The ArabidopsisTUMOR PRONE5Gene Encodes an Acetylornithine Aminotransferase Required for Arginine Biosynthesis and Root Meristem Maintenance in Blue Light      

Abstract

Arginine is an essential amino acid necessary for protein synthesis and is also a nitrogen storage compound. The genes encoding the enzymes of arginine biosynthesis in plants are not well characterized and have mainly been predicted from homologies to bacterial and fungal genes. We report the cloning and characterization of the TUMOR PRONE5 (TUP5) gene of Arabidopsis (Arabidopsis thaliana) encoding an acetylornithine aminotransferase (ACOAT), catalyzing the fourth step of arginine biosynthesis. The free arginine content was strongly reduced in the chemically induced recessive mutant tup5-1, root growth was restored by supplementation with arginine and its metabolic precursors, and a yeast (Saccharomyces cerevisiae) ACOAT mutant was complemented by TUP5. Two null alleles of TUP5 caused a reduced viability of gametes and embryo lethality, possibly caused by insufficient Arg supply from maternal tissue. TUP5 expression is positively regulated by light, and a TUP5-green fluorescent protein was localized in chloroplasts. tup5-1 has a unique light-dependent short root phenotype. Roots of light-grown tup5-1 seedlings switch from indeterminate growth to determinate growth with arresting cell production and an exhausted root apical meristem. The inhibitory activity was specific for blue light, and the inhibiting light was perceived by the root. Thus, tup5-1 reveals a novel role of amino acids and blue light in regulating root meristem function.

Quantitative proteome-level analysis of paulownia witches’ broom disease with methyl methane sulfonate assistance reveals diverse metabolic changes during the infection and recovery processes

“…Arginine is an essential amino acid for protein synthesis, and it is also a nitrogen storage compound (Fremont et al, 2013). After phytoplasma infections, arginine production is induced by accumulated ArgD, indicating that protein synthesis might be stimulated by PaWB.…”

Normal root elongation requires arginine produced by argininosuccinate lyase in rice

“…Interestingly, mutation of argininosuccinate lyase did not affect the free arginine concentration in the roots, but increased the concentration of asparagine and glutamine (Figure ). Over‐accumulation of asparagine and glutamine is consistent with that observed in the Arabidopsis tup5‐1 mutant (Frémont et al ., ). However, different from tup5‐1 mutant, no difference in the free arginine level was found in the rice roots between the osred1 mutant and the wild type (Figure ).…”

“…Our results showed that arginine seems especially important for transverse cell division activity in roots (Figure 2a-g). Recently, a study with Arabidopsis also showed that TUMOR PRONE5 (TUP5), encoding an acetyl-Orn aminotransferase involved in the fourth step in arginine biosynthesis, is implicated in sustaining root growth and development under blue light (Fr emont et al, 2013). Knockout of TUP5 resulted in short roots and this phenotype could be recovered with addition of arginine to the medium.…”

“…One possibility is that the difference may exist in the root tip, but OsALS1 is expressed in all root cells including the root tip and the mature zone (Figures 7 and 8), therefore this possibility seems unlikely. The arginine level in the roots is fine-tuned and kept at a low level by the metabolic control system (Fr emont et al, 2013). In fact, the free arginine level in wild-type rice is very low (Figure 10).…”

“…The Arabidopsis gapcp double mutant, which has a reduced amount of serine in comparison with the wild type, displayed a defect in primary root growth (Muñoz-Bertomeu et al, 2009). Recently, another Arabidopsis mutant, tup5, which bears a defect in the biosynthesis of arginine, was shown to have a strongly reduced free arginine content, resulting in a short-root phenotype (Fr emont et al, 2013).…”