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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.


Auxin chemical properties and chemioosmotic hypothesis of auxin transport. The percentages of the anionic and protonated forms of IAA (indole acetic acid) are given as a funtion of pH with an emphasis on the apoplastic and cytosolic pH ranges (A). Chemiosmotic auxin transport model showing the different families of transporters: AUX/LAX, PIN, and PGP. The artificial form of auxin 1-NAA (1-Naphthalene acetic acid) is lipophilic and diffuses freely inside the cell (B).
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Figure 1: Auxin chemical properties and chemioosmotic hypothesis of auxin transport. The percentages of the anionic and protonated forms of IAA (indole acetic acid) are given as a funtion of pH with an emphasis on the apoplastic and cytosolic pH ranges (A). Chemiosmotic auxin transport model showing the different families of transporters: AUX/LAX, PIN, and PGP. The artificial form of auxin 1-NAA (1-Naphthalene acetic acid) is lipophilic and diffuses freely inside the cell (B).

Mentions: As per chemiosmotic polar diffusion hypothesis, the term first coined by Goldsmith (1977) based on the famous work of Rubery and Sheldrake (1974) and Raven (1975) cellular IAA movement is facilitated by combined activities of auxin influx and efflux carriers. IAA is a weak acid (pKa 4.75) and at mildly acidic apoplastic pH, only a small portion of IAA (IAAH ~15%) is able to passively diffuse inside the cell but the majority (85%) of IAA remains in its dissociated form (IAA−) and would require a carrier for its active uptake across the cell (Figure 1A). Inside the cell, at pH 7.0, all IAA remains in its polar IAA− form and would require auxin efflux carriers (Zazímalová et al., 2010). Chemiosmotic hypothesis also predicted that the polarity of auxin movement is provided by asymmetric localization of auxin carriers.


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

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

Auxin chemical properties and chemioosmotic hypothesis of auxin transport. The percentages of the anionic and protonated forms of IAA (indole acetic acid) are given as a funtion of pH with an emphasis on the apoplastic and cytosolic pH ranges (A). Chemiosmotic auxin transport model showing the different families of transporters: AUX/LAX, PIN, and PGP. The artificial form of auxin 1-NAA (1-Naphthalene acetic acid) is lipophilic and diffuses freely inside the cell (B).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: Auxin chemical properties and chemioosmotic hypothesis of auxin transport. The percentages of the anionic and protonated forms of IAA (indole acetic acid) are given as a funtion of pH with an emphasis on the apoplastic and cytosolic pH ranges (A). Chemiosmotic auxin transport model showing the different families of transporters: AUX/LAX, PIN, and PGP. The artificial form of auxin 1-NAA (1-Naphthalene acetic acid) is lipophilic and diffuses freely inside the cell (B).
Mentions: As per chemiosmotic polar diffusion hypothesis, the term first coined by Goldsmith (1977) based on the famous work of Rubery and Sheldrake (1974) and Raven (1975) cellular IAA movement is facilitated by combined activities of auxin influx and efflux carriers. IAA is a weak acid (pKa 4.75) and at mildly acidic apoplastic pH, only a small portion of IAA (IAAH ~15%) is able to passively diffuse inside the cell but the majority (85%) of IAA remains in its dissociated form (IAA−) and would require a carrier for its active uptake across the cell (Figure 1A). Inside the cell, at pH 7.0, all IAA remains in its polar IAA− form and would require auxin efflux carriers (Zazímalová et al., 2010). Chemiosmotic hypothesis also predicted that the polarity of auxin movement is provided by asymmetric localization of auxin carriers.

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.