Jan 16, 2015

Identification of an Arabidopsis Aminotransferase that Facilitates Tryptophan and Auxin Homeostasis

BioRxiv : the Preprint Server for Biology
Michael PieckJohn Celenza

Abstract

IAA plays a critical role in regulating numerous aspects of plant growth and development. While there is much genetic support for tryptophan-dependent (Trp-D) IAA synthesis pathways, there is little genetic evidence for tryptophan-independent (Trp-I) IAA synthesis pathways. Using Arabidopsis, we identified two mutant alleles of ISS1 ( Indole Severe Sensitive ) that display indole-dependent IAA overproduction phenotypes including leaf epinasty and adventitious rooting. Stable isotope labeling showed that iss1 , but not WT, uses primarily Trp-I IAA synthesis when grown on indolesupplemented medium. In contrast, both iss1 and WT use primarily Trp-D IAA synthesis when grown on unsupplemented medium. iss1 seedlings produce 8-fold higher levels of IAA when grown on indole and surprisingly have a 174-fold increase in Trp. These findings indicate that the iss1 mutant’s increase in Trp-I IAA synthesis is due to a loss of Trp catabolism. ISS1 was identified as At1g80360, a predicted aromatic aminotransferase, and in vitro and in vivo analysis confirmed this activity. At1g80360 was previously shown to primarily carry out the conversion of indole-3-pyruvic acid to Trp as an IAA homeostatic mechanism in young seedlings. Our results suggest ...Continue Reading

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Mentioned in this Paper

Metabolic Process, Cellular
In Vivo
Biochemical Pathway
Tryptophan
Arabidopsis
Amino Acids, I.V. solution additive
Auxins
Catabolic Process
Aminotransferase Activity
indol-3-yl pyruvic acid

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