Interaction of PIN and PGP transport mechanisms in auxin distribution-dependent development

Abstract

The signalling molecule auxin controls plant morphogenesis via its activity gradients, which are produced by intercellular auxin transport. Cellular auxin efflux is the rate-limiting step in this process and depends on PIN and phosphoglycoprotein (PGP) auxin transporters. Mutual roles for these proteins in auxin transport are unclear, as is the significance of their interactions for plant development. Here, we have analysed the importance of the functional interaction between PIN-and PGP-dependent auxin transport in development. We show by analysis of inducible overexpression lines that PINs and PGPs define distinct auxin transport mechanisms: both mediate auxin efflux but they play diverse developmental roles. Components of both systems are expressed during embryogenesis, organogenesis and tropisms, and they interact genetically in both synergistic and antagonistic fashions. A concerted action of PIN-and PGP-dependent efflux systems is required for asymmetric auxin distribution during these processes. We propose a model in which PGP-mediated efflux controls auxin levels in auxin channel-forming cells and, thus, auxin availability for PIN-dependent vectorial auxin movement.

Block of ATP-Binding Cassette B19 Ion Channel Activity by 5-Nitro-2-(3-Phenylpropylamino)-Benzoic Acid Impairs Polar Auxin Transport and Root Gravitropism

“…The ABCB19 protein is present predominantly in the central cylinder and cortex of the root, consistent with its role in rootward auxin transport Mravec et al, 2008), whereas the closely related ABCB4 is restricted to the lateral root cap and epidermis (Cho et al, 2007), where it functions in shootward auxin transport . Loss of ABCB4 function alters the timing and spatial pattern of gravitropic curvature development, apparently because the gravityinduced auxin gradient across the root is less rapidly dissipated by normal shootward (basipetal) transport of the hormone through the elongation zone .…”

Master and servant: Regulation of auxin transporters by FKBPs and cyclophilins

“…The energization of PINs is less clear and hypothesized based on the fact that PINs do not possess ATP-binding domains [128]. Interestingly, complex functional interactions among some PINs and ABCBs have been reported [19][20][21], however, the biological relevance and mechanism of these interactions are far from being understood.…”

“…Mutations in PIN1 and combined mutations in other PIN genes with PIN1 result in organogenesis defects, indicating that PINs mediate directional auxin flow that regulates organogenesis [17,18]. In contrast, abcb1, 19 mutants although significantly dwarfed display only subtle morphological defects [19,20] suggesting that ABCBs function primarily in export of auxin out of meristematic tissues with high auxin concentrations, and in maintenance of long-distance auxin flows required for physiological processes (reviewed in Refs. [4,21]).…”

“…It is worth mentioning though that ion channel function has been described for some mammalian ABC transporters [46]. It has also been reported that co-expression of ABCB and PIN combinations leads to synergistic transport rates and alters substrate specificities and inhibitor sensitivities [20,21]. The individual roles of ABCBs and PINs in these interactions, e.g., which protein functions as a transporter and which as a regulator, are far from being understood.…”

Manipulation of Auxin Transport in Plant Roots during Rhizobium Symbiosis and Nematode Parasitism

“…Genetic approaches in Arabidopsis have identified two groups of proteins that are involved in auxin export from cells: PIN-FORMED (PIN) and MULTIDRUG RESISTANCE/ P-GLYCOPROTEIN (MDR/PGP) proteins. Each of these families of plasma membrane-localized proteins represents a distinct auxin transport mechanism and have been shown to perform cellular auxin efflux in both plant and heterologous systems (Petrá sek et al, 2006;Mravec et al, 2008). The PIN family can be subdivided into full-length and short endomembrane proteins (Mravec et al, 2009).…”