| Cassava(Manihot esculenta Crantz),a species of cassava from Euphorbia,originated from tropical American shrubby perennial crops.It was introducted to China in 1820s,Cassava is a kind of plant with strong stress resistance,which has the characteristics of drought resistance,poor tolerance,wide adaptability,high starch yield and so on.In this study,cassava sexual tetraploid and its maternal diploid SC5 were used as the materials to determine the photosynthetic capacity and to compare the total protein of the parents SC5 and F1 tetraploid.The physiological and biochemical determination combined with proteomic technology were applied to study the physiological and biochemical characteristics and analyze the changes in the proteome of the leaves of the sexual tetraploid and SC5 under drought stress,salt stress and low temperature stress.The two-dimensional electrophoresis technique was used to construct the full protein expression maps of sexual tetraploids and SC5.According to map analysis software and mass spectrometry,proteins related to photosynthesis and stress resistance were identified.Analyze the metabolic pathways involved in differential proteins,understand their response mechanisms to stress,provide a theoretical reference for revealing the molecular mechanism of cassava stress resistance at the protein level and screening cassava stress resistant germplasm.The results of the study are as follows:1.The net photosynthetic rate of sexual tetraploid leaves was significantly higher than that of SC5.At the protein level,the expression levels of proteins involved in photosynthesis in the leaves of the sexual tetraploid is significantly extremely higher than of SC5,have confirmed the high photosynthetic capacity of sexual tetraploid.2.Two-dimensional gel electrop-horesis(2-DE)was used to analyse leaves of cassava sexual tetraploid and SC5,after analysed by Delta 2D software,49 differential protein spots were detected in the leaves of sexual tetraploid compared with SC5,of which 23 were up-regulated and 26 were down regulated.42 proteins were matched by the mass spectrometric analysis of the differential protein spots and the comparison of the NCBI database.Their biological functions mainly involve photosynthesis,carbohydrate and energy metabolism,chaperone protein,structural protein,protective protein,detoxification and antioxidant protein,DNA/RNA binding protein,protein biosynthesis,signal transduction mechanism and so on.The transcription level of 11 differential protein spots was verified by qRT-PCR.It was found that the expression of the 11 differential protein spots was not completely consistent with that at the protein level.3.Under three kinds of stress,according to morphological combined with the physiological and biochemical indicators and proteomics analysis,we can see that under the drought stress and salt stress,sexual tetraploid can respond to stress more effectively than SC5,and can be better adapted to the bad environment,with more strong drought resistance and salt tolerance.However,under low temperature stress,sexual tetraploids do not have cold tolerance advantage over SC5.4.Two-dimensional gel electrop-horesis(2-DE)was used to analyse leaves of cassava sexual tetraploid and SC5 under stress,after analysed by Delta 2D software,34 differential protein spots were detected in the leaves of sexual tetraploid compared with SC5 under drought stress,of which 18 were up-regulated and 16 were down regulated.29 proteins were matched by the mass spectrometric analysis of the differential protein spots and the comparison of the NCBI database.15 differential protein spots were detected in the leaves of sexual tetraploid compared with SC5 under salt stress,of which 6 were up-regulated and 9 were down regulated.13 proteins were matched by the mass spectrometric analysis of the differential protein spots and the comparison of the NCBI database.29 differential protein spots were detected in the leaves of sexual tetraploid compared with SC5 under low temperature stress,of which 14 were up-regulated and 15 were down regulated.19 proteins were matched by the mass spectrometric analysis of the differential protein spots and the comparison of the NCBI database.Their biological functions are mainly related to photosynthesis,carbohydrate and energy metabolism,chaperones protein,detoxification and antioxidation and so on.5.This study found that the expression of Ribulose bisphosphate carboxylase and PSII oxygen enhanced protein 1 increased in response to drought stress.It is suggested that the sexual tetraploid can more effectively maintain the structure and function of the photosynthetic system than SC5,to obtain nutrients necessary for growth and development,and thus more quickly adapt to drought stress.The expression of RCA was up-regulated in response to salt stress.It is presumed that it is possible to make the sexual tetraploid synthesize organic matter by immobilizing more carbon than SC5 to meet the plant’s demand for energy,so as to improve the salt resistance;the expression of the chaperone protein chloroplast-related is down,presumably the sexual tetraploid can better respond to salt stress to reduce its own nutritional consumption compared with SC5.Many proteins in response to low temperature stress associated with carbohydrates and energy metabolism are up-regulated.It is speculated that proteins related to carbon energy metabolism can timely provide the carbon source and energy consumed by low temperature stress. |
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