Rahman, Abidur , Bannigan, Alex , Sulaman, Waheeda , Pechter, Priit , Blancaflor, Elison , Baskin, Tobias .
Auxin, actin, and growth of the Arabidopsis thaliana primary root.
To understand how auxin regulates root growth, we quantified cell division, elemental elongation, and examined actin in the primary root of Arabidopsis thaliana . In treatments for 48 hours that inhibit root elongation rate by 50%, we find that auxins and auxin-transport inhibitors can be put into two classes based on their effects on cell division, elongation, and actin. Indoleacetic acid (IAA), 1-naphthalene acetic acid (NAA), and tri-iodobenzoic acid (TIBA) inhibit root growth primarily through reducing the length of the growth zone rather than the maximal rate of elemental elongation and they do not reduce cell production rate. These three compounds have little effect on the extent of filamentous actin, as imaged in living cells or with chemical fixation and immuno-cytochemistry, but tend to increase actin bundling. In contrast, 2,4-dichlorophenoxy-acetic acid (2,4-D) and naphthylphthalamic acid (NPA) inhibit root growth primarily by reducing cell production rate. These compounds remove actin, slow cytoplasmic streaming, yet do not lead to the mislocalization of the auxin-efflux proteins, PIN1 or PIN2. The effects of 2,4-D and NPA were mimicked by the actin inhibitor, latrunculin B. The effects of these compounds on actin were elicited with a 2 hour treatment at higher concentration but were not seen in two mutants, eir1-1 and aux1-7, with deficient auxin transport. Our results show that IAA regulates the size of the root elongation zone whereas 2,4-D affects cell production and actin-dependent processes; and further, that elemental elongation and localization of PINs are appreciably independent of actin.
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1 - Iwate University, Cryobiosystem Research Center, 3-18-8 Ueda, Morioka, Iwate, 020-8550, Japan
2 - Noble Foundation, Plant Biology Division
3 - University of Massachusetts, Biology Department
Presentation Type: ASPB Minisymposium
Location: Continental B/Hilton
Date: Tuesday, July 10th, 2007
Time: 4:10 PM