Effects Of Cadmium Stress On Physiology Of Pea At Early Growth Stage And Analysis Of Gene Expression Characteristics Of Chlorophyll Metabolism Pathway

Cadmium pollution is one of the reasons for crop yield reduction and quality reduction,which affects the normal growth and development of plants.Therefore,it is of great significance to study the toxicity of cadmium stress on crops,its mechanism and control.In this experiment,pea JI992 was used as the research material,and different concentrations of cadmium?0.01-0.04 mM CdCl2?were used in the germination and seedling stages to investigate the physiological response of pea to cadmium stress and to explore its molecular mechanism from the gene expression level.The results are as follows;?1?Effects of cadmium stress on germination of peas for 10 days:CdCl2 inhibited the growth of pea rhizomes in a concentration-dependent manner,and 0.03 and 0.04 mM CdCl2 completely inhibited the growth of rhizomes after 10 days of stress.The contents of chlorophyll a,chlorophyll b and chlorophyll a+b in leaves of pea plants treated with different concentrations of CdCl2 were significantly lower than those of control plants?P<0.05?.All concentrations of CdCl2 increased the activities of antioxidant enzymes POD,CAT,APX and soluble protein in the leaves of stressed plants,but decreased the activity of SOD.Real-time quantitative PCR results showed that chlorophyll synthesis related genes?GSA,ALAD,PPOX,CHLI,CHLD,CHLH,EF-TU,GUN4,CHLM,psCHL27,POR,DVR,CHLG?and chlorophyll degradation-related genes were down-regulated by different concentrations of cadmium stress.?CLH,HCAR,NOL?and antioxidant enzyme-related genes?CuSOD,MnSOD,FeSOD,2cprx,GR?and redox protein genes?TRX-F,TRX-M1?,but up-regulated antioxidant enzymes?CAT,PRX,APX?expression levels.?2?Effects of cadmium stress on peas at seedling stage for 20 days:CdCl2 inhibited the growth of pea rhizomes in a concentration-dependent manner;with the increase of CdCl2 concentration,the contents of chlorophyll a,chlorophyll b and chlorophyll a+b increased first and then decreased.The trend was higher than that of the control when treated with 0.01 and 0.02 mM CdCl2;the treatment with 0.03 and 0.04 mM CdCl2 was lower than the control;the Fm,Fv/Fm,qP and ETR of chlorophyll fluorescence parameters were inhibited by cadmium stress to varying degrees.The tolerance of F₀ and NPQ increased with the increase of tolerance;the activities of antioxidant enzymes POD and SOD increased with the increase of cadmium concentration,while the activities of antioxidant enzymes CAT and APX decreased with the content of soluble protein;real-time quantitative PCR The results showed that different concentrations of cadmium stress down-regulated chlorophyll synthesis related genes?HEMA,GSA,ALAD,CHLI,CHLD,CHLH,CHLM,EF-TU,CHLM,DVR,CHLG,psCAO?and antioxidant enzyme-related genes?CAT,GR,APX?and oxidized protein gene?TRX-F?expression levels.0.02 mM CdCl2 significantly down-regulated the expression levels of chlorophyll degradation-related genes?NOL,NYC1,HCAR,CLH,PPH,PAO1,NYE1,SGR?.?3?Effects of cadmium stress on seedling peas for 40 days:CdCl2 inhibited the growth of pea roots in a concentration-dependent manner.Most pea plants died when cultured to 40 days.Different concentrations of cadmium stress reduced chlorophyll a,chlorophyll b and chlorophyll in leaves.The content of chlorophyll b and chlorophyll a+b was small after a+b content and 0.02 mM CdCl2 treatment.The chlorophyll fluorescence parameters Fm,Fv/Fm,qP and ETR decreased in concentration,and F₀ and NPQ increased significantly?P<0.05?;POD activity of pea leaf antioxidant enzyme activity increased gradually with the increase of cadmium concentration,SOD,CAT and APX activity showed opposite trend,soluble protein content was significantly higher than that of control at 0.01 and 0.02 mM CdCl2?P<0.05?.,0.03 and 0.04 mM CdCl2 treatment was significantly lower than the control?P<0.05?;with the increase of cadmium stress,chlorophyll synthesis related genes?HEMA,GSA,ALAD,PPOX,CHLI,CHLD,CHLH,CHLM,EF-TU,GUN4,psCHL27,POR,DVR,CHLG,psCAO?and chlorophyll degradation-related genes?NYC1,CLH,PAO1?expression levels were down-regulated,while chlorophyll degradation-related genes?NOL,PPH,ACD2,NYE1,SGR?and antioxidant The expression levels of related genes?CuSOD,PGP?and redox-related genes?TRX-M1?were up-regulated;while antioxidant enzyme-related genes?MnSOD,FeSOD,CAT,2cprx,GR,PRX,APX?and redox-related genes?TRX-F,TRX-M2?The overall expression level was down-regulated.In summary,different concentrations of cadmium stress inhibited the normal growth of pea plants,but pea plants showed different physiological responses at different stages and were regulated by different mechanisms.