Paper of the month
 

Paper of the month (March 2011)

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Occurrence of unique three-celled megagametophyte and single fertilization in an aquatic angiosperm-Dalzellia zeylanica (Podostemaceae-Tristichoideae)

 

Anita Sehgal1, Jitendra P. Khurana2, Minakshi Sethi1 and Hussain Ara3
(1) Department of Botany, Miranda House, University of Delhi, Delhi, 110007, India
(2) Interdisciplinary Centre for Plant Genomics and Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi, 110021, India
(3) National Institute of Plant Genome Research (NIPGR), Aruna Asaf Ali Marg, New Delhi, 110067, India

 

Reference: Sehgal et al (2011) Sexual Plant Reproduction, (doi:10.1007/s00497-010-0159-3)

 

Summary

Angiosperms are characterized by the occurrence of double fertilization. However, Podostemaceae is considered an exception with the presence of only single fertilization (syngamy) though two male gametes are formed conventionally. To determine the cause for the failure of double fertilization in Dalzellia zeylanica (Gardn.) Wight, we closely tracked the movement of the male gametes from the time of pollen tube initiation to the time of entry into the megagametophyte to affect fertilization. We report for the first time, the presence of a novel type of three-nucleate/three-celled mature megagametophyte consisting of two synergids and an egg cell in D. zeylanica. Therefore, of the two male gametes formed in this plant, one fuses with the egg cell resulting in syngamy, whereas the other male gamete eventually degenerates due to the absence of its partner i.e. single polar nucleus of the central cell that degenerates prior to the entry of the pollen tube into the synergid. The present work not only highlights the highly reduced nature of megagametophyte but also the occurrence of single fertilization resulting in sperm selection in D. zeylanica.


Electronic supplementary material The online version of this article (doi:10.1007/s00497-010-0159-3) contains supplementary material, which is available to authorized users.

Keywords Aquatic angiosperm – Male gametes – Megagametogenesis – Pollination – Single fertilization – Three-celled megagametophyte

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