Spatiotemporal auxin distribution in Arabidopsis tissues is regulated by anabolic and catabolic reactions under long-term ammonium stress

Kacper Dziewit,Ondřej Novák,Aleš Pěnčík,Bożena Szal,Katarzyna Dobrzyńska,Anna Podgórska

doi:10.1186/s12870-021-03385-9

Abstract

BackgroundThe plant hormone auxin is a major coordinator of plant growth and development in response to diverse environmental signals, including nutritional conditions. Sole ammonium (NH4+) nutrition is one of the unique growth-suppressing conditions for plants. Therefore, the quest to understand NH4+-mediated developmental defects led us to analyze auxin metabolism.ResultsIndole-3-acetic acid (IAA), the most predominant natural auxin, accumulates in the leaves and roots of mature Arabidopsis thaliana plants grown on NH4+, but not in the root tips. We found changes at the expressional level in reactions leading to IAA biosynthesis and deactivation in different tissues. Finally, NH4+ nutrition would facilitate the formation of inactive oxidized IAA as the final product.ConclusionsNH4+-mediated accelerated auxin turnover rates implicate transient and local IAA peaks. A noticeable auxin pattern in tissues correlates with the developmental adaptations of the short and highly branched root system of NH4+-grown plants. Therefore, the spatiotemporal distribution of auxin might be a root-shaping signal specific to adjust to NH4+-stress conditions.

Highlights

The plant hormone auxin is a major coordinator of plant growth and development in response to diverse environmental signals, including nutritional conditions
Ammonium cultivation caused reduced rosette development and a characteristic short and highly branched root phenotype Arabidopsis plants fed with NH4+ exhibited smaller rosettes and shorter roots, and smaller rosette diameter and primary root length values, compared to the plants fed with N O3− (Fig. 1A, B)
Staining of auxin reporters had a higher intensity in leaves and was heterogeneous in roots To examine the accumulation of auxins within tissues, Arabidopsis lines expressing DR5::GUS or DR5::Green fluorescent protein (GFP) reporter constructs were used [27]

Summary

Introduction

The plant hormone auxin is a major coordinator of plant growth and development in response to diverse environmental signals, including nutritional conditions. Sole ammonium (NH4+) nutrition is one of the unique growth-suppressing conditions for plants. When N H4+ is the sole source of nitrogen for plants, serious toxicity symptoms develop, leading to a condition known as the Dziewit et al BMC Plant Biology (2021) 21:602 research dedicated to understanding why growth arrest might be expected under NH4+ nutrition, the cause remains unclear. The plant hormone auxin is one of the fundamental regulators of plant growth and development. Indole3-acetic acid (IAA) is the major natural form of auxin in plant tissues, and it’s content is regulated by various developmental and environmental cues. An entire Trp independent pathway is possible, branching of its precursor anthranilate (ANT) [16]

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Discussion

Conclusion