Directional root growth control is crucial for plant fitness. The degree of root growth deviation depends on several factors, whereby exogenous growth conditions have a profound impact. The perception of mechanical impedance by wild-type roots results in the modulation of root growth traits, and it is known that gravitropic stimulus influences distinct root movement patterns in concert with mechanoadaptation. Mutants with reduced shootward auxin transport are described as being numb towards mechanostimulus and gravistimulus, whereby different growth conditions on agar-supplemented medium have a profound effect on how much directional root growth and root movement patterns differ between wild types and mutants. To reduce the impact of unilateral mechanostimulus on roots grown along agar-supplemented medium, we compared the root movement of Col-0 and auxin resistant 1-7 in a root penetration assay to test how both lines adjust the growth patterns of evenly mechanostimulated roots. We combined the assay with the D-root system to reduce light-induced growth deviation. Moreover, the impact of sucrose supplementation in the growth medium was investigated because exogenous sugar enhances root growth deviation in the vertical direction. Overall, we observed a more regular growth pattern for Col-0 but evaluated a higher level of skewing of aux1-7 compared to the wild type than known from published data. Finally, the tracking of the growth rate of the gravistimulated roots revealed that Col-0 has a throttling elongation rate during the bending process, but aux1-7 does not.

• Keywords
• AUX1, AUXIN-RESISTANT 1, D-root system, directional root growth, gravitropic response, mechanoadaptation, mechanostimulus, root elongation rate, root penetration assay, root skewing,
• Publication type
• Journal Article MeSH

The plant nucleus plays an irreplaceable role in cellular control and regulation by auxin (indole-3-acetic acid, IAA) mainly because canonical auxin signaling takes place here. Auxin can enter the nucleus from either the endoplasmic reticulum or cytosol. Therefore, new information about the auxin metabolome (auxinome) in the nucleus can illuminate our understanding of subcellular auxin homeostasis. Different methods of nuclear isolation from various plant tissues have been described previously, but information about auxin metabolite levels in nuclei is still fragmented and insufficient. Herein, we tested several published nucleus isolation protocols based on differential centrifugation or flow cytometry. The optimized sorting protocol leading to promising yield, intactness, and purity was then combined with an ultra-sensitive mass spectrometry analysis. Using this approach, we can present the first complex report on the auxinome of isolated nuclei from cell cultures of Arabidopsis and tobacco. Moreover, our results show dynamic changes in auxin homeostasis at the intranuclear level after treatment of protoplasts with free IAA, or indole as a precursor of auxin biosynthesis. Finally, we can conclude that the methodological procedure combining flow cytometry and mass spectrometry offers new horizons for the study of auxin homeostasis at the subcellular level.

• Keywords
• auxin, auxin metabolism, flow cytometry, nucleus, subcellular fractionation,
• MeSH
• Arabidopsis drug effects   metabolism   ultrastructure   MeSH
• Cell Nucleus drug effects   metabolism   ultrastructure   MeSH
• Cell Culture Techniques MeSH
• Centrifugation methods   MeSH
• Cell Fractionation instrumentation   methods   MeSH
• Mass Spectrometry MeSH
• Homeostasis physiology   MeSH
• Indoles metabolism   pharmacology   MeSH
• Indoleacetic Acids metabolism   MeSH
• Protoplasts chemistry   MeSH
• Flow Cytometry MeSH
• Plant Growth Regulators metabolism   MeSH
• Plant Cells drug effects   metabolism   ultrastructure   MeSH
• Nicotiana drug effects   metabolism   ultrastructure   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• indole MeSH Browser
• Indoles MeSH
• Indoleacetic Acids MeSH
• Plant Growth Regulators MeSH

• Keywords
• AUX/IAA transcriptional regulators, Arabidopsis, Auxin F-Box (AFB), Auxin Response Factors (ARFs), Transport Inhibitor Response 1 (TIR1), auxin, canonical auxin signalling pathway, indole-3-acetic acid (IAA), kinase, receptor, TIR1/AFB co-receptor, non-canonical auxin signalling pathway, ubiquitination,
• MeSH
• Plant Physiological Phenomena * MeSH
• Indoleacetic Acids metabolism   MeSH
• Signal Transduction physiology   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Indoleacetic Acids MeSH