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Differential expression of selected genes in normal and mutant makapuno endosperms of coconut (Cocos nucifera L.) using relative RT-PCR
Dissertation Abstract:
Makapuno is an abnormal coconut with a characteristic solid endosperm overgrowth. To gain insights on the molecular explanation of the makapuno phenomenon, the cDNA sequence variation and transcript profile of selected genes were investigated in normal and mutant makapuno coconut solid endosperm at different stages of development. A total of 14 partial cDNAs were studied. Of these, eight genes, namely: two putative isoforms of α-D-galactosidase gene (Cnagal1 and Cnagal2), cytosolic glyceraldehyde-3-phosphate dehydrogenase (Cngap), cytosolic pyruvate kinase (Cnpk), enolase (Cneno), pyruvate decarboxylase (Cnpdc), and two putative isoforms of ketoacyl-ACP synthase I (Cnkas1-1 and Cnkas1-2) are involved in carbon metabolism. Two genes, arginine decarboxylase (Cnadc) and isopentenyl transferase (Cnipt), are for hormone biosynthesis. Four regulatory factors, namely: myb-like transcription factor (Cnmyb), poly(A)-binding protein (Cnpab), protein kinase CK2 beta chain (Cnckb), and eukaryotic initiation factor 4A (cneIF-4A) were also cloned These cDNAs harbor conserved domains and have 75–98 percent identity to other plant sequences. For all these genes, the makapuno and normal coconut endosperms have identical nucleotide and amino acid sequences. Expression analysis in normal coconut and makapuno solid endosperm using relative RT-PCR with actin as reference gene revealed four genes (Cnipt, Cngap, Cnpk, and Cneno) with lower expression in the makapuno. Genes which were unregulated in the makapuno include Cnpdc, Cnpab, Cnmyb, Cnagal1, Cnckb, and Cnkas1. The molecular characterization and expression profile of these genes provided new knowledge and further insights into the elucidation of the molecular mechanisms regulating gene expression in normal and mutant makapuno endosperms of coconut.