Acyl-CoA-binding protein family members in laticifers are possibly involved in lipid and latex metabolism of Hevea brasiliensis (the Para rubber tree)

Abstract

BackgroundAcyl-CoA-binding proteins (ACBPs) are mainly involved in acyl-CoA ester binding and trafficking in eukaryotic cells, and their various functions have been characterized in model plants, such as Arabidopsis thaliana (A. thaliana), Oryza sativa (rice), and other plant species. In the present study, genome-wide mining and expression analysis of ACBP genes was performed on Hevea brasiliensis (the para rubber tree), the most important latex-producing crop in the world.ResultsSix members of the H. brasiliensis ACBP family genes, designated HbACBP1-HbACBP6, were identified from the H. brasiliensis genome. They can be categorized into four classes with different amino acid sequences and domain structures based on the categorization of their A. thaliana counterparts. Phylogenetic analysis shows that the HbACBPs were clustered with those of other closely related species, such as Manihot esculenta, Ricinus communis, and Jatropha carcas, but were further from those of A. thaliana, a distantly related species. Expression analysis demonstrated that the HbACBP1 and HbACBP2 genes are more prominently expressed in H. brasiliensis latex, and their expression can be significantly enhanced by bark tapping (a mechanical wound) and jasmonic acid stimulation, whereas HbACBP3-HbACBP6 had almost the same expression patterns with relatively high levels in mature leaves and male flowers, but a markedly low abundance in the latex. HbACBP1 and HbACBP2 may have crucial roles in lipid and latex metabolism in laticifers, so their subcellular location was further investigated and the results indicated that HbACBP1 is a cytosol protein, whereas HbACBP2 is an endoplasmic reticulum-associated ACBP.ConclusionsIn this study, the H. brasiliensis ACBP family genes were identified. Phylogenetic analyses of the HbABCPs indicate that there is a high conservation and evolutionary relationship between ACBPs in land plants. The HbACBPs are organ/tissue-specifically expressed and have different expression patterns in response to stimulation by bark tapping or ethrel/jasmonic acid. HbACBP1 and HbACBP2 are two important latex ACBPs that might be involved in the lipid and latex metabolism. The results may provide valuable information for further investigations into the biological functions of HbACBPs during latex metabolism and stress responses in H. brasiliensis.Electronic supplementary materialThe online version of this article (10.1186/s12864-017-4419-6) contains supplementary material, which is available to authorized users.

Advances in Understanding the Acyl-CoA-Binding Protein in Plants, Mammals, Yeast, and Filamentous Fungi

“…The results showed that bark tapping and JA stimulation increased the expression levels of HbACBP1 and HbACBP2, whereas ET only increased the expression level of HbACBP1 [10]. ET and bark tapping can promote the production of latex [27,28], and JA stimulation can promote laticifer differentiation [29], indicating that HbACBP1 and HbACBP2 play important roles in latex formation and lipid metabolism [10]. Therefore, as an important commercial resource, it is of great significance to explore the role of ACBP family proteins during the formation of latex.…”

“…The third class is a large molecular weight ACBP that has a single ACBP domain, which is usually composed of 215-700 amino acids. The fourth category is the kelch motif ACBP, which typically consists of 648 to 668 amino acids and contains a kelch domain at the C-terminus along with the ACBP domain [10,20]. In addition to the kelch domain and the ANK domain, ACBP family proteins in humans and mammals also contain different numbers of the ECH domain, GOLD domain, and Herpes DNAp domain [15].…”

“…The expression patterns of ACBP family proteins in laticifers were analyzed using three methods: bark tapping (a mechanical ground), exogeneous ethrel (ET, a releaser of ethylene), and jasmonic acid (JA) stimulation. The results showed that bark tapping and JA stimulation increased the expression levels of HbACBP1 and HbACBP2, whereas ET only increased the expression level of HbACBP1 [10]. ET and bark tapping can promote the production of latex [27,28], and JA stimulation can promote laticifer differentiation [29], indicating that HbACBP1 and HbACBP2 play important roles in latex formation and lipid metabolism [10].…”

“…For example, HbACBP1 and HbACBP2 play an important role in latex production and lipid metabolism. However, the specific mechanism during the formation of latex by H. brasiliensis is still unclear and needs to be further explored [10]. Latex as an important commercial resource [26]; therefore, exploring the mechanism of HbACBP in latex formation lays an important foundation for developing high-quality latex and increasing latex production.…”

“…By knocking out ACBP in mice, researchers found that the content of ceramide in the hepatocytes of mutant mice decreased significantly [9]. Recent studies have shown that there are six ACBP family proteins in Hevea brasiliensis, among which HbACBP1 and HbACBP2 play an important role during lipid metabolism and latex synthesis [10].…”