PIN‐mediated polar auxin transport regulations in plant tropic responses

Abstract

Tropisms, growth responses to environmental stimuli such as light or gravity, are spectacular examples of adaptive plant development. The plant hormone auxin serves as a major coordinative signal. The PIN auxin exporters, through their dynamic polar subcellular localizations, redirect auxin fluxes in response to environmental stimuli and the resulting auxin gradients across organs underly differential cell elongation and bending. In this review, we discuss recent advances concerning regulations of PIN polarity during tropisms, focusing on PIN phosphorylation and trafficking. We also cover how environmental cues regulate PIN actions during tropisms, and a crucial role of auxin feedback on PIN polarity during bending termination. Finally, the interactions between different tropisms are reviewed to understand plant adaptive growth in the natural environment.

Biosynthesis and Roles of Salicylic Acid in Balancing Stress Response and Growth in Plants

“…These effects of SA on root growth and development involve PIN auxin transporters. A dynamic control of cellular PIN polarity affects the directionality of auxin fluxes and modulates auxin-regulated growth and developmental processes [55][56][57]. The polar distribution of PIN proteins is primarily established by clathrin-mediated endocytosis and their recycling to the plasma membrane as the initial secretion of newly synthesized PIN proteins is not polar [58] (Figure 3).…”

Role of Basal ABA in Plant Growth and Development

“…However, the mode of ABA-mediated growth regulation varies depending on concentrations, timing, and tissues, showing both positive and negative effects on growth [ 5 ]. Context-dependent positive and negative growth regulation is known for other hormones, such as ethylene, CK and auxin [ 56 , 57 , 58 ]. This coincides with the prominent role of hormone crosstalk in ABA-mediated growth.…”

A Retro-Perspective on Auxin Transport

“…For a long time, the auxin community mainly focused on the establishment and maintenance of transporter polarity, with a special emphasis on the trafficking routes of PIN proteins (Rakusova et al, 2015;Zhou and Luo, 2018;Han et al, 2021). In short, PINs are constitutively internalized on clathrin-coated vesicles and recycled back to the plasma membrane.…”

“…In short, PINs are constitutively internalized on clathrin-coated vesicles and recycled back to the plasma membrane. These processes are regulated by a wealth of regulatory factors, including various GTPases, ARF-GEFs, and ARF-GAPs (Chen and Friml, 2014;Adamowski and Friml, 2015;Friml, 2021;Han et al, 2021). Another regulatory module orchestrating PIN polarity is formed by the interplay of AGC kinases and protein phosphatase 2A which regulate the phosphorylation status of cytoplasmic PIN loops (for details, see below; Michniewicz et al, 2007;Robert and Offringa, 2008;Huang et al, 2010;Offringa and Huang, 2013).…”