Auxin binding protein 1 (ABP1) is not required for either auxin signaling or Arabidopsis development

Abstract

Auxin binding protein 1 (ABP1) has been studied for decades. It has been suggested that ABP1 functions as an auxin receptor and has an essential role in many developmental processes. Here we present our unexpected findings that ABP1 is neither required for auxin signaling nor necessary for plant development under normal growth conditions. We used our ribozyme-based CRISPR technology to generate an Arabidopsis abp1 mutant that contains a 5-bp deletion in the first exon of ABP1, which resulted in a frameshift and introduction of early stop codons. We also identified a T-DNA insertion abp1 allele that harbors a T-DNA insertion located 27 bp downstream of the ATG start codon in the first exon. We show that the two new abp1 mutants are null alleles. Surprisingly, our new abp1 mutant plants do not display any obvious developmental defects. In fact, the mutant plants are indistinguishable from wild-type plants at every developmental stage analyzed. Furthermore, the abp1 plants are not resistant to exogenous auxin. At the molecular level, we find that the induction of known auxin-regulated genes is similar in both wild-type and abp1 plants in response to auxin treatments. We conclude that ABP1 is not a key component in auxin signaling or Arabidopsis development.

Reassessing the Roles of PIN Proteins and Anticlinal Microtubules during Pavement Cell Morphogenesis

“…S3). The results we present here are consistent with the negative results on ABP1 (Gao et al, 2015) and indicate that auxin efflux carriers do not control lobe initiation.…”

“…The negative data with ric4, and the lack of stable patterns of microtubules along the anticlinal wall, also suggest that there are no stable cortical actin domains that are proposed to alternate with microtubules via a PIN-based mechanism (Fu et al, 2005;Nagawa et al, 2012). We are not claiming that auxin has no role in lobe formation, as long-term treatments with exogenous auxin can increase cell lobe number (Xu et al, 2010;Gao et al, 2015). Exogenous auxin may extend the developmental window during which pavement cells are competent to form lobes, or auxin may have a general effect on the cell wall that makes lobing more permissive.…”

“…This model has been challenged by a recently generated null allele of ABP1 that had no pavement cell phenotype (Gao et al, 2015). In this article, we describe a broader genetic analysis of the proposed auxin signaling network and demonstrate that there is no clear evidence for PIN-based control of lobe initiation.…”

Master and servant: Regulation of auxin transporters by FKBPs and cyclophilins

“…However, an effect for TWD1 on actin filament organization and dynamics has not yet been shown. In contrast, a recent report questioned the role of ABP1 in auxin signaling, auxin-mediated actin organization and plant development [121] although this study does obviously not affect previous biochemical proof of NPA binding to ABP1 [122].…”

PaCeQuant: A Tool for High-Throughput Quantification of Pavement Cell Shape Characteristics

“…These methods oversimplify PC shape and contain no informational value on the number and degree of lobes (Ivakov and Persson, 2013;Wu et al, 2016). To quantify lobe numbers, two main approaches are widely used: skeletonbased detection and manual quantification, which typically underestimate the number of lobes or calculate the number of lobes per area rather than per cell, respectively (Xu et al, 2010;Gao et al, 2015). More recently, a MATLAB-based tool was developed, which aims to provide a platform for objective and robust quantification of lobe number and shape characteristics by analysis of a refined convex hull (Wu et al, 2016).…”