Recent insights into metabolic and signalling events of directional root growth regulation and its implications for sustainable crop production systems

Abstract

Roots are sensors evolved to simultaneously respond to manifold signals, which allow the plant to survive. Root growth responses, including the modulation of directional root growth, were shown to be differently regulated when the root is exposed to a combination of exogenous stimuli compared to an individual stress trigger. Several studies pointed especially to the impact of the negative phototropic response of roots, which interferes with the adaptation of directional root growth upon additional gravitropic, halotropic or mechanical triggers. This review will provide a general overview of known cellular, molecular and signalling mechanisms involved in directional root growth regulation upon exogenous stimuli. Furthermore, we summarise recent experimental approaches to dissect which root growth responses are regulated upon which individual trigger. Finally, we provide a general overview of how to implement the knowledge gained to improve plant breeding.

Dynamic Dark Root Chamber: Advancing non-invasive phenotyping of roots kept in darkness using infrared imaging

“…Different wavelengths of light spectrum can provide energy for photosynthesis, or act as a signal that informs plants about the quality of the light source (Miotto et al ., 2021; van Gelderen et al ., 2021). Plants express various photoreceptors that sense different wavelengths of light and accordingly trigger specific responses in the shoot, but also in the root (Van Gelderen, Kang and Pierik, 2018; Retzer and Weckwerth, 2021, 2023; Lopez et al ., 2023). While shoots are directly exposed to light, roots are usually shielded from direct illumination by the soil.…”

“…The root is a crucial organ that anchors the plant in the soil and facilitates water and nutrient uptake which is essential for plant growth and survival (Pierik and Testerink, 2014; Retzer and Weckwerth, 2021, 2023; Pree et al ., 2023). While it is relatively easy to measure and analyze the shoot phenotype of plants in the field or in the laboratory under physiological relevant conditions, it is still very difficult, time-consuming, or harmful for the root to obtain dynamic data of the whole root system (York, Griffiths and Maaz, 2022).…”

“…Roots have evolved to grow vertically downward in the soil by sensing and responding to gravity and light signals (Wyatt and Kiss, 2013; Retzer and Weckwerth, 2023). However, recent studies have revealed that exposing roots to light not only influences their direction of growth, but also interferes with other root responses, altering their growth rate and function compared to roots grown in the dark (Xu et al ., 2013; Silva-Navas et al ., 2015; Shi et al ., 2018; García-González, Lacek and Retzer, 2021).…”

Deciphering the biological processes in root hairs required for N-self-fertilizing cereals

“…Plants evolved a fine-tuned network of intracellular processes to adapt to environmental changes leading to fast adaptation responses. Among other root growth responses, root hair outgrowth and exudate release belong to the so-called fast responses (Retzer and Weckwerth, 2021;Retzer and Weckwerth, 2023). Root hairs are extensions of the epidermal cells of roots that increase the surface area of the root and facilitate nutrient and water uptake from the soil (Grierson et al, 2014;Wu et al, 2019;Retzer and Weckwerth, 2021).…”

“…The increasing population and the loss of fertile soil requires holistic approaches to enhance sustainable agriculture (Retzer and Weckwerth, 2023). Studies have shown that cereal crops deficient in root hair outgrowth exhibit reduced fitness (Giehl and von Wireń, 2014;Lopez et al, 2023;Xu et al, 2023).…”