High impact information on ASA1

• Upregulation of WEI2/ASA1 and WEI7/ASB1 by ethylene results in the accumulation of auxin in the tip of primary root, whereas loss-of-function mutations in these genes prevent the ethylene-mediated auxin increase [1].
• This study provides a mechanistic explanation for the root-specific ethylene insensitivity of wei2 and wei7, illustrating how interactions between hormones can be used to achieve response specificity [1].
• Whereas ASA2 is expressed at a constitutive basal level, ASA1 is induced by wounding and bacterial pathogen infiltration, suggesting a novel role for ASA1 in the production of tryptophan pathway metabolites as part of an Arabidopsis defense response [2].
• Arabidopsis thaliana has two genes, ASA1 and ASA2, encoding the alpha subunit of anthranilate synthase, the enzyme catalyzing the first reaction in the tryptophan biosynthetic pathway [2].
• Characterization of rice anthranilate synthase alpha-subunit genes OASA1 and OASA2. Tryptophan accumulation in transgenic rice expressing a feedback-insensitive mutant of OASA1 [3].

Biological context of ASA1

• The mutant also showed cross-resistance to 5-methylanthranilate and 6-methylanthranilate and mapped to chromosome V at or close to ASA1 (a gene encoding the AS alpha subunit) [4].
• A novel mutation in the anthranilate synthase alpha 1 (ASA1) gene, named trp5-2wvc1, and mutations in the tryptophan synthase alpha and beta 1 genes (trp3-1 and trp2-1, respectively) confer a compressed root wave phenotype on tilted agar surfaces [5].
• Sequencing of the ASA1 gene from amt-1 revealed a G to A transition relative to the wild-type gene that would result in the substitution of an asparagine residue in place of aspartic acid at position 341 in the predicted amino acid sequence of the ASA1 protein [4].
• The metabolic effects of expressing the feedback-resistant anthranilate synthase alpha subunit were also dramatic [6].

Associations of ASA1 with chemical compounds

• Together, these findings reveal that ASA1 and ASB1 are key elements in the regulation of auxin production and an unexpected node of interaction between ethylene responses and auxin biosynthesis in Arabidopsis [1].
• Concurrently, tryptamine levels increase up to 9-fold in the induced trp5:ASB1 line (specific yield ca. 1.9 mg g(-1) dry weight) as compared with only a 4-fold tryptamine increase in the induced trp5 line (specific yield ca. 0.3 mg g(-1) dry weight) [7].
• Metabolic changes in transgenic Arabidopsis plants expressing the feedback-resistant anthranilate synthase alpha subunit gene OASA1D were investigated with respect to Trp synthesis and effects on secondary metabolism [8].
• In an attempt to more successfully engineer the indole pathway, a wild type Arabidopsis ASbeta subunit (ASB1) cDNA was constitutively expressed along with the inducible expression of trp5 and TDC in C. roseus hairy roots [7].

Regulatory relationships of ASA1

• Recently we successfully expressed Arabidopsis genes encoding a feedback-insensitive anthranilate synthase alpha subunit under the control of the glucocorticoid-inducible promoter system and the anthranilate synthase beta subunit under the control of a constitutive promoter in C. roseus hairy roots [9].

Other interactions of ASA1

• The level of immunologically detectable anthranilate synthase alpha subunit protein is increased in the trp2 mutants, suggesting the possibility of regulation of anthranilate synthase levels in response to tryptophan limitation [10].

References