Studies On Structure Identification And Detection Of Phytochelatins In Rice Seedlings Under Cadmium Stress

Phytochelatins is a polypeptide structure produced in rice plant,which can alleviate the heavy metal toxicity and balance the intracellular metal ion balance,and also a good biological indicator of metals(especially cadmium).Rice is the main food crop in China and has strong ability to absorb cadmium.It is important to improve the mechanism of anti-heavy metal stress in rice by reinforcing the study of phytochelatins.At present,the research on this aspect mainly focus on the synthesis pathway of phytochelatins,the physiological and biochemical functions and the interaction with heavy metals,while the relevant study on the structural identification of phytochelatins is relatively few.In this study,the indica rice variety 9311 was used as an example to establish a method for the identification of phytochelatins in rice.The method was analyzed by liquid chromatography-tandem mass with high-resolution technique and development the liquid chromatography-tandem mass spectrometry.As a result,the content of phytochelatins in different parts of rice plants under different Cd stress was analyzed.The research contents are as follows:1.A method for the identification of phytochelatins and their derivatives was established.The aerial parts and root extracts of rice were scanned by liquid chromatography tandem mass spectrometry,and the suspected PCs structure was screened by selective scanning mode combined with primary mass spectrometry and secondary mass spectrometry(characteristic ion).The results were analyzed by high-resolution mass spectrometry,and the abundance aberration of the extracted parent ions was analyzed.The structure of the ions with characteristic ions was screened out.The exact mass of the primary and secondary mass spectra,the debris Ion and the actual scan of the secondary mass spectrum were used for further determination of the phytochelatins structure.Besides,the identification of the phylogenetic phytochelatins was confirmed by external synthesis analysis,meanwhile the peak time,molecular ion peak isotope abundance,exact mass number and secondary fragment ion were identified.2.A qualitative and quantitative method for the determination of phytochelatins and their derivatives by liquid chromatography tandem mass spectrometry was established.The extraction efficiency of different phytochelatins was studied,and the LC-MS / MS detection method of 12 phytochelatins was established.The detection limit of the 12 kinds of phytochelatins was 10-63 ?g/L,with the limit of quantification was 30-189 ?g/L.The recoveries were 61-109%(GSH: 50,100,250 mg/kg;other phytochelatins: 4,8,20 mg/kg)and the relative standard deviations were 2.1-13.8%.The method is stable with good peak shape,and suitable for qualitative and quantitative analysis of plant phytochelatins and their derivatives.3.Based on the above results,the relationship between the concentration of cadmium in rice and the 12 phytochelatins in rice under different Cd stress was analyzed by quantitative analysis of phytochelatins.The results showed that the cadmium concentration in overground part was lower than that in the roots,and the content of cadmium was 26.8 mg inoverground part and 89.4 mg in the root.Cadmium stress could promote the synthesis of large amounts of glutathione and the resistance to heavy metals in the shoots was dominated by glutathione.The content and quantity of phytochelatins in the shoots and roots of rice increased gradually under the high concentration of cadmium stress.