The Evolution And Functional Diversification Of AOX Gene Family In Populus Euphratica And P.Pruinosa

Gene duplication is widely present in organism genome, and plays an important role in evolution for providing raw material for functional innovation. Gene family is believed to be one of products of gene duplication. The research on history and adaptive on gene family evolution, not only helps to clarify the mechanism of speciation and adaptation, but also provide the important genetic resource for mechanisms of plants stress.In this study,102A OX sequences were collected from genome data of bacterial, lower animals, liverworts, gymnosperm, angiosperm ancestor, monocots and dicots. We constructed phylogenic tree to survey the he evolution history of AOX gene family. The result indicated that AOXgenes were originated from bacterial, and then imported into the ancestor of eukaryotes from the endosymbiosis of bacterial. Only some lower animals had AOX genes. It seem that the AOX genes were lost in other animals. In addition to animals, we only found one AOX1copy in liverworts and gymnosperm. The diversification of AOX1and AOX2occurred in the ancestor of angiosperm. Along with the evolution of the angiosperm, the monocots lost AOX2subfamily genes, while this was only happened in Populus genus in dicots specially. So we propose that the loss of A OX2were directly link to the diversification of AOX genes in Populus genus.To examine the A OX gene family diversification in P. euphratica and P. pruinosa, we measure the alternative pathway and its molecular response to M. pruinosae infection. The results indicated a less decline in the net photosynthesis, stomatal conductance and a lower content in H₂O₂in P. pruinosa, meant the P. pruinosa was more resistance to the M. pruinosae. The proportion of alternative respiration （Valt） in all respiration was higher in P. pruinosa （P<0.05）, which indicated the P. pruinosa could protect the cell against with the H₂O₂through activating the alternative respiration pathway faster. All above showed that the P. pruinosa was more resistance to M. pruinosae and it was directly related to the alternative respiration pathway.We found that AOXla and AOXld had the same expression pattern in these two species, but the AOXlb and AOXlc were different in different grades of rust infection （P<0.05） though RT-PCR methods. We used the whole genome resequence data of P. euphratica and P. pruinosa populations and found that the diversification of in the promoter sequence of AOXlb and AOXlc is much higher than the protein coding sequence between these two species, but the decay that of in linkage disequilibrium of AOXlb and AOXlc promoter sequence was different between these two species. So we propose the difference of the rust resistance between P. euphratica and P. pruinosa would be mainly caused by the population demography or the positive selection.