The Structure Of Compound Eye And Function Of Opsin Of The Asian Citrus Psyllid(Diaphorina Citri Kuwayama)

The Asian citrus psyllid,Diaphorina citri Kuwayama(Hemiptera: Liviidae)is the main vector of the Candidantus Liberibacter asiaticus,which causes the citrus huanglongbing(HLB)disease.It was regarded as the most important pest of citrus orchard because the huanglongbing have caused dramatic losses.No effective measure have been found for the prevention of citrus from infection by the HLB.Control of the population of the citrus psyllid is an important measure to inhibit the spread of the disease.It is necessary to search an effective and environmental-friendly approach for the control of citrus psyllid.Present study aims at the phototaxis,the compound eye morphology and opsin function of the Asian citrus psyllid,attempting to obtain scientific information about the vision of the insects.The main results of this research are as fellows:(1)The phototoxic rate on five different LED-ultraviolet(365-370 nm),blue(470-475 nm),green(520-525 nm),red(620-630 nm)and yellow(590-592)with the controal of white lamp showed that the highest phototaxis is ultraviolet and the the descending order was listed: blue,green,yellow and red.The citrus psyllid phototaxis between ultraviolet and blue is significant difference than that of the control group.(2)The external structure of the compound eyes was observed by using the scanning electron microscopy.The results showed that the ACP compound eyes were situated on the both sides of the head and their shape is hemispherical.No obvious difference can be seen in the external structure of male and female compound eyes of ACP.The number of the ommatidia which is the component of the compound eye is different.The male and female ACP have approximately 225-254 and 238-252 ommatidias,respectively.The external structure of the ommatidia a have a little different change with the location changing.The ommatidia in the central region have a regular hexagon as they are lining closely,while those in the outmost were round as they were not close.The outline of the compound eye is very smooth with no attachments.(3)Preliminary study the internal structure of the compound eye.Optical microscope and scanning electron were used to achieve the picture.The ommatidia was compound by the cornea,crystalline cone,rhabdom,retinula cell and basement membrane.The cornea is located the outside of the ommatidia and formed by the layered structure.The crystalline cone directly connecting the rhabdom,it shows that the model of the compound eye belongs the opposition eye.The crystalline cone and the rhabdom were surrounded by the pigment cells.It play an important role in adapting the change in the light intensity by moving.In the condition of the light,the pigment cell evenly distributed around the crystalline cone and the rhabdom.But in the dark condition,the pigment cell the move to the distal end and the proximal of the ommatidia.(4)By observing the brain structure of the ACP,the results showed that the optic lobe was composed by the lamina,medulla,lobula complex.Serotonin is mainly distributed in the third layer of the medulla and the lamina.(5)The physical properties was obtain by analyzing of the opsin sequences of ACP.We filer the opsin gene from the transcriptome data and designed the primers in the outside of the open reading frame.We have use the blast to confirm the opsin gene.The five opsin sequence named Opsin,Long,Blue,Uv and Melon,have 1146,1555,1134,1635 and 1470 bp,respectively.All the opsin have seven membrane-spanning helical domains.Long,Blue and Uv have two functional sites,which were the G-protein coupled receptor family and the opsin retina binding site.Opsin has the retinal binding site.Melon has only a family of G protein-coupled receptors.(6)We explore the trend of the opsin expression in the circadian rhythm and different age of ACP.The results show that the relative expression of the opsin of the nymph is lower than the adult.In the circadian rhythm,the expression level of Opsin expression was highest in male ACP at ZT4-ZT7 and the peak expression of Long and Blue was ZT7.For the female ACP,Opsin's expression peak was in ZT5 and Long and Blue reached the highest expression level at ZT8.(7)The function of opsin was evidenced by using the method which the dsRNA was used to feed the ACP.The conclusion is that dsOpsin and dsLong inhibited the expression of Opsin and Long opsin by 64.60% and 18.15% after treated and the phototactic to Uv and the green light decreased by 46.73% and 54.81% after Opsin and Long knockdown,respectively.The Opsin and Long contributes to phototaxis and increases phototactic efficiency to ultraviolet and green light.