The Philippines Lono Tall (PLT) coconut, which is a Laguna Tall (LAGT) endosperm variant, possesses immense potential for the coconut oil industry due to its high oil content, although its unusually low fruit setting make it unsuitable for intercrossing. To understand the differences that govern fatty acid and oil accumulation in PLT and LAGT endosperms, 6-7 month-old endosperm transcripts were generated and compared through RNA-Seq. Three WRINKLED1 (WRI1) paralogs were identified, wherein AP2/EREBP-WRI1 was highly transcribed during oil accumulation in PLT. The higher levels of lauric acid in PLT coincided with the upregulation of a PALMITOYL ACYL-ACYL CARRIER PROTEIN THIOESTERASE (FatB) paralog and three LYSOPHOSPHATIDIC ACID ACYLTRANSFERASE (LPAAT) paralogs. The upregulation of oleosins (OLE) in PLT concurs with the higher oil content found in its endosperm when compared to LAGT. Transcript expression verified through qRT-PCR of four OLE paralogs across endosperm developmental stages revealed that the upregulation of OLE5 might account for the significantly higher amounts of oil deposition in PLT. Transcript activities of ELONGATION OF FATTY ACIDS 3 (ELO3), and DELTA(8)-FATTY ACID DESATURASE 2 (d8-DES2) implies that the peak of medium-chain fatty acid accumulation and desaturation occurs earlier (6 months after pollination) in PLT than in LAGT (8 months after pollination). The lower levels of transcription of these two genes agree with the observed lower amounts of unsaturated fatty acids in PLT.
