Analyzing On The Tolerance And Related Genes To Low-Phosphate Stress In Mulberry(Morus Multicaulis)

As the second largest nutrient necessary for the growth and development of the plant,the absence of phosphorus will inevitably cause the plant to produce a series of response reactions,which are collectively referred to as the low-phosphorus response.Phosphate transporter low-phosphate-induced expression is an important response mechanism for plants to cope with phosphorus stress.Among all phosphate transporters,the PHT1 family transporter,which is mainly expressed in the root,is most directly affected.In addition,when plants face low-phosphate stress,their physiological and biochemical activities will also respond accordingly.For example,changes in root morphology and changes in endogenous protective enzyme activities are all necessary measures for plants to adapt to low-phosphorus environments.In order to study the effects of low-phosphorus environment on mulberry trees,we started with the Phosphate transporter genes of Morus multicaulis,and selecting the double-affinity MaPHT1;4 gene,the high-affinity MaPHT1;7 gene and the low-affinity MaPHT1;9 genes as the research objects.In this study,cloning technology was used to obtain the DNA sequences of these three phosphate transporter genes.The structure and homology of the three sequences were analyzed using a variety of bioinformatics methods;then real-time PCR were used to analyze the three phosphate genes expression patterns under four Pi levels of P40,P20,P10,and P0;According to the results of the low-phosphate marker gene MaPHT1;4 expression levels under low phosphate(P10)and non phosphate(P0)stress,combining with the results of mulberry trees physiological and biochemical responses to low Pi stress,we determined the timing of the low-phosphate transcriptome of mulberry trees;Then analyzed and validated the transcriptome results,and explored the transcriptional regulation mechanism response to low-phosphate stress of mulberry.The main results of this study as followings:1.The MaPHT1 gene in mulberry tree is very conservative.The structural analysis of the nucleic acid and amino acid sequence of three mulberry MaPH1 genes showed that the DNA sequence length,protein size,and higher-order knot structure all have great similarities.Homology analysis showed that MaPHT1 is homologous to PHT1 of other plant species.The similarity is very high,especially compared to Morus notabilis,which is as high as 98%.2.Phosphorus stress induces MaPH1 gene expression in mulberry trees.The results of MaPH1 gene expression analysis under different phosphorus levels showed that the expression levels of MaPHT1;4 and MaPHT1;7 genes induced by low-phosphorus were significantly higher than MaPHT1;9 genes induced by high-phosphorus conditions.3.The mulberry shows some stress resistance under low phosphate stress.Physiological and biochemical experiments under low-phosphate stress showed that the activity of protective enzymes in mulberry leaves varied greatly,and the morphological structure of the roots also changed.Those were directly prove that mulberry trees have resistance to low phosphate stress.4.Mulberry responds to low-phosphate stress through positive and negative transcriptional regulation.In the transcriptome data,the up-regulated and down-regulated differential genes have a wide range of biological pathways,and it is right through these ways which the transcriptional regulation of these genes that plants respond to low-phosphorus stress.