Abstract
ABSTRACTPhytohormone auxin plays an indispensable role in the plethora of plant developmental process starting from the cell division, and cell elongation to morphogenesis. Auxins are transported to different parts of the plant by different sophisticated transporter molecules known as ‘auxin transporters’.There are four auxin transporter families that have been reported so far in the plant kingdom which includes AUX/LAX (AUXIN-RESISTANT1–LIKES), PIN (PIN-FORMED, auxin efflux carriers), ABCB ((ATP-binding cassette-B (ABCB)/P-glycoprotein (PGP)) and PILS (PIN-Likes). Auxin influx and efflux carriers are distributed in a polar fashion in the plasma membrane whereas ABCB and PILS are present in a non-polar fashion. Other than AUX/LAX, other auxin transporters harbor N-and C-terminal conserved domains along with a variable hydrophilic loop in the transmembrane domain. The AUX/LAX, ABCB and PIN transporters mediate long distance auxin transport whereas PILS and PIN5 protein involved in intracellular auxin homeostasis.
Highlights
Auxin is one of the most important plant hormone that plays diverse roles in plants, starting from the cell division, differentiation and it’s expansion to morphogenesis, organogenesis and vascular differentiation
It has been seen that AUX/LAX auxin transporter homologs are present throughout the plant kingdom and they may have evolved before the evolution of the land plants as AUX/LAX-like sequences were reported in several unicellular and colony forming Chlorophyta as well (De Smet et al 2011; Swarup and Péret 2012)
Brefeldin A, a fungal toxin is the classic example of auxin response factor (ARF) inhibitor that inhibits the internal trafficking of AUX1 and leads to the disappearance of PIN proteins from the plasma membrane (Shevell et al 1994; Kleine-Vehn et al 2006)
Summary
Auxin is one of the most important plant hormone that plays diverse roles in plants, starting from the cell division, differentiation and it’s expansion to morphogenesis, organogenesis and vascular differentiation. The study of auxin biology dates back to the Darwinian era (1880) when Charles Darwin along with his son Francis Darwin performed the famous coleoptile experiments and reported about the movement of plants in response to an unknown factor ‘influence’. They conducted this study in more than 40 plant species and described their findings in the book entitled ‘The Power of Movement in Plants’ (1881). The unknown factor was later named as ‘auxin’ They predicted that auxin flow was basipetal i-e. In recent times the auxin transport research has gained considerable attention and lots of advancements have been made in this field and the role of auxin transporters in plant development has been dissected extensively at the cellular and molecular levels, which will be the focus of this review
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