Interactions Between TDIF Peptide And Auxin In Regulating Arabidopsis Root Development

Tracheary element differentiation inhibitory factor(TDIF)plays an important role in mediating cell–cell communication and stem cell maintenance during plant development of vascular tissue.Meanwhile,TDIF was also linked to lateral root(LR)organogenesis through the action of Brassinosteroid Insensitive 2(BIN2)to directly phosphorylate and enhance the transcriptional activity of Auxin Response Factors(ARFs).In order to explore the interactions between TDIF peptide and auxin in root development of Arabidopsis thaliana.The effects of TDIF on the growth of primary root(PR)and LR of Arabidopsis thaliana were studied using two experimental techniques of exogenous addition of TDIF peptide(TDIF peptide encoded by At CLE41 and poplar Pt TDIF2,TDIFL peptide encoded by poplar Pt TDIFL1)and overexpression of TDIF and TDIFL genes.The results demonstrated that the two TDIF peptides could promote the PR elongation and stimulated the LR for mation to a varying degree.Without affecting the auxin biosynthesis and catabolism in the root of Arabidopsis thaliana,TDIF could inhibit auxin accumulation at the quiescent center(QC)but increase auxin accumulation at the formation site of LR to promote LR formation.The sur2 and taa1 mutants responded to TDIF-like in a same trend as wild-type plants,although to a lesser degree,demonstrating that a certain level of endogenous IAA might be required by the plants to fully respond to TDIFL.Meanwhile,TDIF could specifically up-regulate the transcriptional level of all members of PINs(PIN1-8)gene in Arabidopsis thaliana roots and NPA could completely blocked the enhancing effect of TDIF on root growth.Meanwhile,the pin1,pin2,pin3 and pin7 mutants displayed insensitivity or low sensitivity to TDIFL.These results together demonstrated that PIN-mediated polar auxin transport(PAT)is indispensably required for the TDIF-induced root phenotypes.In summary,this work clarified that TDIF regulated the accumulation and distribution of auxin in primary root and lateral root by up-regulating the expression of PIN transporter gene and hence facilitate PR elongation and LR formation.This study revealed the interaction between TDIF and auxin two hormone signaling molecules in the root development of Arabidopsis thaliana and further explained the molecular mechanism of root response to TDIF and auxin.