Untitled

Abstract

The first committed step in the beta-oxidation of fatty acids is catalyzed by the enzyme acyl-CoA oxidase (ACOX), which oxidizes a fatty acyl-CoA to a 2-trans-enoyl-CoA. To understand the role of beta-oxidation during seedling growth in soybean, two ACOX cDNAs were isolated by screening a seedling library with a DNA fragment obtained by RT-PCR by using degenerate oligonucleotides. The two cDNAs (ACX1;1 and ACX1;2) are 86% identical to each other at the nucleotide and the amino acid level. Their deduced amino acid sequences share significant homology with known acyl-CoA oxidases, including the conserved CGGHGY motif, a putative flavin mononucleotide binding site. In both sequences, the last three amino acids, ARL, represent a putative peroxisome targeting signal. The mRNA and protein of both cDNAs accumulated in all seedling tissues, with relatively stronger expression in the growing seedling axis and hypocotyl, and weaker expression in the cotyledon. Immunolocalization studies indicated that the two proteins were localized in the phloem cells of hypocotyl tissue. The two cDNAs were expressed in Escherichia coli and shown to possess acyl-CoA oxidase activity. With fatty acyl-CoA substrates of varying chain lengths, it was demonstrated that both ACX1;1 and ACX1;2 have broad substrate specificities (C8-C18). The stronger expression of ACX1;1 and ACX 1;2 in the axis and hypocotyl tissue, the weaker expression in the oil-rich cotyledon tissue, and the broad substrate specificities suggest that the two acyl-CoA oxidases might play a general house-keeping role during soybean seedling growth, such as the turnover of membrane lipids.

Quantitative proteomic analysis of auxin signaling during seedling development

“…Amino acid metabolism was a common category observed among all the datasets (Figure 4), which is consistent with several recently described links between Target of rapamycin (TOR) and auxin Deng et al, 2016;Li et al, 2017;Pu et al, 2017;Salem et al, 2017). Proteins associated with lipid metabolism were differentially regulated in hypocotyls, roots and seedlings at all time points, including well characterized acyl-Co-A oxidase (ACX) enzymes that play roles in auxin mediated growth (Adham et al, 2005;Agarwal et al, 2001), suggesting that changes in lipid composition may underlie auxin driven growth processes.…”

Mutation of ACX1, a Jasmonic Acid Biosynthetic Enzyme, Leads to Petal Degeneration in Chinese Cabbage (Brassica campestris ssp. pekinensis)

“…In tomato, a single point mutation of LeACX1 resulted in the deficiency of JA production and compromised in its wound response [48]. Two acyl-CoA oxidases in soybean ( ACX1;1 and ACX1;2 ) had relatively stronger expression in the growing seedling axis and hypocotyl and weaker expression in the cotyledon [40]. Herbivore-induced acyl coenzyme gene CsACX1 is involved in the synthesis of JA and expressed during the flowering in tea plants ( Camellia sinensis ) [41].…”

“…Acyl-CoA oxidase (ACX) is the first and the key step controlling enzyme involved in fatty acid β-oxidation. ACX1 orthologs have been extensively studied in many plant species, mainly including tomato ( Lycopersicon esculentum ), Arabidopsis , soybean ( Glycine max ), and tea ( Camellia sinensis ) [38,39,40,41].…”