Convergent Evolution of Syringyl Lignin Biosynthesis via Distinct Pathways in the Lycophyte Selaginella and Flowering Plants

Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907, USA.
The Plant Cell (Impact Factor: 9.34). 04/2010; 22(4):1033-45. DOI: 10.1105/tpc.109.073528
Source: PubMed


Phenotypic convergence in unrelated lineages arises when different organisms adapt similarly under comparable selective pressures. In an apparent example of this process, syringyl lignin, a fundamental building block of plant cell walls, occurs in two major plant lineages, lycophytes and angiosperms, which diverged from one another more than 400 million years ago. Here, we show that this convergence resulted from independent recruitment of lignin biosynthetic cytochrome P450-dependent monooxygenases that route cell wall monomers through related but distinct pathways in the two lineages. In contrast with angiosperms, in which syringyl lignin biosynthesis requires two phenylpropanoid meta-hydroxylases C3'H and F5H, the lycophyte Selaginella employs one phenylpropanoid dual meta-hydroxylase to bypass several steps of the canonical lignin biosynthetic pathway. Transgenic expression of the Selaginella hydroxylase in Arabidopsis thaliana dramatically reroutes its endogenous lignin biosynthetic pathway, yielding a novel lignin composition not previously identified in nature. Our findings demonstrate a unique case of convergent evolution via distinct biochemical strategies and suggest a new way to genetically reconstruct lignin biosynthesis in higher plants.

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    • " the highest being 88% in the ccr mutant ( Van Acker et al . , 2013 ) . The hydrolysis of Arabidopsis mutants shows that increases of cellulose saccharification by engineering monolignol biosynthesis can be the basis for monolignol pathway engineering in other species . Different species may have alternative routes for mono - lignol biosynthesis ( Weng et al . , 2010 ; Zhou et al . , 2010 ) , and down - regulation of specific monolignol pathway genes in different species may not have the same effects . For example , down - regulation of C3H in Arabidopsis caused reduction of both G and S monolignols ( Ralph et al . , 2006 ) . However , in a hybrid poplar ( Populus alba 9 grandidentata ) , the lignin"
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    Plant Biotechnology Journal 10/2014; 12(9). DOI:10.1111/pbi.12273 · 5.75 Impact Factor
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    • "The reaction was incubated for 20 min at 30 °C after adding the yeast microsomal extract, and was terminated by adding glacial acetic acid. The samples were extracted with ethyl acetate, vacuum dried and redissolved in 50 % methanol, and analyzed by HPLC (Weng et al. 2010a). To test the activity of EglF5H, different substrates and concentrations were employed. "
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    • "The chemical composition of gymnosperm xylem is characterized by a guaiacyl-rich (G type) lignin and the absence of syringyl (S type) subunits [81]. The lignins in the xylem of woody dicots, gnetales, and Selaginella (a lycopod) are characterized by a mixed polymer of S and G subunits (S/G lignin) [82]. The hemicelluloses of pines are a mixture of heteromannans, while dicot hemicelluloses are typically xylan-rich [83]. "
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