Ectopic Overexpression of an AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) Gene OsIAA4 in Rice Induces Morphological Changes and Reduces Responsiveness to Auxin

Yaling Song,Zeng-Fu Xu

doi:10.3390/ijms140713645

Abstract

Auxin has pleiotropic effects on plant growth and development. AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) proteins are short-lived transcriptional regulators that mediate auxin responses through interaction with an auxin receptor, the F-box protein transport inhibitor response 1 (TIR1). Most functions of Aux/IAA proteins have been identified in Arabidopsis by studying the gain-of-function mutants in domain II. In this study, we isolated and identified an Aux/IAA protein gene from rice, OsIAA4, whose protein contains a dominant mutation-type domain II. OsIAA4 has very low expression in the entire life cycle of rice. OsIAA4-overexpressing rice plants show dwarfism, increased tiller angles, reduced gravity response, and are less sensitive to synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-D).

Highlights

It is known that auxin plays a very important role in a wide variety of plant developmental and physiological processes [1]
OsIAA4 and OsIAA8 belong to one category with the expression level undetectable in almost all the organs/tissues [22]
OsIAA gene family shows OsIAA4, OsIAA8, and OsIAA10 belong to one subclade, of which no further investigation into their functions have been reported (Figure 1a)

Summary

Introduction

It is known that auxin plays a very important role in a wide variety of plant developmental and physiological processes [1]. Several genes involved in the regulation of auxin dependent transcription have been identified, and of this Aux/IAA protein family members have been studied most thoroughly. Aux/IAAs are short-lived transcription factors comprising four highly conserved domains, known as. 2013, 14 domain I, II, III, and IV. Domain I contains conserved motif “LxLxL” and acts as a strong transcriptional repressor [2]. Domain II contains a core sequence “GWPPV” responsible for the rapid degradation of Aux/IAA proteins by interacting with a component of the ubiquitin-proteasome protein degradation pathway, which is stimulated by auxin [3,4]. Domains III and IV, shared by ARF proteins and Aux/IAA proteins, mediate homo- and hetero-dimerization among members of these two protein families [5,6]

Methods

Results

Conclusion