Poster: Tropisms

Abs # 407: The tt4 mutation prevents flavonoid synthesis and alters auxin transport and the response of arabidopsis roots to gravity and light

Presenter:	Muday, Gloria K, muday@wfu.edu
Authors	Muday, Gloria K (A)   Buer, Charles  (A)
Affiliations:	(A): Wake Forest University

We examined whether flavonoids act as endogenous auxin transport regulators during gravity vector and light intensity changes in Arabidopsis thaliana roots. Flavonoid deficient tt4(2YY6) seedlings had elevated root basipetal auxin transport compared to wild type, consistent with the absence of a negative auxin transport regulator. The tt4(2YY6) roots had delayed gravitropism that was chemically complemented with a flavonoid intermediate. Flavonoid accumulation was found in wild-type columella cells, the site of gravity perception, and in epidermal and cortical cells, the site of differential growth, but flavonoid accumulation is absent in tt4(2YY6) roots. Flavonoid accumulation was higher in gravity stimulated root tips, as compared to vertical controls, with maximal differences coinciding with the timing of gravitropic bending. Flavonoid accumulation was also elevated by exogenous IAA suggesting that flavonoid changes in response to gravity might be due in part to changing IAA distribution. Acropetal IAA transport was also elevated in tt4(2YY6). Flavonoid synthesis was repressed by dark, as were differences in acropetal transport in tt4(2YY6). These results are consistent with light- and gravity-induced flavonoid stimulation that alters auxin transport in roots and dependent physiological processes, including gravitropic bending and root development.