Hormones, Polyamines, and Cell Wall Metabolism during Oil Palm Fruit Mesocarp Development and Ripening

Abstract

Oil palm is one of the most productive oil-producing crops and can store up to 90% oil in its fruit mesocarp. Oil palm fruit is a sessile drupe consisting of a fleshy mesocarp from which palm oil is extracted. Biochemical changes in the mesocarp cell walls, polyamines, and hormones at different ripening stages of oil palm fruits were studied, and the relationship between the structural and the biochemical metabolism of oil palm fruits during ripening is discussed. Time-course analysis of the changes in expression of polyamines, hormones, and cell-wall-related genes and metabolites provided insights into the complex processes and interactions involved in fruit development. Overall, a strong reduction in auxin-responsive gene expression was observed from 18 to 22 weeks after pollination. High polyamine concentrations coincided with fruit enlargement during lipid accumulation and latter stages of maturation. The trend of abscisic acid (ABA) concentration was concordant with GA₄ but opposite to the GA₃ profile such that as ABA levels increase the resulting elevated ABA/GA₃ ratio clearly coincides with maturation. Polygalacturonase, expansin, and actin gene expressions were also observed to increase during fruit maturation. The identification of the master regulators of these coordinated processes may allow screening for oil palm variants with altered ripening profiles.

Deciphering key proteins of oil palm (Elaeis guineensis Jacq.) fruit mesocarp development by proteomics and chemometrics

“…However, the dissimilar trend of the upregulated expression until 18 WAA prior to suddenly decreased at 20 WAA was observed in coatomer subunit delta‐2 (spot 1284) which involved in vesicle transport and 14‐3‐3 protein (spot 1364) in signalling. In a disagreement with the present results, the previous study has demonstrated the abundance of actin at 15 and 20 WAA while the gene expression level peaked at 12 and 14 WAA and remained high towards ripening coinciding with the cell expansion during lipid accumulation . The increase in actin during ripening corresponding to oil palm and berry development might be related to cell expansion during lipid accumulation due to involvement in several cellular processes such as cell shape determination, cytoplasmic streaming, extension growth and organelle movement .…”

“…However, the lignin content was triggered by higher lipid production in mesocarp tissues caused by the down‐regulation of the key enzyme in the lignin biosynthetic pathway i.e. caffeoyl CoA 3‐ O ‐methyltransferase (CCOMT) discordance with the upregulated of ROMT from our finding .…”

“…The principal component 1 (PC1) was 40% variance which explained the clustering of the samples by the early development phase (10, 12, 14, 15 and 16 WAA) and the ripening phase (18 and 20 WAA). The separation of oil palm fruit samples along the time gradient of development from PCA analysis corresponded to the comprehensive study of oil palm mesoderm in the course of fruit ripening . However, PC2 (10% variances) showed no significant difference between mesocarp stages or gel replicates.…”

“…Furthermore, chromoplast proteins which are necessary for most of the physiological processes such as fatty acid biosynthesis in oil palm mesocarp have been studied using proteomics approaches . Concurrently with transcriptome and proteome progress, metabolomics technology was also employed to profile oil palm mesocarp metabolites which reveals the biochemical changes in the cell wall, hormone, sugar, amino acid, organic acid, lipid, polyamine and nucleoside levels during fruit development as well as the correlation amongst structural and biochemical components during ripening .…”

Transcriptome Analysis of Cell Wall and NAC Domain Transcription Factor Genes during Elaeis guineensis Fruit Ripening: Evidence for Widespread Conservation within Monocot and Eudicot Lineages

“…That EgACO and EgPG4 share similar expression profiles with various cell wall modifying protein transcripts suggests ethylene may transcriptionally regulate cell wall activities differentially as proposed previously (Ireland et al, 2014). Previous work on cell wall related gene expression during oil palm mesocarp ripening monitored only very few genes (Teh et al, 2014). In contrast, the current work includes a more comprehensive analysis of 56 differentially expressed genes from at least 20 different cell wall related gene families.…”