Involvement Of PIP3 And PIP2 In The Regulation Of Auxin Response And Plant Growth And Development In Arabidopsis

Plant hormone auxin plays an important role in the regulation of plant growth and development.Some of the functions of auxin in regulating plant growth and development are similar to that of some peptide hormones.However,the relationship between auxin and peptides is not well understood.It has been reported that several member of the recently identified of PAMP-induced secreted peptide(PIPs)and PIP-LIKE peptide(PIPL)family are involved in the regulation of innate immune responses as well as biotic and abiotic stress tolerance in Arabidopsis.Here we report the identification of two members of PIP/PIPL family genes,PIP3(At2g23270)and PIP2(At4g37290)as auxin response genes,and that PIP3 and PIP2 are involved in the regulation of plant growth and development.RT-PCR analyses showed that PIP3 and PIP2 were induced by exogenously applied IAA(Indole-3-acetic acid),a naturally occurred auxin.Protoplast transfection assays showed that PIP3 and PIP2 were not localized in a particular cell organelle.Phenotypic analysis showed that plants overexpressing PIP3 and PIP2 produced epinastic type of leaves and have shorter root when compared to Col wild type.The single mutant pip2 also produced shorter root.Transgenic plants overexpressing PIP3 showed enhanced tolerance to auxin in primary root elongation assays.Further analyses showed that PIP3 and PIP2 expression were hyposensitive and hypersensitive to auxin in hypocotyl elongation and lateral root formation respectively compared to Col wild type plants.As a whole,our result showed that PIP3 and PIP2 are auxin responsive peptide hormone genes that involved in the regulation of auxin response and plant growth and development in Arabidopsis.