Abstract Detail

Development and Structure

Hu, Mingli [1], Ren, Zhanhong [2], Rong, Ning [3], Bai, Mei [3], Wu, Hong [3], Yang, Ming [4].

A possible pattern in the evolution of male meiotic cytokinesis in angiosperms.

Evolution of cellular characteristics is a fundamental aspect of evolutionary biology, but knowledge about evolution at the cellular level is very limited. In particular, whether there are certain cellular characteristics occurring exclusively in basal angiosperms and closely related species and evolving into other forms in other angiosperm lineages remains an unanswered question. We recently reported that bidirectional cytokinesis occurs in male meiosis in Nymphaea colorata and Magnolia denudata with concurrent centripetal and centrifugal wall growth from the cell periphery and a cell wall island (CWI) in the cell center, respectively. This type of cytokinesis is characterized by discontinuous cell plates or walls in their side views that have not been described in other angiosperm species. N. colorata is a basal angiosperm species and M. denudata belongs to an ancient lineage that is phylogenetically close to basal angiosperms. To further investigate whether bidirectional cytokinesis occurs in a relatively young lineage in Magnoliales, we examined male meiotic cytokinesis in Mitrephora thorelii Pierre in Annonaceae. The current phylogeny of Magnoliales places Magnoliaceae at a more basal position than Annonaceae. After examining more than 50 microsporocytes at the cytokinesis stage, we did not find a CWI in a microsporocyte in M. thorelii. Therefore, male meiotic cytokinesis in M. thorelii appeared to be centripetally unidirectional. Based on the published images, male meiotic cytokinesis in Pseuduvaria trimera, another species in Annonaceae, is also likely centripetally unidirectional. Having the same kind of unidirectional cytokinesis in M. thorelii and P. trimera should not be surprising as they are in the genera belonging to the short-branch clade of Annonaceae with similarly recent evolutionary divergence times. For comparisons with the hitherto described species, male meiotic cytokinesis is known to be centrifugally unidirectional in monocot species and centripetally unidirectional in eudicot species. Taken together, these observations are consistent with the hypothesis that male meiotic cytokinesis was bidirectional in basal angiosperms and other ancient lineages such as Magnolia, and it became either centripetally or centrifugally unidirectional during angiosperm evolution. This hypothesis can and should be tested in additional species such as those in the ANITA grade. It is noted that the bidirectional cytokinesis discussed here refers to the bidirectional cell plate or wall formation during cytokinesis, not bidirectional cell wall thickening (callose deposition) post cytokinesis (after the cell plate or initial wall has been formed) that has been found in microsporogenesis in eudicot species.

1 - Hubei University of Science and Technology, School of Pharmacy, Xianning Medical College, Xianning, Hubei, 437100, China
2 - Hubei University of Science and Technology, Hubei Key Laboratory of Diabetes and Angiopathy, Medicine Research Institute, Xianning Medical College, Xianning, Hubei, 437100, China
3 - South China Agricultural University, State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Sciences, Guangzhou, Guangdong, 510642, China
4 - Oklahoma State University, 301 Physical Sciences, Department Of Plant Biology, Ecology, And Evolutio, Stillwater, OK, 74078, United States

Keywords:
microsporogenesis
centripetal and centrifugal cytokinesis
cell morphology
angiosperm lineages.

Presentation Type: Oral Paper
Number: DS5006
Abstract ID:334
Candidate for Awards:None