Uptake And Distribution Of Kasugamycin In Ricinus Communis

Agricultural antibiotic fungicide,aminoglycoside antibiotic kasugamycin is widely used in the management of plant diseases such as rice blast.Studying its uptake mechanism,translocation and distribution in plants has important significance for the development of pesticides that can be transport to the roots and the management of pests in the roots and stems.Castor,classic model plant of phloem transduction was studied in this paper to explore the uptake mechanism of kasugamycin;a fluorescently labeled kasugamycin was synthesized to trace the translocation of kasugamycin in castor,tobacco and corn.The main results are as follows.1.High performance liquid chromatography-mass spectrometry(HPLC-MS/MS)was used to detect phloem exudate from castor,the results show that: the uptake of kasugamycin conforms to the enzymatic reaction Michaelis-Menten kinetic model,kinetics.The parameters are : Km=1.705 m M,Vmax=2.752 nmol/m L/h;at the same time,the uptake is sensitive to temperature and pH,and the uptake at low temperature(4℃)is only 29.40% that of under normal conditions;the maximum uptake is at pH 5.5,390.76±31.69 μg/L,the uptake at pH9.0 is only 36.90% of pH 5.5;the energy inhibitors dinitrophenol(DNP)and carbonyl cyanide chlorophenylhydrazone(CCCP)can lead to a reduction in the uptake of kasugamycin by 34.22% and 47.85%,respectively.Competitive substrate D-glucose and monosaccharide inhibitor phlorizin can inhibit the uptake of kasugamycin by castor,40.00 mmol/L D-glucose,the inhibition rate is 45.07%,and the inhibition of 1.00 mmol/L phlorizin is 54.32%.All results indicate that the uptake of kasugamycin is an active uptake process mediated by monosaccharide transporters.2.To trace the distribution and conduction of kasugamycin in plants,a nitrobenzo-2-oxa-1,3-diazole(Nitrobenz-2-oxa-1,3-diazole,NBD-Cl)fluorescently labeled Kasugamycin(KSM-NBD).The maximum excitation wavelength of the KSM-NBD is 453 nm,the emission wavelength is 521 nm,and the uptake of the castor-absorbing fluorescent coupling compound KSM-NBD at pH=5.5 is 0.61 mg/L.The uptake capacity is affected by temperature,and the uptake capacity under 4℃ is only 42.33% of the control group;the energy inhibitor DNP and CCCP inhibit the uptake rate of KSM-NBD by 45.84% and 57.20%,respectively;adding a competitive substrate after glucose and glucose transporter inhibitor phlorizin,the uptake was only 50.78% and 59.13% of the control group.The above results show that the fluorescent compound and kasugamycin have the same uptake characteristics and can be used to trace the distribution of kasugamycin.3.Using HPLC-MS/MS and fluorescence tracer method to study the distribution of kasugamycin in plants.Middle leaves of castor,tobacco and corn were soaked in the kasugamycin.After 24 hours,untreated apical leaves,stems and roots were all detected with kasugamycin,and the content increased with time.Among them,the content of kasugamycin in the roots was higher than other parts.In the roots of castor bean,the contents in the two periods of 24 h and 48 h were 1.52 and 3.20 μg/g,respectively;in the roots of tobacco,the contents in the two periods were 1.67 and 2.21 μg/g;in the roots of corn,the contents of the two periods The contents were 0.97 and 1.63 μg/g,respectively.It shows that it can be transported bidirectionally in castor,tobacco and corn plants.KSM-NBD fluorescent conjugates are mainly distributed in mesophyll cells and phloem and xylem in castor;in tobacco,they are located in xylem,duct,phloem and sieve tube;in corn,they are distributed in the vascular bundle of leaf vein In the phloem,xylem and parenchyma of the stem,it indicates that the kasugamycin mainly conducts bidirectional transmission through the xylem and phloem.The research shows that the uptake of kasugamycin by plants is closely related to the electrochemical potential gradient,energy and monosaccharide transport protein across the plasma membrane,and is an active transport process.It can be transported bidirectionally through xylem and phloem,mainly distributed in cotyledon mesophyll cells,xylem,phloem and sieve tubes and ducts.Further research on the structure-activity relationship between the uptake and translocation of kasugamycin and the chemical structure is of great guiding significance for the design and synthesis of pesticides with bidirectional translocation.