| Phosphorus,one of essential mineral nutrition elements for plant,is indispensable to plant growth and development.Low availability of phosphorus in the soil has become an important limiting factor for crop growth.Rapeseed(Brassica napus),one of the major oil crops in China,is sensitive to phosphorus deficiency.Thus,exploring rapeseed phosphorus efficient molecular and physiological mechanism for genetic improvement of rapeseed phosphorus efficiency and excavating phosphorus efficient genetic resources has important theoretical and practical significance.In this study,based on the public rapeseed genome database and the previous RNA-seq analysis in our lab,the characteristics of rapeseed LPR family genes homologous to Arabidopsis root architecture related genes LPR(Low Phosphate Root)was analized by using bioinformatics technique and qRT-PCR.Then the function of BnaA07LPR2 of the family genes was studied by overexpressing BnaA07LPR2 in Arabidopsis.The main results were as follows: 1.Growth and phosphorus uptake of plants under short-term P-free starvation and long-term low P stress in Brassica napusThe high efficient genotype “Eyou Changjia” was used as material,and nutrient solution cultures to set up short-term P-free starvation and long-term low P stress treatment were designed to analyse plant growth and phosphorus uptake in this study.When the phosphorus supply was sufficient,most of the uptaken phosphorus and photosynthetic products was used for the shoot vegetative growth,which showedlower root/shoot ratio.While the phosphorus supply was limitted,the root growth and development was first satisfied and the transport of phosphorus to the shoot were reduced,resulting in increased root/shoot ratio.In the two treatments,phosphorus utilization efficiency has been significantly improved,and the phosphorus use efficiency under phosphorus starvation condition was significantly higher than that under normal phosphorus.But the change of phosphorus use efficiency in root and shoot was different.The results show that the re-use of phosphorus in the plant increased,and there are distinct differences in the use and distribution of phosphorus in different parts of the same genotype.2.Characteristics of LPR family genes in Brassica napusUsing the gene information of LPR1 and LPR2 of Arabidopsis thaliana and the published genome sequence information of Brassica napus,four homologous genes BnaLPRs were identified in Brassica napus,which distribute in A07,A09,C05,C06 four chromosomes,respectively.Amino acid sequence similarity of the four BnaLPRs genes is in 77-99%,and nucleic acid sequence consistency is 36-95%.The amino acid sequence and nucleic acid sequence between BnaC06LPR2 and BnaA07LPR2 genes were the most consistent.BnaC06LPR2 and BnaA07LPR2 genes are similar,which have two introns and three exons,but is different from AtLPR2,indicating that BnaLPR2 s function were differentiated during the evolution of Brassica napus.Analysis of conserved domains showed that LPR gene family contains three mult-copper oxidase domain.Phylogenetic tree results further confirmed the reliability of gene structure and protein conserved domain analysis.3.The spatial and temporal expression patterns of LPR gene in response to low phosphorus stress in Brassica napusBased on the data of the rapeseed transcriptions under phosphorus deficiency in our laboratory,gene expression of three BnaLPR was detected,further qRT-PCR results showed that the induction had short-term persistence and had different responses to phosphorus starvation at different sites.The results of qRT-PCR in different tissues of Brassica napus showed that the gene function of BnaLPRs family in allotetraploid Brassica napus was differentiated with the long evolutionary process,which had different expression patterns indicating different effects and biological function in the phosphorus signal regulation.4.Preliminary analysis of the function of BnaA07LPR2 gene in Brassica napusUsing reverse genetics to study the functional differences of BnaLPRs in phosphorus signal regulation,construction of 35 S promoter connecting BnaA07LPR2 CDS overexpression vector was transformed into Arabidopsis thaliana(Col-0).Through agar and nutrient solution culture experiments,the growth of wild type(Col-0),lpr1 mutants and overexpressing BnaA07LPR2 transgenic Arabidopsis lines in different phosphorus and iron treatments was analysed.The results showed that phosphorus deficiency could inhibit the growth of primary root,and the primary root length under phosphorus deficiency was: lpr1 > OE-BnaA07LPR2 > Col-0.The relatived expression level of phosphorus starvation-induced genes in the transgenic line roots was significantly increased,indicating that BnaA07LPR2 may play a positive role in the regulation of phosphorus signal transduction pathway.Therefore,we speculate that BnaA07LPR2 gene and Arabidopsis LPR1 and LPR2 have functional differentiation,the overexpression of BnaA07LPR2 can alleviate the inhibition of the primary root growthunder phosphorus deficiency. |
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