Effects of Glutamine on Vitamin B6 Biosynthesis in Arabidopsis thaliana
Date Issued
2016
Date
2016
Author(s)
Lin, Sang-Chu
Abstract
Glutamine is one of the most abundant free amino acids in plants. As the first organic nitrogen from primary nitrogen assimilation, glutamine is a major amino donor for the synthesis of amino acids, nucleotides, and other nitrogen-containing compounds. We showed that glutamine could efficiently support Arabidopsis growth when used as a sole nitrogen source in the growth medium, but the addition of excess glutamine significantly inhibited Arabidopsis growth. We thus used appropriate glutamine concentration as sole nitrogen source to screen for “glutamine hypersensitive” mutants. One of the mutants, line 23844/pdx3-3, had dramatically reduced root growth, irregular cell arrangement, less cell proliferation and abnormal cell death in glutamine-containing medium. Line 23844 is defective in At5g49970 that encodes pyridoxine/ pyridoxamine phosphate oxidase (PDX3) of the vitamin B6 salvage pathway. The mutant has a point mutation that changes Gln226 to a stop codon. In addition to the mutant, we have obtained the genetic complementation line and PDX3 gene silencing lines that show similar phenotypes. These results suggested that the growth defects in 23844 are caused by loss-of-function in the PDX3 gene. sos4 (salt overly sensitive 4), another mutant involved in vitamin B6 salvage pathway, had similar phenotypes with pdx3-3, and pdx3-3/sos4 double mutant had more severe phenotypes. Furthermore, by analysis vitamin B6 contents in pdx3-3 and sos4, we found abnormal vitamin B6 levels in mutants. These data indicated that defects in vitamin B6 salvage pathway might result in glutamine hypersensitive phenotypes. Nevertheless, the functions of PDX3 and the vitamin B6 salvage pathway are not well understood in plants. We will further study the relationship between glutamine and vitamin B6 salvage pathway, and the regulation of vitamin B6 homeostasis.
Subjects
Glutamine
vitamin B6 salvage pathway
Type
thesis
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