A Cactus by Any Other Name

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Science  27 Jan 2012:
Vol. 335, Issue 6067, pp. 382
DOI: 10.1126/science.335.6067.382-c
CREDIT: CHEN ET AL., PROC. NATL. ACAD. SCI. U.S.A. 109, 10.1073/PNAS.1120992109 (2012)

Lignin polymers toughen up plant cell walls, which may be good for the plant that needs to stand up tall but is inconvenient for industrial processes such as those that generate pulp or biofuels. Most lignins are assembled from a small handful of common monomer types. Chen et al. have now identified a lignin that is constructed from an unusual subunit, the catechyl (C) monolignol caffeyl alcohol. The lignins in the black coats of seeds within the vanilla bean are entirely composed of these catechyl subunits. Other portions of the vanilla plant—the seed pod, stem, and leaves—instead contain the more standard sort of lignin, without the C subunit. A similarly high content of C-lignin was also found in seed coats of several cactus species, seeds that, like the vanilla seeds, carried black coats. Thus, there is greater natural diversity in these sturdy polymers than previously appreciated.

Proc. Natl. Acad. Sci. U.S.A. 109, 10.1073/pnas.1120992109 (2012).

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