The Effect Of Two Defence Signaling Substances On The Salivary Gland Gene Expression Of Myzus Perisicae

The green peach aphid is an important agricultural pest, they can destroy crops by direct feeding or indirectly virus transmission. The relationship between aphid and plant is very complex after a long time co-evolution. The plant defense responses can be induced by aphid infection, and this kind of response can direct inhibit the feeding of aphid, or attracting the aphid nature enemies. The most important signaling pathways are SA and JA. When the aphid feels the response of plant defense, they can adapt to it by secreting more saliva, and change the phloem sap to its favorite nutrition.In this study, we use the green peach aphid from Beijing and Shandong as the object. At first, we determine the threshold concentration of two plant signaling pathway which the green peach aphid can adapt to. After feeding the aphid with artificial diet contains SA or JA, we collect the aphid on different time, and then determine the expression level of three genes: Mp10、Mp42and MpC002, which has been proved to be the candidate effectors. We confirmed the gene expression change under the pressure of SA or JA. And it can provide a theoretical and research basis for elucidating the interaction between aphid and plant.1The determination of the threshold concentration of plant defense signaling substancesAt first, fed the green peach aphid with the diet which contains SA or JA in different concentrations, and then determined the survival rate, used the artificial diet as the control, to make sure the threshold concentration of plant defense signaling substances. We also used the density on the plant to make the result better. The result showed that the green peach aphid can adapt to the diet with10mM SA or5mM JA, and there was no difference between Beijing and Shandong. And also, the death rate of the second day was significantly higher than the first day, especially feeding on the higher concentration.2The multiple result of three gene sequencesWe cloned and sequenced the three genes which were only expressed in the salivary gland, and then compared them with the sequence in the GenBank. The result showed that, there were some mutations of individual bases in each sequence, but it was not significant. And for the MpC002gene, there was only one base mutation in the green peach aphid from Shandong. It meaned that this gene is very important for the aphid. 3The changes of the three genes after feeding the green peach aphid with different objectsWe fed the aphid with SA or JA, the artificial diet as the control, collected the aphid on different times. And then, used the qPCR to determine the changes of the three genes. The results showed like that:When the green peach aphid was fed on the artificial diet, SA, and JA, the change of Mp10and MpC002genes expression were basically the same:it should be significantly improved during a short time, after a certain degree of decline, then rise again. But for the JA, when the Mp10gene expression level declined, the time should be longer of the aphid from Beijing than the Shandong group. It was visible that, the green peach aphid could adapt to the poor food with over expression of Mp10gene. And it should be different between the two group populations. And the expression of MpC002gene should continue to rise for all the time. It meaned that, aphid could adapt to the poor food by over expression of MpC002gene. And also, this protein should play an important role in the aphid adaptation to the plant induced defense.But for the Mp42, the expression level was opposite. When feeding on the artificial diet or S A, the expression level of Mp42gene should be significantly reduced during a short time, the minimum value should be at6h, and then rebounded. The Mp42gene expression level of the aphid from Beijing was significantly lower than the Shandong group. But for the JA, after the significantly reduce, it should rebound slightly, and then continue to decline. It showed that, the aphid could adapt to the poor food with reducing the expression of Mp2gene. Maybe the expression of Mp42gene should consume excessive resources, or the secretion of this protein into plant phloem can induce the defense response. And the Beijing group was more sensitive.In this result, we can see that, the change of each gene is always the same when they fed on the artificial diet or SA, but for the JA, it is quite different with the control. It also shows that, JA plays an more important role in plant resistance to the aphid infection.