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First published online September 3, 2009; doi:10.3732/ajb.0900059 American Journal of Botany 96: 1798-1807 (2009) © 2009 Botanical Society of America, Inc.

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A cellular study of teosinte Zea mays subsp. parviglumis (Poaceae) caryopsis development showing several processes conserved in maize¹

Marina Dermastia^2,3,5, Ale Kladnik³, Jasna Dolenc Koce³ and Prem S. Chourey⁴

² National Institute of Biology, Vecna pot 111, 1000 Ljubljana, Slovenia ³ Department of Biology, Biotechnical Faculty, University of Ljubljana, Vecna pot 111, 1000 Ljubljana, Slovenia ⁴ U. S. Department of Agriculture–Agricultural Research Service, Gainesville, Florida 32608 USA, and University of Florida, Gainesville, Florida 32611-0680 USA

ABSTRACT

The evolutionary history of maize (Zea mays subsp. mays) is of general interest because of its economic and scientific importance. Here we show that many cellular traits described previously in developing caryopses of maize are also seen in its wild progenitor teosinte (Zea mays subsp. parviglumis). These features, each with a possible role in development, include (1) an early programmed cell death in the maternal placento-chalazal (P-C) layer that may lead to increased hydrolytic conductance to the developing seed; (2) accumulation of phenolics and flavonoids in the P-C layer that may be related to antimicrobial activity; (3) formation of wall ingrowths in the basal endosperm transfer layer (BETL); (4) localization of cell wall invertase in the BETL, which is attributed to the increased transport capacity of photosynthates to the sink; and (5) endoreduplication in endosperm nuclei suggested to contribute to increased gene expression and greater sink capacity of the developing seed. In maize caryopsis, these cellular traits have been previously attributed to domestication and selection for larger seed size and vigor. Given the conservation of the entire cellular program in developing teosinte caryopses described here, we suggest that these traits evolved independently of domestication and predate human selection pressure.

Key Words: cell wall invertase • endoreduplication • genome size • maize • Poaceae • programmed cell death • teosinte • Zea mays subsp. parviglumis

Received for publication 20 February 2009. Accepted for publication 16 June 2009.

FOOTNOTES

¹ The authors thank D. Francis for critical reading of the manuscript, and Q.-B. Li and R. Hennen for technical assistance. This work was supported by the Slovenian Research Agency (grant No. P1-0212) and by U.S.A.-Slovenia Cooperation in Science and Technology (grant no. BI-US/06-07-031). This work was a cooperative investigation of the U. S. Department of Agriculture–Agricultural Research Service and the Institute of Food and Agricultural Science, University of Florida.

⁵ Author for correspondence (e-mail: marina.dermastia{at}nib.si)

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