How plants get round problems: new insights into the root obstacle avoidance response

This article is a Commentary on Jacobsen et al. (2021), 231: 225–242. ‘The response to mechanical impedance complex interaction of differently timed responses.’ Currently, it believed that the root tip encountering physical barrier combination negative thigmotropism (a touch) and positive gravitropism (Massa & Gilroy, 2003). Interestingly, both responses are mediated by redistribution plant hormone auxin via PIN efflux carriers (Lee al., 2020). In addition auxin, several other signals, such as reactive oxygen species (ROS), calcium ion (Ca2+) pH, have been shown be involved in regulation (Nakagawa 2007). Moreover, causes decrease cell elongation, which caused calcium, ethylene signalling (Okamoto 2021). To analyse Arabidopsis an vitro artificial system, investigated changes transcriptome signalling. It was found ROS biosynthesis-related terms were overrepresented among genes regulated after stimulation. biosynthesis dynamically during response. The authors also key genes, ETHYLENE INSENSTIVE LIKE 2 (EIL2) RESPONSE FACTOR (ERF) ERF1A ERF4, upregulated early phases these ethylene-related dynamic (IAA30, IAA14) conjugation (GH3s, BRU6, DFL1/2) differentially expressed onset obstacle avoidance Together, data give new insights into role ROS, ethylene, pathways provided platform for proceed dissect spatiotemporal dimensions process. Stimuli perceived columella can affect expansion elongation/differentiation zone (EDZ) change direction growth. During graviresponse, cells sense inclination organ within gravitational field thanks sedimentation dense starch-filled amyloplasts act statoliths (Su 2017). triggers shift lateral transport towards lower side, PIN-transporters, resulting differential elongation causing bend. Thigmotropism cells, still unknown mechanism, stimulus asymmetrical EDZ (Zhang Friml, spatial characterization signalling, performed confocal analysis hydrogen peroxide (H2O2) reporter HyPer. line showed upregulation cap avoidance. using CellROX Deep Red staining reveal levels, content EDZ. length not inhibited resistant mutant etr1-1 ethylene-insensitive mutants (ein2, aux1, eir1), accordance with literature 2008, increase hair growth presence chemical inhibitors (aminoethoxyvinylglycine, AVG) (silver thiosulphate, STS). These all reinforce Recent work has Through marker lines mDII-ndTomato/DII-m3xVenus, overall concentration. A similar trend detected DR5rev::3xVENUS-N7 line, but difference only significant stele, could due tissue-specific variation confirmed asymmetry distribution across root. responses. initial bend thigmotropism, whereas second downward gravitropism. Notably, done revealed bending takes place 20 min 2020), indicating rapid detailed angle variations, great insight specific hormones through Transcriptomic suggest transient addition, loss-of-function indicates necessary from very avoidance, showing phenotype already at 10 encounter. Similarly, atrbohD/F double mutant, impaired pathway, hindered response, albeit mutant. Previously, PIN-mediated roles two However, time course neither AUX1 nor PIN2 transporters, essential gravitropic Taken together, corroborate model stimuli trigger accumulation auxin. signals then propagate redistribution. At EDZ, regulate expansion. appears plays pivotal earlier stages transporters might important thigmotropic despite being Despite attempts link pathways, details ROS–ethylene–auxin crosstalk remain discovered. recent paper follows cytoplasmic Ca2+ Since production requires (Monshausen 2009) highly connected (Vanneste 2013), between Understanding agronomic relevance, since soil drying compaction reduce crop yields (Whalley 2008). One potentially relevant seldomly considered relation penetration, anchorage tip, advance soil. Genotypes hairs advantage penetration high-strength layers relative hairless genotypes (Haling 2013). Root anchor increasing friction induce (Bengough 2011). Jacobson show longer, denser, emerge closer encountered. effects completely lost shows normal formation. morphogenesis hormonal (Shibata 2019). shedding light mediating induction upon impedance, ROOT HAIR DEFECTIVE (RHD2), enzyme required linked (Foreman 2003), hinting possible cross talk Climate increases odds worsening drought, results water stress how compact modulate direct manner limiting diffusion away (Pandey intricate mechanisms regulating guide breeding crops more resilient harsh conditions prospects food security. wish thank Leverhulme Trust (RPG-2018-137) Biotechnology Biological Sciences Research Council (BBSRC) (BB/N010124/1) their support projects Kepinski laboratory.