Isolation and Characterization of a GS2 Gene in Melon (Cucumis melo L.) and its Expression Patterns under the Fertilization of Different Forms of N

• Published in: Molecular biotechnology 2010, Vol.44 (1), p.51-60
• Main Authors: Deng, Yang-Wu, Zhang, Yi-Dong, Chen, Yi, Wang, Shu, Tang, Dong-Mei, Huang, Dan-Feng
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Ammonium; Biochemistry; Biological and medical sciences; Biological Techniques; Biotechnology; Botany; Cell Biology; Chemistry; Chemistry and Materials Science; Cloning; Cucumis melo - drug effects; Cucumis melo - enzymology; Cucumis melo - genetics; Dose-Response Relationship, Drug; Enzymes; Fruits; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant - drug effects; Gene Expression Regulation, Plant - physiology; Genetics; Glutamate-Ammonia Ligase - chemistry; Glutamate-Ammonia Ligase - genetics; Glutamate-Ammonia Ligase - metabolism; Human Genetics; Leaves; Molecular biology; Molecular Sequence Data; Nitrogen - administration & dosage; Protein Science
• ISSN: 1073-6085; 1559-0305
• DOI: 10.1007/s12033-009-9203-7

We isolated a novel glutamine synthetase (GS, EC 6.3.1.2) gene M-GS2 (accession: AY773090) by the RACE approach from melon. The full-length cDNA of M-GS2 is 1807 bp and contains a 1296 bp open reading frame (ORF) encoding 432 amino acids. The deduced protein contains conserved structural domains among plant GS2 proteins and shares extensive sequence homology with GS2 enzymes from other higher plants. M-GS2 expresses with specificity in leaf, and identification of a chloroplast transit peptide (cTP) in M-GS2 suggests that it localizes to the chloroplast. As shown by real-time quantitative PCR, distinct forms of nitrogen (N) found in fertilizers transcriptionally regulated M-GS2 differently. Ammonium and nitrate feeding only significantly regulated M-GS2 transcripts in leaf; starving (0.75 mM) or moderate (3.75 mM) N levels dramatically increased M-GS2 transcripts for 1 day, decreasing to a constant low level after 2-3 days, while sufficient N level (7.5 mM) had a minor effect throughout 3 days compared to controls. Glutamate feeding, however, not only significantly regulated M-GS2 transcripts in leaf (decreased initially then increased to higher levels than controls), but also in root, where it was up-regulated continuously. Our results suggested that M-GS2 is the first GS gene cloned and characterized in melon and melon responds to the variations in N fertilization by differentially expressing M-GS2.