Abstract:

Abscisic acid (ABA) is an important plant hormone, which can control seed and bud dormancy, organ size control, senescence and death, and participate in both biological and abiotic stress, inhibit plant growth, and participate in plant disease resistance. In order to determine the content of ABA in plants quickly and accurately, a new type of ABA immunosensor was developed. To improve the detection performance of the sensor, the detection performance of the sensor was increased by modifying GR-COOH and SA on the electrode surface. The concentration of GR-COOH, SA, and ABA-Antibody were optimized, the optimal conditions for the three materials were 1.5 mg/ml, 1.25 mg/ml and 0.5 mg/ml. The immunosensor was constructed based on the electrode impedance changes (△Z )_{due to the binding reaction of ABA antibody and antigen. It was found that the sensor showed linear relationship with ABA in the response range of 10 pmol/L~1 μmol/L, R² was 0.99927, and the detection limit was about 10 pmol/L. The sensor also had good selectivity and stability. Using the electrochemical immunosensor, the content of ABA in navel orange leaf that have been successfully inoculated with citrus Huanglongbing by PCR was determined, and healthy plants were used as control. The test results showed that the impedance changes(△Z ) of healthy leaves and diseased leaves were 72 and 823, respectively, which indicated that the level of ABA in the infected plants increased significantly. The sensor provides a tool for the detection of plant hormone levels under disease stress. The results showed that the content of ABA increased in the leaves of navel orange infected by citrus Huanglongbing, which indicated that ABA played an important role in plant disease resistance. Furthermore, the changes of gene expression of key enzymes CitZEP in ABA synthesis pathway were studied, The results showed that the expression of CitZEP increased in plants infected with Huanglongbing disease, and the results were consistent with the detection results of the sensor, which indicated that the sensor had good practicability.}

Key words: abscisic acid, immunesensor, electrochemical, Huanglongbing, GR-COOH, antibody