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RESEARCH ARTICLE
Contents Vol 33(9)

Steryl glucoside concentration declines with Cycas micronesica seed age

Thomas E. Marler A C , Vivian Lee B , J. Chung B and Christopher A. Shaw B
+ Author Affiliations
- Author Affiliations

A CNAS-AES, University of Guam, UOG Station, Mangilao, GU 96923, USA.

B Department of Ophthalmology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.

C Corresponding author. Email: tmarler@uog.edu

Functional Plant Biology 33(9) 857-862 https://doi.org/10.1071/FP05321
Submitted: 23 December 2005  Accepted: 22 May 2006   Published: 1 September 2006

Abstract

Neurotoxins contained in the seeds of Cycas micronesica K.D. Hill have been implicated in the Guam neurological disease cluster, amyotrophic lateral sclerosis–parkinsonism dementia complex (ALS–PDC). Some of these neurotoxins remain in the washed cycad seed flour that was historically an important part of the Chamorro diet. Of these, variant steryl glucosides have been identified by us as a possible etiological factor in the disease. In vitro and in vivo animal studies have strongly supported a role for these molecules in some forms of neurodegeneration. As part of a series of studies, we have now determined the concentrations of several steryl glucosides and their sterol precursors as affected by the age of C. micronesica seeds. The concentration of these molecules declined with seed age from 2.0 to 30.5 months. Following log-transformation of both axes, the decline was linear. Similarly, concentration of all but one of the molecules declined with age when samples were restricted to gametophyte tissue. Factors suspected of influencing phenotypic plasticity must be addressed when interpreting plant physiology data. Our results confirm for the first time that tissue age must be documented and reported in cycad seed biochemistry studies to remove ambiguities from results. Past studies in this important area of research have failed to account for the potential impact of seed age, rendering previous outcomes and interpretations of cycad neurotoxins in their impact on ALS–PDC ambiguous.

Keywords: ALS–PDC, cycad, Cycas micronesica, neurotoxin, seed age, sterol, steryl glucoside.


Acknowledgments

We thank N Dongol for field assistance. Support provided by USDA CSREES Tropical and Subtropical Agricultural Research Grants Program (Project 2003-05495) to TEM and USA Army Medical and Materiel Command (DAMD17-02-1-0678), NSERC Canada, and Scottish Rite Charitable Foundation of Canada to CAS.


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