Primary Research Of The EXO70B Family Protein Regulate Polar Auxin Transport In Arabidopsis

The plant hormone auxin,is a key regulator of virtually every aspect of plant growth and development.Polarized auxin transport is mediated by PIN auxin efflux carriers,polarly localized at the plasma membrane.Auxin regulates transcription by rapidly modulating levels of Aux/IAA proteins throughout development.Exocytosis is a very important process in the plant is assisted by the exocyst.The complex consists of eight subunits,which include EXO70.EXO70 include 23 genes in Arabidopsis.We get a T-DNA loss functional mutant exo70B1-3.The mutant transcriptional level is decreased obviously by detecting the mutants mRNA.The exo70B1-3 mutants have obvious phenotype in Arabidopsis.The number of lateral roots is more in the mutants seedlings.The transcriptional level of LOB,which is expressed at the base of all lateral organs and mediates the response to auxin increase obviously in mutants.Rosette leaves of the mutants are smaller and more yellow.The gravitropism of the exo70B1-3 mutants accelerate.In the treatment expreriment with the different concentrations of NAA,the inhibition rate of primary roots lift in mutants,meanwhile LOB transcriptional level occur disorder obviously compared with the wild type.The DR5::GFP level significantly enhanced in mutants,which suggests auxin may occurs disorder in mutants.PIN2 is the auxin efflux carriers,which polarly localized at the plasma membrane.The recycling of PIN2 is delayed in exo70B1-3 mutant plants.It may indicate that the exo70B1-3mutants affect polarly location of PIN,then affect auxin transcription regulation,and affect the growth and development of plants.By yeast two-hybrid analyses,we find that the interaction beteen EXO70B1,EXO70B2 with Aux/IAA,which include IAA2,IAA5,IAA17,IAA18.Through protein truncated further found EXO70B1,EXO70B2 can interact with the domain IV of Aux/IAAs and Aux/IAAs interact with the N-terminal of EXO70B1.By GUS staining we find the tissue specificities of EXO70B1,EXO70B2 and IAA5 are similar,which further enhance the possibility of interactions between them.Further validation by LUC fluorescence protein prove interaction relations.