Characterization of GA20ox genes in tall and dwarf types coconut (Cocos nucifera L.)
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Coconuts (Cocos nucifera L.) are divided by the height into tall and dwarf types. In many plants the short phenotype was emerged by mutation of the GA20ox gene encoding the enzyme involved in gibberellin (GA) biosynthesis. Two CnGA20ox genes, CnGA20ox1 and CnGA20ox2, were cloned from tall and dwarf types coconut. The sequences, gene structures and expressions were compared. The structure of each gene comprised three exons and two introns. The CnGA20ox1 and CnGA20ox2 genes consisted of the coding region of 1110 and 1131 bp, encoding proteins of 369 and 376 amino acids, respectively. Their amino acid sequences are highly homologous to GA20ox1 and GA20ox2 genes of Elaeis guineensis, but only 57% homologous to each other. However, the characteristic amino acids two histidines and one aspartic acid which are the two iron (Fe2+) binding residues, and arginine and serine which are the substrate binding residues of the dioxygenase enzyme in the 20G-FeII_Oxy domain involved in GA biosynthesis, were found in the active site of both enzymes. The evolutionary relationship of their proteins revealed three clusters in vascular plants, with two subgroups in dicots and three subgroups in monocots. This result confirmed that CnGA20ox was present as multi-copy genes, and at least two groups CnGA20ox1 and CnGA20ox2 were found in coconut. The nucleotide sequences of CnGA20ox1 gene in both coconut types were identical but its expression was about three folds higher in the leaves of tall coconut than in those of dwarf type which was in good agreement with their height. In contrast, the nucleotide sequences of CnGA20ox2 gene in the two coconut types were different, but the expression of CnGA20ox2 gene could not be detected in either coconut type. The promoter region of CnGA20ox1 gene was cloned, and the core promoter sequences and various cis-elements were found. The CnGA20ox1 gene should be responsible for the height in coconut, which is different from other plants because no mutation was present in CnGA20ox1 gene of dwarf type coconut.
KeywordsGA biosynthesis gene Gene expression Promoter analysis Short stature
We are very grateful to Amara Thongpan for valuable discussions. This work was financially supported by Kasetsart University Research and Development Institute (KURDI), Kasetsart University, Thailand. The first author (T. B.) received the DPST (Development and Promotion of Science and Technology Talents) scholarship from IPST (The Institute for the Promotion of Teaching Science and Technology). We also thank the Chumphon Horticultural Research Center, Chumphon Province, Thailand for providing coconut samples.
Compliance with ethical standards
Conflict of interest
All the authors, T. Boonkaew, C. Mongkolsiriwatana, A. Vongvanrungruang, K. Srikulnath and S. Peyachoknagul, declare that they have no conflict of interest.
Research involving human and animal rights
This article does not contain any studies with human subjects or animals performed by any of the authors.
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