Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2009
Publication Date: 9/3/2009
Citation: Dermastia, M., Kladnik, A., Koce, J.D., Chourey, P.S. 2009. A cellular study of teosinte Zea mays ssp. parviglumis (Poaceae) caryopsis development showing several processes conserved in maize. American Journal of Botany. 96(10): 1798-1807.
Interpretive Summary: Today’s maize seed and plant is a product of intense selction and breeding efforts of more than a centuary. A previous cellular level collaborative study between scientists from University of Ljubljana, Slovenia and Chemistry Unit, CMAVE, ARS, Gainesville, FL, led to several unexpected discoveries in terms of cellular structures and function in developing seed of maize. We hypothesized then that these entities may have originated during the domestication and man-made selection for increased seed size, and resistance to pathogen and drought. To test this hypothesis, the same group has now examined developing seeds of teosinte, an ancestral grass which gave rise to maize nearly 10,000 rears ago. To our surprise, we found no qualitative difference for these cellular traits between maize and teosinte even though the two are highly divergent in seed and plant architecture. Clearly, these cellular traits were embedded in the teosinte seed through natural selection independent of human selection and domestication.
Technical Abstract: Although recent molecular studies elucidate the genetic background leading to changed morphology of maize female inflorescence and the structure of the caryopsis during the domestication of maize (Zea mays ssp. mays) from its wild progenitor teosinte (Zea mays ssp. parviglumis), the mechanisms underlying the caryopsis development of teosinte have not been investigated yet. This study shows that many previously described cellular traits in developing caryopses of maize and attributed to various functions potentially associated with human selection for larger seed size are also seen in teosinte. Notably, early programmed cell death in the maternal placento-chalazal (P-C) layer may lead to increased hydrolytic conductance to the developing seed. Accumulation of phenolic acids and flavonoids in the integumental P-C layer may be related to antimicrobial activity possibly preventing transmission of pathogens to the next generation. Cell wall-in-growth formation in the basal endosperm transfer layer (BETL) and the localization of cell wall invertase transcripts in the BETL may increase transport capacity of photosynthates. Similarly, endoreduplication in both endosperm and pericarp nuclei may contribute to increased gene expression and greater sink capacity of the developing teosinte seed. Collectively, these results indicate that the essential caryopsis developmental cellular processes are conserved in teosinte and maize.