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AUX/LAX family of auxin influx carriers-an overview.

Swarup R, Péret B - Front Plant Sci (2012)

Bottom Line: Auxin is unique among plant hormones for exhibiting polar transport.Of the four AUX/LAX genes, AUX1 regulates root gravitropism, root hair development and leaf phyllotaxy whereas LAX2 regulates vascular development in cotyledons.Both AUX1 and LAX3 have been implicated in lateral root (LR) development as well as apical hook formation whereas both AUX1 and LAX1 and possibly LAX2 are required for leaf phyllotactic patterning.

View Article: PubMed Central - PubMed

Affiliation: School of Biosciences and Centre for Plant Integrative Biology, University of Nottingham Loughborough, UK.

ABSTRACT
Auxin regulates several aspects of plant growth and development. Auxin is unique among plant hormones for exhibiting polar transport. Indole-3-acetic acid (IAA), the major form of auxin in higher plants, is a weak acid and its intercellular movement is facilitated by auxin influx and efflux carriers. Polarity of auxin movement is provided by asymmetric localization of auxin carriers (mainly PIN efflux carriers). PIN-FORMED (PIN) and P-GLYCOPROTEIN (PGP) family of proteins are major auxin efflux carriers whereas AUXIN1/LIKE-AUX1 (AUX/LAX) are major auxin influx carriers. Genetic and biochemical evidence show that each member of the AUX/LAX family is a functional auxin influx carrier and mediate auxin related developmental programmes in different organs and tissues. Of the four AUX/LAX genes, AUX1 regulates root gravitropism, root hair development and leaf phyllotaxy whereas LAX2 regulates vascular development in cotyledons. Both AUX1 and LAX3 have been implicated in lateral root (LR) development as well as apical hook formation whereas both AUX1 and LAX1 and possibly LAX2 are required for leaf phyllotactic patterning.

No MeSH data available.


Related in: MedlinePlus

Mutations in AUX/LAX genes result in auxin related developmental defects. AUX1 regulates root gravitropism (Swarup et al., 2001, 2004, 2005). AUX1 is expressed in tissues that are involved in gravity perception, signal transmission, and response and mutation in aux1 cause agravitropic roots (A). Both AUX1 and LAX3 regulate lateral root development (Swarup et al., 2008). AUX1 is expressed in lateral root primordia whereas LAX3 in the cortical and epidermal cells in contact with the primordia and aux1 lax3 double mutants have severely delayed lateral root emergence (B). LAX2 regulates vascular patterning in cotyloedons (Péret et al., 2012). LAX2 is expressed in the vascular tissues during embryo development and lax2 mutants show vascular breaks in the cotyledons (C). (Scale bars 20 μm).
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Figure 3: Mutations in AUX/LAX genes result in auxin related developmental defects. AUX1 regulates root gravitropism (Swarup et al., 2001, 2004, 2005). AUX1 is expressed in tissues that are involved in gravity perception, signal transmission, and response and mutation in aux1 cause agravitropic roots (A). Both AUX1 and LAX3 regulate lateral root development (Swarup et al., 2008). AUX1 is expressed in lateral root primordia whereas LAX3 in the cortical and epidermal cells in contact with the primordia and aux1 lax3 double mutants have severely delayed lateral root emergence (B). LAX2 regulates vascular patterning in cotyloedons (Péret et al., 2012). LAX2 is expressed in the vascular tissues during embryo development and lax2 mutants show vascular breaks in the cotyledons (C). (Scale bars 20 μm).

Mentions: In Arabidopsis, AUX1 belongs to a small gene family comprising of four highly conserved genes, AUX1 and LIKE-AUX1 (LAX) genes, LAX1, LAX2, and LAX3 and form a plant- specific subclass within the amino acid/auxin permease (AAAP) super family (Young et al., 1999; Péret et al., 2012) (Figure 2). These genes encode multi membrane spanning transmembrane proteins. In a very elegant study, Swarup et al. (2004) using a pH sensitive YFP as a probe to determine the topology of AUX1 showed that AUX1 has 11 transmembrane segments with N terminal residing inside the cell and C-terminal outside. AUX/LAX genes share extensive sequence similarity (Péret et al., 2012). There is ample evidence to suggest that these genes have originated from a common ancestor through gene duplication. For example, AUX1 shares 82, 78, and 76% identity with LAX1, LAX2, and LAX3, respectively, and they also show well conserved gene structure (Péret et al., 2012) (Figure 2), At functional level evidence has been provided that these genes encode functional auxin influx carriers (Yang et al., 2006; Swarup et al., 2008; Péret et al., 2012) and mutations in these genes result in auxin related developmental defects (Figure 3; Bennett et al., 1996; Swarup et al., 2001, 2004, 2005, 2007, 2008; Bainbridge et al., 2008; Péret et al., 2012). Despite the conservation of biochemical function, these genes show mostly non-redundant expression and during the course of evolution have subfunctionalized to facilitate auxin related developmental programmes in different plant organs and tissues as reviewed below.


