Analysis Of Metabolic And Phosphatase Gene Expression Profile In Cajanus Cajan Roots Under Low Phosphorus Stress

Pigeon pea(Cajanus cajan)is the only woody edible bean crop among the six edible legumes,with an annual global output of about 4.49 million tons.and widely planted in tropical and subtropical regions of the world.Pigeon pea has a wide range of uses,green seeds can be used as vegetables,dry ripe seeds are edible,leaves with medicinal value can also be used as forage and green fertilizer.In addition,pigeon pea is also used as a pioneer crop for vegetation restoration,soil and water conservation,barren mountain greening,due to the developed roots,high nitrogen fixation efficiency,strong resistance of drought and barren.Previous studies have shown that pigeon pea had strong adaptability to aphosphagenic acid soil,but the potential mechanism of adapting to phosphorus deficiency is still unclear.In this study,the response mechanism of pigeon pea roots on low phosphorus stress was analyzed using the metabolomics and transcriptome technology with pigeon pea ICPH2740 as study material,the main research results were as follows:(1)The dry weight and total phosphorus content of pigeon pea were significantly reduced under phosphorus limitation stress,but the activity of antioxidant enzymes(superoxide dismutase,peroxidase)and the content of antioxidant substances(ascorbic acid,total phenols,total flavonoids)in roots were markedly increased,which indicated that pigeon pea might resist the damage of root system under phosphorus insufficient stress mainly depending on improving the antioxidant capacity.(2)A total of 558 metabolites divided into 14 categories were identified by metabolomics analysis in pigeon pea roots.Among them,166 metabolites were defined as differential metabolites under phosphorus sufficient and deficient treatments,which mainly belonged to nucleotides and its derivatives,lipids,amino acids and its derivatives.(3)The content of phosphate-containing metabolites were significantly decreased in pigeon pea roots under phosphorus limitation treatment,including 20 phospholipids(namely 13 LysoPC,5 LysoPE,glycero-3-phosphocholine,2-aminoethyIphosphonate),9 kinds of nucleotides and its derivatives containing phosphorus(namely cyclic AMP,guanosine 3’,5’-cyclic monophosphate,uridine 5’-diphospho-D-glucose,flavin adenine dinucleotide,uridine 5’-diphosphoglucose disodium salt,uridine 5’-monophosphate.UDP-α-D-glucose,NADP,adenosine 5’-monophosphate),4 kinds of phosphorylated sugars(namely glucose 6-phosphatc,glucose-1-phosphate,fructose 6-phosphate,ribulose-5-phosphate).The relative contents of glycero-3-phosphocholinc,cyclic AMP and guanosine 3’,5’-cyclic monophosphate were markedly reduced by more than 20 folds under low phosphorus stress.(4)A total of 146 phosphoesterase encoding genes divided into 15 categories were identified in pigeon pea roots by transcriptome analysis.Among them,purple acid phosphatase(CcPAP)family had the most members,up to 26 genes,and 14 genes of them were up-regulated expression by low phosphorus induction.In addition,the families of phospholipase gene participating in phospholipid degradation including phospholipase C(CcPLCO,phospholipase D(CcPLD),phosphatidylphosphatase(CcPAH),phosphoethanolamine/choline phosphatase(CcPECP)and glycerol phosphodiesterase(CcGDPD)were enhanced expression under phosphorus limitation,which contained four,two,one,three and two genes.respectively.The families of phosphoesterase gene involved in nucleotide degradation were induced up-regulation expression by low phosphorus stress,including ribonuclease T2(CcRNS),exonuclease and endonuclease,in which identified two,four and three genes,respectively.Finally.there were one,one,two genes belonged to the family of phosphosugar phosphatase(CcSgpp),sucrose 6-phosphophosphatase(CcSPP)and soluble non-mechanical pyrophosphatase(CcPPase),respectively,which all were induced up-regulation expression by phosphorus limitation and involved in the degradation of phosphorylated sugars.In Conclusion,pigeon pea can enhance the transcriptional expression of phosphoesterase related coding genes,to promote the reactivation and utilization of phosphate-containing metabolites in vivo,and enhance the adaptability of pigeon pea to low phosphorus stress,when subjected to low phosphorus stress.