Local, Efflux-Dependent Auxin Gradients as a Common Module for Plant Organ Formation

Abstract

Plants, compared to animals, exhibit an amazing adaptability and plasticity in their development. This is largely dependent on the ability of plants to form new organs, such as lateral roots, leaves, and flowers during postembryonic development. Organ primordia develop from founder cell populations into organs by coordinated cell division and differentiation. Here, we show that organ formation in Arabidopsis involves dynamic gradients of the signaling molecule auxin with maxima at the primordia tips. These gradients are mediated by cellular efflux requiring asymmetrically localized PIN proteins, which represent a functionally redundant network for auxin distribution in both aerial and underground organs. PIN1 polar localization undergoes a dynamic rearrangement, which correlates with establishment of auxin gradients and primordium development. Our results suggest that PIN-dependent, local auxin gradients represent a common module for formation of all plant organs, regardless of their mature morphology or developmental origin.

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

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The phytohormone auxin acts as a prominent signal, providing, by its local accumulation or depletion in selected cells, a spatial and temporal reference for changes in the developmental program [1][2][3][4][5][6][7] . 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] .

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“…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.…”

“…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.…”

LEAFY HEAD2, which encodes a putative RNA-binding protein, regulates shoot development of rice

“…The field inhibitory hypothesis is applauded to explain plant phyllotaxy, proposing that the new primordia will form only after escaping the biochemical constraint made by the existing Involvement of LHD2 in shoot development 268 npg primordia [7]. Recent works revealed that the biochemical constraints could be established by polar auxin transport [8][9][10]. The initiation of lateral organ primordia is induced by a local auxin maximum accumulated in the peripheral zone of SAM, then next primodium formation may initiate at the site most distant to the preexisting primordium because the established primordia act as a sink to deplete auxin accumulation within surrounding cells [7][8][9][10].…”

“…Recent works revealed that the biochemical constraints could be established by polar auxin transport [8][9][10]. The initiation of lateral organ primordia is induced by a local auxin maximum accumulated in the peripheral zone of SAM, then next primodium formation may initiate at the site most distant to the preexisting primordium because the established primordia act as a sink to deplete auxin accumulation within surrounding cells [7][8][9][10]. Since changes in size and/or organization of SAM can alter the field in which auxin acts, a number of mutants exhibit close association of abnormal phyllotaxy with modified meristems [11][12][13][14].…”