| The plant hormone auxin mediates numerous aspects of plant growth and development,including apical dominance, vascular tissue differentiation, lateral root formation, andtropisms like gravitropism and phototropism. PIN proteins also plays an important role in thelife of plant. The PIN family act as auxin efflux carriers playing important role during polarauxin transport.The subcellular localization of PIN proteins determinates auxin direction flowand unsymmetrical distribution in cells.The auxin accumulation on inoculation points is necessary for the formation of nodules.Suitable auxin concentration and auxin action are essential for the growth of nodules. Thereare different auxin responsees between the determinate and indeterminate nodulatingformation. Silence the related MtPINs displays a reduced number of nodules. Noduledevelopment progression needs the functional auxin transport systems. However, theinformation on the molecular mechanism of interaction between plants and microorganismsdirectly affects host plant auxin transport is very limited. Therefore, understanding auxincorrect location, transportion and accumulation, regulation of polar auxin transport duringnodule formation can provide a new way on auxin dynamic distribution. Understanding howPIN1is be regulated and localized gives us a breakthrough about the relationship betweenauxin and nodule formation, growth and developmental.The mutant uml with a reduced number of root nodules after rizobium inoculation resultsfrom auxin efflux carriers PIN1mututation. By analysising uml mutants we can furtherunderstand the relationship between auxin and nodule development.(1) uml mutants form the reduced number of nodules. In parallel, the main roots and thenumber of lateral roots of uml mutants are decreased.These data suggest that PIN1playsimportant role in nodule development.(2) Nitrogenase activity of uml is decreased more significantly than that of the wild type plants detected by acetylene reduction method.(3) The fusion of of PIN1promoter to GUS was introduced into Lotus japonicus by hairroot transformation to analyze PIN1gene spatial expression pattern in root nodules. GUSstaining showed that PIN1promoter is expressed in steles of uninoculated and inoculatedroots. But the expression in root tip is different. In uninoculated roots, Only partial cells haveGUS expression, while in inoculated roots whole root tips have GUS expression.Also,GUSstaining was detected in nodules.(4) The fusion of35S promoter to PIN cDNA was introduced into Lotus japonicus byhair root transformation to analyze complementation in uml. The result showed that thetransgenic plants containing PIN1gene can make uml mutants recover nodulation number ofwild type plants, suggesting that uml symbiotic is due to mutation of PIN1gene.(5) uml mutants are sensitive to auxin, but are unsensitive to auxin inhibitors.(6) Hairy root transformation of auxin response elements DR5::GUS reporter gene,GUS staining showed that different DR5activities were observed in different stages ofnodules. |
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