34:	Detection of nuclear DNA degradation during sexual determination in corn.

Authors:	Nungaray, Anthony(A)Carroll, Tanya(A)Calderon-Urrea, Alejandro(A)
Affiliations:	(A): California State University, Fresno
Presenter:	Nungaray, Anthony , calalea@csufresno.edu

Apoptosis is a type of programmed cell death (PCD) in animals, which results in the death of a cell. One of the hallmarks of apoptosis is the organized degradation of the nuclear DNA. Apoptosis has been studied with the TUNEL assay, which labels 3’-OH ends produced as a result of DNA degradation. PCD is also important during plant development. In corn, sex determination is accomplished through the regular degeneration of organ primordia of the opposite sex within the appropriate structures--tassel (male flowers) or ear (female flowers). It has been suggested that nuclear DNA degradation is involved in this degenerative process. Our studies have focused on the detection of DNA degradation during the programmed cell death that occurs in male flower formation. Using two in situ staining techniques, acridine orange fluorescence and the TUNEL assay, we studied the development of immature tassels from wild type and tasselseed2 mutant plants. The acridine orange fluorescent staining technique allowed us to detect the absence of nuclear DNA in degenerating wild type gynoecium primordia. We were able to show, by using the TUNEL assay, that this loss of nuclear DNA is due to a highly controlled DNA degradation process. Conversely, in tasselseed2 mutant plants, no nuclear loss is observed in developing gynoecium while stamens showed staining with the TUNEL assay. Our results further support the idea that gynoecium degeneration during male flower formation and subsequent programmed organ death is a result of the action of the TASSELSEED2 gene and that it involves DNA degradation. Whether or not this was an apoptotic event has yet to be determined.