and quality of tubers.