Expressed sequence tag analysis in Cycas, the most primitive living seed plant

Eric D Brenner¹ , Dennis W Stevenson¹, Richard W McCombie², Manpreet S Katari², Stephen A Rudd³, Klaus FX Mayer³, Peter M Palenchar⁴, Suzan J Runko¹, Richard W Twigg¹, Guangwei Dai⁵, Rob A Martienssen⁶, Phillip N Benfey⁷ and Gloria M Coruzzi⁴

¹The New York Botanical Garden, 200th Street and Kazimiroff, Bronx, NY 10458-5126, USA

²Genome Research Center, Cold Spring Harbor Laboratory, 500 Sunnyside Blvd, Woodbury, NY 11797, USA

³Institut für Bioinformatik (IBI), GSF National Research Center for Environment and Health, Ingolstädter Landstrasse 1, 85764 Neuherberg, Germany

⁴New York University, Department of Biology 1009 Main Building, New York, NY 10003, USA

⁵Department of Computer Science, Courant Institute of Mathematical Sciences, New York University, 251 Mercer Street, New York, NY 10012-1185

⁶Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA

⁷Biology Department, Duke University, Box 91000, Durham, NC 27708, USA

author email corresponding author email

Genome Biology 2003, 4:R78doi:10.1186/gb-2003-4-12-r78


Published:	18 November 2003

Subject areas: Plant biology, Genome studies, Evolution

Abstract

Background

Cycads are ancient seed plants (living fossils) with origins in the Paleozoic. Cycads are sometimes considered a 'missing link' as they exhibit characteristics intermediate between vascular non-seed plants and the more derived seed plants. Cycads have also been implicated as the source of 'Guam's dementia', possibly due to the production of S(+)-beta-methyl-alpha, beta-diaminopropionic acid (BMAA), which is an agonist of animal glutamate receptors.

Results

A total of 4,200 expressed sequence tags (ESTs) were created from Cycas rumphii and clustered into 2,458 contigs, of which 1,764 had low-stringency BLAST similarity to other plant genes. Among those cycad contigs with similarity to plant genes, 1,718 cycad 'hits' are to angiosperms, 1,310 match genes in gymnosperms and 734 match lower (non-seed) plants. Forty-six contigs were found that matched only genes in lower plants and gymnosperms. Upon obtaining the complete sequence from the clones of 37/46 contigs, 14 still matched only gymnosperms. Among those cycad contigs common to higher plants, ESTs were discovered that correspond to those involved in development and signaling in present-day flowering plants. We purified a cycad EST for a glutamate receptor (GLR)-like gene, as well as ESTs potentially involved in the synthesis of the GLR agonist BMAA.

Conclusions

Analysis of cycad ESTs has uncovered conserved and potentially novel genes. Furthermore, the presence of a glutamate receptor agonist, as well as a glutamate receptor-like gene in cycads, supports the hypothesis that such neuroactive plant products are not merely herbivore deterrents but may also serve a role in plant signaling.