Abstract Detail

Cell biology

Yan, Xiaodong [1], Bai, Mei [1], Ning, Xiping [1], Ouyang, Haibo [2], Zhang, Shouzhou [3], Yang, Ming [4], Wu, Hong [1].

Spatiotemporal features of microsporogenesis in the cycad species Macrozamia communis L. A. S. Johnson (Zamiaceae).

Advance local cell wall ingrowths at future cytokinetic sites are characteristic of sporogenesis in non-seed land plants and of microsporogenesis in basal angiosperms such as magnoliids. Sparse evidence suggests that such a feature also occurs in microsporogenesis in basal gymnosperms such as cycads. Further detailed investigation into microsporogenesis in a cycad may shed light on the evolutionary relationship between gymnosperms and angiosperms. To this end, we used bright-field and epifluorescence microscopy, confocal laser scanning microscopy, and transmission electron microscopy to investigate the microsporogenic process in Macrozamia communis, a species in the Zamiaceae family of cycads. In prophase-II microsporocytes in M. communis, a local cell wall ingrowth in the form of a callose ring occurs between the newly formed nuclei, and it is not accompanied by cytokinetic apparatuses such as mini-phragmoplasts, wide tubules, and wide tubular networks. Shortly after the second nuclear division, a second callose ring also forms between the newly formed nuclei. Subsequent cell plate formation in the planes of the callose rings results in tetragonal tetrads. The advance formation of callose rings in microsporogenesis in M. communis is similar to that in magnoliids, both of which appear to be more closely related to the cytokinetic mode in sporogenesis in non-seed land plants than those in other gymnosperms and angiosperms. Based on these observations, we propose that advance formation of cell wall ingrowths at future cytokinetic sites is an ancestral feature, in addition to the previously proposed ancestral feature of simultaneous cytokinesis in microsporogenesis in angiosperms. The similarities in microsporogenesis between cycads and magnoliids support the hypothesis that extant gymnosperms and angiosperms have a common origin and have undergone independent evolution as suggested by molecular phylogenetic studies.

1 - South China Agricultural University, State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangzhou, Guangdong, 510642, China
2 - Fujian Institute of Subtropical Botany, Xiamen, Fujian, 361006, China
3 - Shenzhen Fairylake Botanical Garden, Shenzhen, Guangdong, 518004, China
4 - Oklahoma State University, 301 Physical Science, Stillwater, OK, 74078, USA

Keywords:
angiosperm
callose
cycads
cytokinesis
Evolution
gymnosperm
magnoliids
microsporogenesis.

Presentation Type: Oral Paper:Papers for Topics
Session: 58
Location: Salon 17/The Shaw Conference Centre
Date: Wednesday, July 29th, 2015
Time: 9:15 AM
Number: 58006
Abstract ID:368
Candidate for Awards:None