A gain-of-function mutation in IAA16 confers reduced responses to auxin and abscisic acid and impedes plant growth and fertility

Abstract

Auxin regulates many aspects of plant development, in part, through degradation of the Aux/IAA family of transcriptional repressors. Consequently, stabilizing mutations in several Aux/IAA proteins confer reduced auxin responsiveness. However, of the 29 apparent Aux/IAA proteins in Arabidopsis thaliana, fewer than half have roles established through mutant analysis. We identified iaa16-1, a dominant gain-of-function mutation in IAA16 (At3g04730), in a novel screen for reduced root responsiveness to abscisic acid. The iaa16-1 mutation also confers dramatically reduced auxin responses in a variety of assays, markedly restricts growth of adult plants, and abolishes fertility when homozygous. We compared iaa16-1 phenotypes with those of dominant mutants defective in the closely related IAA7/AXR2, IAA14/SLR, and IAA17/AXR3, along with the more distantly related IAA28, and found overlapping but distinct patterns of developmental defects. The identification and characterization of iaa16-1 provides a fuller understanding of the IAA7 / IAA14 / IAA16 / IAA17 clade of Aux/IAA proteins and the diverse roles of these repressors in hormone response and plant development.

Molecular basis for AUXIN RESPONSE FACTOR protein interaction and the control of auxin response repression

“…To understand the potential role of Aux/IAA protein multimerization in regulating auxin response, we combined an Aux/IAA protein gain-of-function mutation, which results in repressor hyperaccumulation and constitutive ARF repression (10), with PB1 domain mutations in planta. As previously described (25), overexpression of the iaa16-1 gain-offunction mutation in wild-type Arabidopsis resulted in stunted growth, decreased rosette diameter, infertility, and lack of apical dominance. However, overexpressing iaa16-1 K122A or iaa16-1 opca resulted in wild-type phenotypes (Fig.…”

Auxin signaling modules regulate maize inflorescence architecture

“…Stabilizing degron mutations in Arabidopsis Aux/IAA genes that are closely related to BIF1 (AXR2/IAA7, AXR3/IAA17, SLR/ IAA14, and IAA16) and BIF4 (IAA28) (Fig. S3) were reported to show decreased shoot branching, dwarfism, and partial infertility (33)(34)(35)(36)(37)(38). Some of these phenotypes may point to functional homology, as mutations in both species affect reproductive branching.…”

Tackling Plant Phosphate Starvation by the Roots

“…Furthermore, a vast number of PHR1-independent factors are described to be involved in Pi-starvation signaling (Ham et al, 2018;Azevedo and Saiardi, 2017;Puga et al, 2017) and might be involved in the crosstalk as well. As such, WRKY6 (Bakshi et al, 2015), WRKY75 (Devaiah et al, Auxin signaling TIR1 Auxin receptor PR, LR, RH, and imm PB Ganguly et al, 2010;Navarro et al, 2006;Ruegger et al, 1998 Auxin signaling IAA9 Repressor of ARF transcription factors LR PB Lewis et al, 2013 Auxin signaling IAA16 Repressor of ARF transcription factors PR, LR, and RH PB Rinaldi et al, 2012 Auxin signaling IAA17/AXR3 Repressor of ARF transcription factors PR, RH, and imm PB Navarro et al, 2006;Knox et al, 2003;Rouse et al, 1998;Leyser et al, 1996 Auxin (Sun et al, 2014) are described to be involved in the Pi-dependent lateral root formation, but further studies to elucidate their mode of actions are awaited. In summary, although the link between Pi starvation and lateral root formation is not always straightforward, Pi-starvation signaling has a clear link with auxin and might interact with lateral root development at multiple steps preceding lateral root formation ( Figure 1).…”