AUX/LAX family of auxin influx carriers-an overview.

Swarup R, Péret B - Front Plant Sci (2012)

Mutations in AUX/LAX genes result in auxin related developmental defects. AUX1 regulates root gravitropism (Swarup et al., 2001, 2004, 2005). AUX1 is expressed in tissues that are involved in gravity perception, signal transmission, and response and mutation in aux1 cause agravitropic roots (A). Both AUX1 and LAX3 regulate lateral root development (Swarup et al., 2008). AUX1 is expressed in lateral root primordia whereas LAX3 in the cortical and epidermal cells in contact with the primordia and aux1 lax3 double mutants have severely delayed lateral root emergence (B). LAX2 regulates vascular patterning in cotyloedons (Péret et al., 2012). LAX2 is expressed in the vascular tissues during embryo development and lax2 mutants show vascular breaks in the cotyledons (C). (Scale bars 20 μm).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3475149&req=5

Figure 3: Mutations in AUX/LAX genes result in auxin related developmental defects. AUX1 regulates root gravitropism (Swarup et al., 2001, 2004, 2005). AUX1 is expressed in tissues that are involved in gravity perception, signal transmission, and response and mutation in aux1 cause agravitropic roots (A). Both AUX1 and LAX3 regulate lateral root development (Swarup et al., 2008). AUX1 is expressed in lateral root primordia whereas LAX3 in the cortical and epidermal cells in contact with the primordia and aux1 lax3 double mutants have severely delayed lateral root emergence (B). LAX2 regulates vascular patterning in cotyloedons (Péret et al., 2012). LAX2 is expressed in the vascular tissues during embryo development and lax2 mutants show vascular breaks in the cotyledons (C). (Scale bars 20 μm).
Mentions: In Arabidopsis, AUX1 belongs to a small gene family comprising of four highly conserved genes, AUX1 and LIKE-AUX1 (LAX) genes, LAX1, LAX2, and LAX3 and form a plant- specific subclass within the amino acid/auxin permease (AAAP) super family (Young et al., 1999; Péret et al., 2012) (Figure 2). These genes encode multi membrane spanning transmembrane proteins. In a very elegant study, Swarup et al. (2004) using a pH sensitive YFP as a probe to determine the topology of AUX1 showed that AUX1 has 11 transmembrane segments with N terminal residing inside the cell and C-terminal outside. AUX/LAX genes share extensive sequence similarity (Péret et al., 2012). There is ample evidence to suggest that these genes have originated from a common ancestor through gene duplication. For example, AUX1 shares 82, 78, and 76% identity with LAX1, LAX2, and LAX3, respectively, and they also show well conserved gene structure (Péret et al., 2012) (Figure 2), At functional level evidence has been provided that these genes encode functional auxin influx carriers (Yang et al., 2006; Swarup et al., 2008; Péret et al., 2012) and mutations in these genes result in auxin related developmental defects (Figure 3; Bennett et al., 1996; Swarup et al., 2001, 2004, 2005, 2007, 2008; Bainbridge et al., 2008; Péret et al., 2012). Despite the conservation of biochemical function, these genes show mostly non-redundant expression and during the course of evolution have subfunctionalized to facilitate auxin related developmental programmes in different plant organs and tissues as reviewed below.

Bottom Line: Auxin is unique among plant hormones for exhibiting polar transport.Of the four AUX/LAX genes, AUX1 regulates root gravitropism, root hair development and leaf phyllotaxy whereas LAX2 regulates vascular development in cotyledons.Both AUX1 and LAX3 have been implicated in lateral root (LR) development as well as apical hook formation whereas both AUX1 and LAX1 and possibly LAX2 are required for leaf phyllotactic patterning.

View Article: PubMed Central - PubMed

Affiliation: School of Biosciences and Centre for Plant Integrative Biology, University of Nottingham Loughborough, UK.

ABSTRACT
Auxin regulates several aspects of plant growth and development. Auxin is unique among plant hormones for exhibiting polar transport. Indole-3-acetic acid (IAA), the major form of auxin in higher plants, is a weak acid and its intercellular movement is facilitated by auxin influx and efflux carriers. Polarity of auxin movement is provided by asymmetric localization of auxin carriers (mainly PIN efflux carriers). PIN-FORMED (PIN) and P-GLYCOPROTEIN (PGP) family of proteins are major auxin efflux carriers whereas AUXIN1/LIKE-AUX1 (AUX/LAX) are major auxin influx carriers. Genetic and biochemical evidence show that each member of the AUX/LAX family is a functional auxin influx carrier and mediate auxin related developmental programmes in different organs and tissues. Of the four AUX/LAX genes, AUX1 regulates root gravitropism, root hair development and leaf phyllotaxy whereas LAX2 regulates vascular development in cotyledons. Both AUX1 and LAX3 have been implicated in lateral root (LR) development as well as apical hook formation whereas both AUX1 and LAX1 and possibly LAX2 are required for leaf phyllotactic patterning.

No MeSH data available.


Related in: MedlinePlus