PT  - JOURNAL ARTICLE
AU  - Siamsa M. Doyle
AU  - Adeline Rigal
AU  - Peter Grones
AU  - Michal Karady
AU  - Deepak K. Barange
AU  - Mateusz Majda
AU  - Barbora Pařízková
AU  - Michael Karampelias
AU  - Marta Zwiewka
AU  - Aleš Pěnčik
AU  - Fredrik Almqvist
AU  - Karin Ljung
AU  - Ondřej Novák
AU  - Stéphanie Robert
TI  - A role for the auxin precursor anthranilic acid in root gravitropism via regulation of PIN-FORMED protein polarity and relocalization in <em>Arabidopsis</em>
AID  - 10.1101/422733
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 422733
4099  - http://biorxiv.org/content/early/2019/04/25/422733.short
4100  - http://biorxiv.org/content/early/2019/04/25/422733.full
AB  - Distribution of auxin within plant tissues is of great importance for developmental plasticity, including root gravitropic growth. Auxin flow is directed by the subcellular polar distribution and dynamic relocalization of auxin transporters such as the PIN-FORMED (PIN) efflux carriers, which can be influenced by the main natural plant auxin indole-3-acetic acid (IAA). Anthranilic acid (AA) is an important early precursor of IAA and previously published studies with AA analogues suggested that AA may also regulate PIN localization.Using Arabidopsis thaliana as a model species, we studied an AA-deficient mutant displaying agravitropic root growth, treated seedlings with AA and AA analogues and transformed lines to over-produce AA while inhibiting its conversion to downstream IAA precursors.We showed that AA rescues root gravitropic growth in the AA-deficient mutant at concentrations that do not rescue IAA levels. Overproduction of AA affects root gravitropism without affecting IAA levels. Treatments with, or deficiency in, AA result in defects in PIN polarity and gravistimulus-induced PIN relocalization in root cells.Our results reveal a previously unknown role for AA in the regulation of PIN subcellular localization and dynamics involved in root gravitropism, which is independent of its better-known role in IAA biosynthesis.