PIN-FORMED and PIN-LIKES auxin transport facilitators

Abstract

The phytohormone auxin influences virtually all aspects of plant growth and development. Auxin transport across membranes is facilitated by, among other proteins, members of the PIN-FORMED (PIN) and the structurally similar PIN-LIKES (PILS) families, which together govern directional cell-to-cell transport and intracellular accumulation of auxin. Canonical PIN proteins, which exhibit a polar localization in the plasma membrane, determine many patterning and directional growth responses. Conversely, the less-studied noncanonical PINs and PILS proteins, which mostly localize to the endoplasmic reticulum, attenuate cellular auxin responses. Here, and in the accompanying poster, we provide a brief summary of current knowledge of the structure, evolution, function and regulation of these auxin transport facilitators.

PIN-LIKES Coordinate Brassinosteroid Signaling with Nuclear Auxin Input in Arabidopsis thaliana

“…Besides local auxin metabolism, intercellular auxin transport is crucial to define auxin signaling gradients and maxima within plant tissues [14,15]. The canonical, plasma-membrane-localized PIN-FORMED (PIN) auxin efflux facilitators mainly determine the directionality of intercellular auxin transport and, hence, have outstanding developmental importance [16].…”

Role of the Cytokinin-Activated Type-B Response Regulators in Hormone Crosstalk

“…Genes related to auxin transport, including both efflux and influx carriers, are represented among the B-ARR targets and candidate targets ( Figure 2). The PIN auxin efflux carriers have a major role in the polar transport of auxin and establishing distribution of auxin in various cells and tissues to control growth and development [73][74][75]. The PILS auxin efflux carriers are also well represented and may be of particular interest, their role in the regulation of auxin activity not nearly as well understood as that of the PINs.…”

“…The PILS auxin efflux carriers are also well represented and may be of particular interest, their role in the regulation of auxin activity not nearly as well understood as that of the PINs. Unlike the PIN carriers, most of which are found at the plasma membrane and, therefore, regulate the cell to cell movement of auxin and its distribution with tissues, the PILS carriers are localized to the endoplasmic reticulum (ER) with a potential role of sequestering auxin within the ER lumen [73][74][75]. The AUX1/LAX gene family encodes auxin influx carriers.…”

Early Endosomal Trafficking Component BEN2/VPS45 Plays a Crucial Role in Internal Tissues in Regulating Root Growth and Meristem Size in Arabidopsis

“…On the other hand, PIN2 is expressed in outer tissues, including epidermis, cortex, and lateral root cap, and is typically localized to the apical side of the epidermal cells. PIN3, 4, and 7 are expressed in the vasculature and columellacells.MembersofPINproteinshaveauxineffluxactivityand expressedinpartiallyoverlappingpatterns (VannesteandFriml,2009;Sauer and Kleine-Vehn, 2019). Due to their partial redundancy, the single mutants display specific defects in shoot organ formation, gravitropic defects or moderate patterning defects, whereas the multiple mutants exhibit remarkable inhibition of root architecture (Friml et al, 2003;Blilou et al, 2005;Vieten et al, 2005).…”