A Proposed Regulatory Mechanism of Ontogenetically Expressed DITAA-Containing Coconut Transcripts
Marni E. Cueno* and Rita P. Laude
Institute of Biological Sciences, College of Arts and Sciences (CAS),
University of the Philippines Los Baños (UPLB), College, Laguna 4031
Accumulation of medium-chain oils into the coconut endosperm has been shown to follow a temporal pattern of fatty acid gene expression. The mechanism by which these genes are regulated, however, has not been explored. Using 3’ RACE, we identified two coconut DITAA-containing transcripts (DCTs), appropriately labeled DCT1 and DCT2, and found both transcripts in the 5-6 and 6-7 month old (mo) coconut endosperms following an ontogenetic pattern. Comparison of both amplified transcripts from the 5-6 and 6-7 mo endosperms show 100% homology between DCT2 transcripts. Interestingly, 52 nt downstream of the DCT1 sequences prior to the poly(A) tail are missing in the DCT1-6mo transcript. Visual inspection for potential motifs shows the presence of CCGCC-like (DCT1-5mo and DCT1-6mo) and TGTG-like (DCT1-6mo only) motifs. Both motifs have been published to be known regulatory motifs in other species suggesting a probable similar function in coconut.
Coconut (Cocos nucifera L.) has often been considered the “tree of life” due to its several end products used in food, structure materials, and decorative items (Banzon and Velasco 1982). Coconut is the major export crop of the Philippines due to its oil (Harries 1994) and, at the moment, it is either exported as copra or as virgin coconut oil. Coconut oil is predominantly composed of lauric acids and the coconut’s lauric oil content commands a premium price in world markets (Banzon & Velasco 1982; Harries 1994), wherein, coconut (from the Philippines) and palm kernel (from Malaysia) are the major sources of lauric acid-rich vegetable oils with 48.2% and 50.9%, respectively (Banzon & Velasco 1982). Lauric oils represent about 6% (4.4 million metric tons) of the 72.7 million tons of the world’s oil and fats production, and 5.5% of the world’s total fats and oils consumption (Harries 1994).
It was previously suggested from the work of Villalobos et al. (2001) that coconut fatty acid synthesis follows an ontogenetic pattern of expression, however, it has never been proven to date. Moreover, as the solid endosperm . . . . . . . . .
BANZON JA, VELASCO JR. 1982. Coconut: production and utilization. Pasig, Metro Manila: Philippines: Philippine Coconut Research and Development Foundation, Inc. (PCRDF). p. 290-305.
BARREAU C, PAILLARD L, OSBORNE HB 2006. AUrich elements and associated factors: are there unifying principles? Nucleic Acids Research 33(22): 7138-50.
BEELMAN CA, PARKER R. 1995. Degradation of mRNA in eukaryotes. Cell 81(2): 179-183.
CUENO ME, LAUDE RP, LAURENA AC. 2010. Sequence analyses of the coconut enolase 3’end reveals a CACTG motif found within the 3’-untranslated region. Philippine Journal of Science 139(2): 227-232.
HARRIES HC. 1994. The coconut palm and its importance. Coconuts 11(1): 5-11.
IENGAR P, JOSHI NV. 2009. Identification of putative regulatory motifs in the upstream regions of coexpressed functional groups of genes in Plasmodium falciparum. BMC Genomics 10:18 DOI:10.1186/1471- 2164-10-18.
JACKSON RJ, STANDART N. 1990. Do the poly(A) tail and 3’ untranslated region control mRNA translation. Cell 62: 15-24.
MAZUMDER B, SESHADRI V, FOX PL. 2003. Translational control by the 3’-UTR: the ends specify the means. Trends in Biochemical Sciences 28(2): 91-98.
PESOLE G, GRILLO G, LARIZZA A, LIUNI S. 2000. The untranslated regions of eukaryotic mRNAs: Structure, function, evolution and bioinformatic tools for their analysis. Briefings in Bioinformatics 1(3): 236-249.
ROTHNIE HM. 1996. Plant mRNA 3’-end formation. Plant Molecular Biology 32: 43-61.
SACHS A, WHALE E. 1993. Poly (A) tail metabolism and function in eukaryotes. J Biol Chem 268: 22955-58.
SIGGAARD-ANDERSON M.1993. Protein Seq. Data Anal 5: 325-335.
SLABAUGH MB, TAI H, JAWORSKI JG, KNAPP S.1995. cDNA clones encoding beta-ketoacyl-acyl carrier protein synthase III from Cuphea wrightii. Plant Physiol 108: 443-444.
TAI H, JAWORSKI JG. 1993. 3-ketoacyl-acyl carrier protein synthase III from spinach (Spinacia oleracea) is not similar to other condensing enzymes of fatty acid synthase. Plant Physiol 103: 1361-67.
TAI H, POST-BEITTENMILLER D, JAWORSKI JG.1994. Cloning of a cDNA encoding 3-ketoacyl-acyl carrier protein synthase III from Arabidopsis. Plant Physiol 106: 801-802.
TSUGE M, HAMAMOTO R, SILVA FP, OHNISHI Y, CHAYAMA K, KAMATANI N, FURUKAWA Y, NAKAMURA Y. 2005. A variable number of tandem repeats polymorphism in an E2F-1 binding element in the 5’ flanking region of SMYD3 is a risk factor for human cancers. Nat Genet 37: 1104-07.
VILLALOBOS AL, DODDS PF, HORNUNG R. 2001. Changes in fatty acid composition during development of tissues of coconut (Cocos nufera L.) embryos in the intact and in vitro. Journal of Experimental Botany 52(358): 933-942.