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Distinct patterns of the histone marks associated with recruitment of the methionine chain-elongation pathway from leucine biosynthesis.

Xue M, Long J, Jiang Q, Wang M, Chen S, Pang Q, He Y - J. Exp. Bot. (2014)

Bottom Line: In general, genes involved in leucine biosynthesis were robustly associated with H3k4me2 and H3K4me3.This H3K4m3-depleted pattern had no effect on gene transcription, whereas it seemingly co-evolved with the entire pathway of aliphatic GLS biosynthesis.The results reveal a novel association of the epigenetic marks with plant secondary metabolism, and may help to understand the recruitment of the methionine chain-elongation pathway from leucine biosynthesis.

View Article: PubMed Central - PubMed

Affiliation: National Maize Improvement Center of China, Beijing Key Laboratory of Crop Genetic Improvement, China Agricultural University, Beijing 100193, China.

No MeSH data available.


Metabolic parallels between methionine chain elongation in aliphatic GLS (left) and the late steps of leucine biosynthesis (right). The dotted line indicates the repeated cycles to generate up to six methylene resdues. The genes specified in the methionine chain-elongation pathway are highlighted in red. In comparison, the genes functional in leucine biosynthetic pathway are highlighted in blue. The representative studies referring to the characterization of those genes are shown.
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Figure 1: Metabolic parallels between methionine chain elongation in aliphatic GLS (left) and the late steps of leucine biosynthesis (right). The dotted line indicates the repeated cycles to generate up to six methylene resdues. The genes specified in the methionine chain-elongation pathway are highlighted in red. In comparison, the genes functional in leucine biosynthetic pathway are highlighted in blue. The representative studies referring to the characterization of those genes are shown.

Mentions: The cycles of methionine chain elongation consist of four enzymatic steps, namely condensation, isomerization, oxidative decarboxylation, and deamination (Fig. 1). Interestingly, a similar cycle of 2-oxo acid-based chain-elongation reactions is also utilized in leucine biosynthesis. More importantly, genes participating in each step of the two pathways are evolutionary homologues (Fig. 1). At the condensation step, two methylthioalkylmalate synthases (MAM1 and MAM3) share ~60% amino acid identity with the two isopropylmalate synthases (IPMS1 and IPMS2) (Textor et al., 20042007; de Kraker et al., 2007). The isomerization step is catalysed by isopropylmalate isomerases (IPMIs), which exist as heterodimeric enzymes and each consists of a large subunit encoded by a single gene, named LeuC, and a small subunit encoded by one of three genes, named LeuD1, LeuD2, and LeuD3. LeuC has dual functions in both pathways, while the functions of different LeuD genes are diversified, with LeuD1 and LeuD2 functional in methionine chain elongation, whereas LeuD3 is functional in leucine biosynthesis (Knill et al., 2009; Sawada et al., 2009; He et al., 2010; Imhof et al., 2014). Similarly, in the oxidative decarboxylation step, isopropylmalate decarboxylase 1 (IPMDH1) works in methionine chain elongation, while IPMDH2 and IPMDH3 are involved in leucine biosynthesis (He et al., 2009 2011a; Sawada et al., 2009). Compared with the other steps, genes encoding branched-chain aminotransferases (BCATs) are relatively complicated due to the existence of six functional BCATs in the Arabidopsis genome. BCAT1 and BCAT2 are involved in the catabolism of branched-chain amino acids (Angelovici et al., 2013); BCAT3 has dual functions in both pathways (Knill et al., 2008); BCAT4 is exclusively involved in methionine chain elongation (Schuster et al., 2006); while the functions of BCAT5 and BCAT6 are still unclear (Angelovici et al., 2013). Taken together, a close relationship between the two pathways suggests that they are derived from a common ancestral pathway; or, more probably, the methionine chain-elongation pathway is evolutionarily recruited from leucine biosynthesis.


Distinct patterns of the histone marks associated with recruitment of the methionine chain-elongation pathway from leucine biosynthesis.

Xue M, Long J, Jiang Q, Wang M, Chen S, Pang Q, He Y - J. Exp. Bot. (2014)

Metabolic parallels between methionine chain elongation in aliphatic GLS (left) and the late steps of leucine biosynthesis (right). The dotted line indicates the repeated cycles to generate up to six methylene resdues. The genes specified in the methionine chain-elongation pathway are highlighted in red. In comparison, the genes functional in leucine biosynthetic pathway are highlighted in blue. The representative studies referring to the characterization of those genes are shown.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4321544&req=5

Figure 1: Metabolic parallels between methionine chain elongation in aliphatic GLS (left) and the late steps of leucine biosynthesis (right). The dotted line indicates the repeated cycles to generate up to six methylene resdues. The genes specified in the methionine chain-elongation pathway are highlighted in red. In comparison, the genes functional in leucine biosynthetic pathway are highlighted in blue. The representative studies referring to the characterization of those genes are shown.
Mentions: The cycles of methionine chain elongation consist of four enzymatic steps, namely condensation, isomerization, oxidative decarboxylation, and deamination (Fig. 1). Interestingly, a similar cycle of 2-oxo acid-based chain-elongation reactions is also utilized in leucine biosynthesis. More importantly, genes participating in each step of the two pathways are evolutionary homologues (Fig. 1). At the condensation step, two methylthioalkylmalate synthases (MAM1 and MAM3) share ~60% amino acid identity with the two isopropylmalate synthases (IPMS1 and IPMS2) (Textor et al., 20042007; de Kraker et al., 2007). The isomerization step is catalysed by isopropylmalate isomerases (IPMIs), which exist as heterodimeric enzymes and each consists of a large subunit encoded by a single gene, named LeuC, and a small subunit encoded by one of three genes, named LeuD1, LeuD2, and LeuD3. LeuC has dual functions in both pathways, while the functions of different LeuD genes are diversified, with LeuD1 and LeuD2 functional in methionine chain elongation, whereas LeuD3 is functional in leucine biosynthesis (Knill et al., 2009; Sawada et al., 2009; He et al., 2010; Imhof et al., 2014). Similarly, in the oxidative decarboxylation step, isopropylmalate decarboxylase 1 (IPMDH1) works in methionine chain elongation, while IPMDH2 and IPMDH3 are involved in leucine biosynthesis (He et al., 2009 2011a; Sawada et al., 2009). Compared with the other steps, genes encoding branched-chain aminotransferases (BCATs) are relatively complicated due to the existence of six functional BCATs in the Arabidopsis genome. BCAT1 and BCAT2 are involved in the catabolism of branched-chain amino acids (Angelovici et al., 2013); BCAT3 has dual functions in both pathways (Knill et al., 2008); BCAT4 is exclusively involved in methionine chain elongation (Schuster et al., 2006); while the functions of BCAT5 and BCAT6 are still unclear (Angelovici et al., 2013). Taken together, a close relationship between the two pathways suggests that they are derived from a common ancestral pathway; or, more probably, the methionine chain-elongation pathway is evolutionarily recruited from leucine biosynthesis.

Bottom Line: In general, genes involved in leucine biosynthesis were robustly associated with H3k4me2 and H3K4me3.This H3K4m3-depleted pattern had no effect on gene transcription, whereas it seemingly co-evolved with the entire pathway of aliphatic GLS biosynthesis.The results reveal a novel association of the epigenetic marks with plant secondary metabolism, and may help to understand the recruitment of the methionine chain-elongation pathway from leucine biosynthesis.

View Article: PubMed Central - PubMed

Affiliation: National Maize Improvement Center of China, Beijing Key Laboratory of Crop Genetic Improvement, China Agricultural University, Beijing 100193, China.

No MeSH data available.