The Response Of Physiological And Proteomic Levels In Magnolia Officinalis Sub.bilobais Under Drought Stress

Magnolia officinalis subsp.bilobais precious tree used for Medicinal,timber and ornamental functions.In the natural distribution area,frequent seasonal drought limits the regeneration and affects yield and quality of Magnolia officinalis subsp.biloba.Meanwhlie,under the stress of human excessive deforestation and a large number of stripping bark used for medicinal.The natural number of Magnolia officinalis subsp.biloba became rare.It is useful to study the physiological response and the related protein expression of Magnolia officinalis to drought stress,which is helpful to reveal the adaptability and adaptability mechanism of Magnolia officinalis subsp.biloba to drought stress and to improve the drought resistance of Magnolia officinalis and guide the breeding of Magnolia officinalis.In this paper,the morphological indexes,soil water content(SWC),leaf water content(LWC),leaf water potential(LWP),photosynthetic characteristics and other physiological indexes of Magnolia grandiflora seedlings were monitored once every six days after irrigation under drought stress were studied by pot experiment.The drought persisted for 0~30 days.The differentially expressed proteins were analyzed by two-dimensional electrophoresis and MALDI-TOF-MS method for Magnolia officinalis subsp.bilobaunder drought stress.The main results are as following:1.With the deepening of the degree of drought,leaf wilting and leaf blade degree gradually increased.SWC was 11.88%when the leaves were yellow,spots and other injuries,SWC was 7.37%when the edge of the leaves curled,drooling,SWC was 3.93%above the ground part of the water loss.Under drought stress for 6～30 d treament,SWC and LWC were significantly decreased.On day 30,SWC was only 13.86%of contrast group.After 12 d treament,LWP ropped sharply.LWP dropped to to-4.65 Mpa after 30 d treament.The relative content of chlorophyll in SPP decreased with the decrease of SWC.Under the drought stress,the water physiological state of the leaves was decreased and the chlorophyll content was significantly decreased.2.The Pn,Tr and Gs of leaves of Magnolia officinalis subsp.bilobadecreased significantly under drought stress,and Ci decreased first and then increased.PWUE was ascend in first and descend at last.The photosynthesis of Magnolia officinalis subsp.biloba was influenced by the combined action of stomatal and non-stomatal factors.At the beginning of drought(after 0～18 d treament),stomatal factors played a leading role,but during late drought(after 18 d treament)non-stomatal factors were more important ones.The initial fluorescence(Fo)increased first and then decreased.The maximum photochemical efficiency(Fv/Fm),the actual photochemical efficiency(ΦPSⅡ),the apparent photosynthetic electron transport rate(ETR)decreased with the increase of drought stress.After 24 d treamenr,the photosynthetic mechanism of Magnolia officinalis subsp.biloba was destroyed.Fv/Fm,ΦPS II,ETR,respectively,from 0.79,0.65,21.84 down to 0.42,0.41,3.93.The photosynthetic characteristics were significantly correlated with SWC and LWP(P<0.01).Porosity was the dominant factor affecting photosynthetic parameters.3.The content of proline(Pro)under drought stress increased first and then decreased with the decrease of SWC.The content ofproline reached the peak at the 18th day(29.96 μg·ml-1),which Compared with the control group increased by 250.1%.The decrease of LWC decreased from 0 to 18 days under drought stress,which was related to osmotic regulation.The content of MDA was significantly increased under drought stress,and the highest at 24 days(32.34 nmol·ml-1),which was 121.4%higher than that of control group.4.A two-dimensional gel electrophoresis system for the whole protein of Magnolia officinalis leaves was established,and the extraction methods of the three proteins were compared.The optimum loading conditions and isoelectric focusing conditions were screened.The results showed that TCA/acetone+Tris-phenol method had the best protein for the leaves of Magnolia officinalis Leaves,17cm pH5-8NL IPG strips were used,the sample loading was 17 μg,the SDS-PAGE concentration was 10%,2-DE separation and silver staining were carried out according to IEF program II,and the 2-DE images with clear resolution and high stability was obtained.5.On the basis of the 2-DE optimization system,the difference between the control group and the 2-DE after 12 d treament.A total of 45 significant differences in protein spots were found(Ratio>2,p≤0.05).Among them,there were 10 proteins with abundance uplift,18 proteins were down-regulated,10 new protein spots and 7 protein spots were lost.A total of 32 differentially expressed proteins were identified by MALDI-TOF-MS analysis and NCBI,Uniport and other database searches.6.COG functional classification,GO annotation analysis and analysis of KEGG pathway were successfully performed on 32 proteins.The results showed that the differential proteins identified in the young leaves of Magnolia officinalis subsp.biloba were related to cell structure(3.13%),amino acid transport and metabolism(3.13%),photosynthesis(9.38%),post-translational modification,protein transformation,molecular chaperone 12.50%),energy production and conversion(15.63%),carbohydrate transport and metabolism(21.88%),unknown functional protein classification(34.38%).There are 20 enzymes involved in 18 metabolic pathways,including photosynthetic carbon fixation pathway has 8 enzymes involved in carbon metabolism with eight enzymes involved in photosynthetic pathways involved in seven enzymes,glyoxylate and dicarboxylate Acid metabolism has four enzymes involved,glycolysis and gluconeogenesis and amino acid synthesis pathway of the three enzymes involved.These proteins are involved in a number of physiological processes to achieve the metabolic balance of the seedlings of Magnolia grandiflorum under drought conditions,and the protein expression pattern is consistent with the pattern of physiological and biochemical changes.