The heterozygous abp1/ABP1 insertional mutant has defects in functions requiring polar auxin transport and in regulation of early auxin-regulated genes

Abstract

P>AUXIN-BINDING PROTEIN 1 (ABP1) is not easily accessible for molecular studies because the homozygous T-DNA insertion mutant is embryo-lethal. We found that the heterozygous abp1/ABP1 insertion mutant has defects in auxin physiology-related responses: higher root slanting angles, longer hypocotyls, agravitropic roots and hypocotyls, aphototropic hypocotyls, and decreased apical dominance. Heterozygous plants flowered earlier than wild-type plants under short-day conditions. The length of the main root, the lateral root density and the hypocotyl length were little altered in the mutant in response to auxin. Compared to wild-type plants, transcription of early auxin-regulated genes (IAA2, IAA11, IAA13, IAA14, IAA19, IAA20, SAUR9, SAUR15, SAUR23, GH3.5 and ABP1) was less strongly up-regulated in the mutant by 0.1, 1 and 10 mu m IAA. Surprisingly, ABP1 was itself an early auxin-up-regulated gene. IAA uptake into the mutant seedlings during auxin treatments was indistinguishable from wild-type. Basipetal auxin transport in young roots was slower in the mutant, indicating a PIN2/EIR1 defect, while acropetal transport was indistinguishable from wild-type. In the eir1 background, three of the early auxin-regulated genes tested (IAA2, IAA13 and ABP1) were more strongly induced by 1 mu m IAA in comparison to wild-type, but eight of them were less up-regulated in comparison to wild-type. Similar but not identical disturbances in regulation of early auxin-regulated genes indicate tight functional linkage of ABP1 and auxin transport regulation. We hypothesize that ABP1 is involved in the regulation of polar auxin transport, and thus affects local auxin concentration and early auxin gene regulation. In turn, ABP1 itself is under the transcriptional control of auxin.

Keywords

abp1; ABP1 mutant; AUXIN-BINDING PROTEIN 1; auxin-induced transcription; gravitropism; phototropism; auxin transport

Published in

Plant Journal
2011, volume: 65, number: 2, pages: 282-294

SLU Authors

• Fischer, Urs

  • Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Developmental Biology
Botany

Publication identifier

• DOI: https://doi.org/10.1111/j.1365-313X.2010.04420.x

Permanent link to this page (URI)

https://res.slu.se/id/publ/83604