| In order to elucidate the role of Buchnera in the aphid adaptation to host plants,we studied the growth and development,the contents of the substance in the body of symbiotic and de-symbiotic pea aphids,and the relative expression changed of Buchnera's 16 S r RNA,on six common host plants.The following main results were obtained:1.Effects of temperatures on the body length,symbiotic bacteria's abundance and size of Pea aphid To explore the effect of temperatures on the endosymbiotic bacteria in pea aphids and size of their hosts,the changes in the abundance and size of mycetocytes and host body size under different temperatures(16?-32?)were observed.The results showed that the number of symbiotic bacteria increased first and then decreased with increasing temperature,the highest number of symbiotic bacteria at 28 ?,red and green morph of pea aphids were 121.38 and 99.48 respectively,and the number of symbiotic bacteria was significantly decreased at 32 ?,compared with the red and green pea aphids at 28 ? reduced 44.64% and 58.16%.These data indicate that high temperature has a certain inhibitory effect on the number of symbiotic bacteria in pea aphids,and red morph of pea aphids are more adaptable to the changing of environment.At 25 ?,28 ?,32 ?,the diameter of symbiotic bacteria was greater than that of 16 ?,19 ?,22 ?,and the number and diameter of bacteria were no correlation.The body size of pea aphid increased first and then decreased with the increase of temperature,the maximum appeared at 22 ?.Under the relatively low temperature of 16 ? and high temperature of 28 ?,the number of bacteria was' t linear correlated with the size of the body,but it showed a good linear correlation at 23 ?,22 ? and 25 ?,which is the suitable temperature of pea aphid growth.While did't show a correlation at 32 ?.2.Effects of symbiotic bacteria on the growth and development of pea aphid ondifferent host plants The results of symbiotic and de-symbiotic pea aphids were reared on six common host plants(Vicia faba,Pisum sativum,Medicago sativa,Trifolium pretense,Melilotus officinalis,Onobrychis viciaefolia)showed that the growth period of the nymphs was prolonged,the adult stage was shortened,the survival rate of the nymph decreased and the body weight decreased,which compared with the symbiotic pea aphids.In different host plants,the de-symbiotic pea aphids compared with symbiotic pea aphids at the same color morph: the growth period of red and green morphs of pea aphid on Onobrychis viciaefolia was the longest and prolonged 2.9 and 2.82 times respectively,and the shortest time on the Trifolium pretense was 1.36 and 1.64 times;The life span of adults on Melilotus officinalis was the shortest,and the red and green morph were shortened by 38% and 44.8% respectively;The nymphal survival rate on Pisum sativum was significantly higher than that of Medicago sativa and Onobrychis viciaefolia;The weight loss rate of red and green morphs of pea aphid was higher on Vicia faba,decreased by 78.53% and 72.20% respectively,and lower on Medicago sativa decreased by 64.06% and 58.14% respectively.In conclusion,the presence of pea aphid symbiotic bacteria has a beneficial effect on the growth and development of host aphids,and there are differences between host plants.3.Effects of symbiotic bacteria on the matter content in the body of pea aphids under different host plants After the Symbiotic and de-symbiotic pea aphid feeding with different host plants,the de-symbiotic pea aphid's protein content was lower than the same color morph of symbiotic pea aphid 21.06%-56.42%,the lowest on Medicago sativa and the lowest rate of decline on Onobrychis viciaefolia.The de-symbiotic pea aphid's soluble sugar was lower than the same color morph of symbiotic pea aphid 27%-76.37%,the lowest in Medicago sativa,and the lowest rate of decline on Melilotus officinalis.The de-symbiotic pea aphid's glycogen was lower than the same color morph of symbiotic pea aphid 25.08%-70.28%,the lowest in Medicago sativa,and the lowest rate of decline in Onobrychis viciaefolia.In addition to the total fat content of green morph of de-symbiotic pea aphid was lower than the symbiotic pea aphid,which was feeding on Medicago sativa and Onobrychis viciaefolia respectively,the total fat content of two morphs of de-symbiotic pea aphid is higher than the same color morph of symbiotic pea aphid.From the above,the content of protein content,soluble sugar and glycogen of pea aphid was cut down,and the total fat content showed an upward trend,after taking off the symbiotic in pea aphid.4.Expression analysis of symbiotic bacteria 16 S r RNA in pea aphid after being fed on different host plants After being fed on different host plants(Pisum sativum,Medicago sativa,Onobrychis viciaefolia,Trifolium pretense,Melilotus officinalis),the relative expression of symbiotic bacteria 16 S r RNA gene was significantly up-regulated in two morphs of pea aphid.In the red morph,the relative expression of Buchnera's 16 S r RNA was significantly different from that in the other host plants,except in being fed on Medicago sativa and Melilotus officinalis.In the green morph,the relative expression of Buchnera's 16 S r RNA in being fed on Onobrychis viciaefolia was significantly higher than that on Medicago sativa,Melilotus officinalis and Pisum sativum,and significantly lower than that of Trifolium pretense.And the Buchnera's 16 S r RNA in two morphs of pea aphid was higher on Trifolium pretense,and the relative expression was lower on Pisum sativum.Under the same host plant,different color morphs of pea aphid.The relative expression of Buchnera's 16 S r RNA in the red morph of pea aphid was higher than that in the green morph of pea aphid,which indicated that red morph of pea aphid was more adaptable to host plants. |
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