Local auxin biosynthesis modulates gradient-directed planar polarity in Arabidopsis

Abstract

The coordination of cell polarity within the plane of a single tissue layer (planar polarity) is a crucial task during development of multicellular organisms. Mechanisms underlying establishment of planar polarity, however, differ substantially between plants and animals. In Arabidopsis thaliana, planar polarity of root-hair positioning along epidermal cells is coordinated towards maximum concentration of an auxin gradient in the root tip. This gradient has been hypothesized to be sink-driven and computational modelling suggests that auxin efflux carrier activity may be sufficient to generate the gradient in the absence of auxin biosynthesis in the root. Here, we demonstrate that the Raf-like kinase CONSTITUTIVE TRIPLE RESPONSE1 (CTR1; Refs 8, 9) acts as a concentration-dependent repressor of a biosynthesis-dependent auxin gradient that modulates planar polarity in the root tip. We analysed auxin biosynthesis and concentration gradients in a variety of root-hair-position mutants affected in CTR1 activity, auxin biosynthesis and transport. Our results reveal that planar polarity relies on influx- and efflux-carrier-mediated auxin redistribution from a local biosynthesis maximum. Thus, a local source of auxin biosynthesis contributes to gradient homeostasis during long-range coordination of cellular morphogenesis.

ER-localized auxin transporter PIN8 regulates auxin homeostasis and male gametophyte development in Arabidopsis

“…A crucial aspect of auxin action is its graded distribution (auxin gradients) that depends on local auxin biosynthesis [14][15][16] and directional, intercellular auxin transport 7,17,18 . The polar auxin transport has an essential role in most auxin-regulated processes and is mediated by auxin influx proteins from the AUX1/LAX family 19 , by PIN auxin efflux proteins 20 and by homologues of the ABCB multiple drug resistance transporters 21,22 .…”

A novel putative auxin carrier family regulates intracellular auxin homeostasis in plants

“…PILS activity affects the level of endogenous auxin indole-3-acetic acid (IAA), presumably via intracellular accumulation and metabolism. Our findings reveal that the transport machinery to compartmentalize auxin within the cell is of an unexpected molecular complexity and demonstrate this compartmentalization to be functionally important for a number of developmental processes.Prominent auxin carriers with fundamental importance during plant development are PIN-FORMED (PIN) proteins [1][2][3]6,9,15 . PIN1-type auxin carriers regulate the directional intercellular auxin transport at the plasma membrane.…”

“…The distribution of auxin depends on both auxin metabolism (biosynthesis, conjugation and degradation) [8][9][10] and cellular auxin transport [11][12][13][14][15] . We identified in silico a novel putative auxin transport facilitator family, called PIN-LIKES (PILS).…”

“…Prominent auxin carriers with fundamental importance during plant development are PIN-FORMED (PIN) proteins [1][2][3]6,9,15 . PIN1-type auxin carriers regulate the directional intercellular auxin transport at the plasma membrane.…”

Understanding the role of Oryza sativa OsPILS (PIN Like) genes in auxin signaling

“…PIN genes shows distinct pattern of cellular and sub-cellular localization in root and shoot and shows tissue specific expression Blilou et al 2005;Paponov et al 2005). AtPIN1 localizes polarly in plasma membrane, and upon pharmacological disruption, it immediately relocalizes, suggesting conceptual basis of auxin flux affects tropic response and patterning (Estelle 1998;Friml and Palme 2002;Ikeda et al 2009;Forestan and Varotto 2012). It has reported that rice OsPIN1 gene expressed in root cap, OsPIN1b, OsPIN1c and OsPIN9 predominantly expressed in stele and OsPIN1b, OsPIN1c, OsPIN5a and OsPIN5b found to be expressed in meristem tissues (Wang et al 2009b).…”