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Plant roots acquire nutrients and water while managing interactions with the soil microbiota. The root endodermis provides an extracellular diffusion barrier through a network of lignified cell walls called Casparian strips, supported by subsequent formation of suberin lamellae. Whereas lignification is thought to be irreversible, suberin lamellae display plasticity, which is crucial for root adaptative responses. Although suberin is a major plant polymer, fundamental aspects of its biosynthesis and turnover have remained obscure. Plants shape their root system via lateral root formation, an auxin-induced process requiring local breaking and re-sealing of endodermal lignin and suberin barriers. Here, we show that differentiated endodermal cells have a specific, auxin-mediated transcriptional response dominated by cell wall remodelling genes. We identified two sets of auxin-regulated GDSL lipases. One is required for suberin synthesis, while the other can drive suberin degradation. These enzymes have key roles in suberization, driving root suberin plasticity.

Roots provide a means to plants for gathering belowground resources. They are plastic and can adapt to ever-changing environmental cues. The plasticity of the roots comes from their ability to branch out by developing lateral and/or adventitious roots. In this chapter, we make an attempt to document the diversity in plant root systems and understand their role in evolutionary adaptation. After a brief introduction to different root systems, such as homorhizic and allorhizic ones, the relationship of plant roots with their surroundings, i.e., the rhizosphere and its effect on adaptation, will be discussed. Despite the difficulty to conclusively construct a timeline of evolution of plant root systems, documented facts from previous publications are examined and an effort has been made to delve into how rooting structures in plants adapted to prevailing conditions by bringing about endogenous changes vis-à-vis evolutionary development and exogenous changes to their surroundings.