The dyad gene is required for progression through female meiosis in Arabidopsis

Abstract

In higher plants the gametophyte consists of a gamete in association with a small number of haploid cells, specialized for sexual reproduction. The female gametophyte or embryo sac, is contained within the ovule and develops from a single cell, the megaspore which is formed by meiosis of the megaspore mother cell. The dyad mutant of Arabidopsis, described herein, represents a novel class among female sterile mutants in plants. dyad ovules contain two large cells in place of an embryo sac. The two cells represent the products of a single division of the megaspore mother cell followed by an arrest in further development of the megaspore. We addressed the question of whether the division of the megaspore mother cell in the mutant was meiotic or mitotic by examining the expression of two markers that are normally expressed in the megaspore mother cell during meiosis. Our observations indicate that in dyad, the megaspore mother cell enters but fails to complete meiosis, arresting at the end of meiosis 1 in the majority of ovules. This was corroborated by a direct observation of chromosome segregation during division of the megaspore mother cell, showing that the division is a reductional and not an equational one. In a minority of dyad ovules, the megaspore mother cell does not divide. Pollen development and male fertility in the mutant is normal, as is the rest of the ovule that surrounds the female gametophyte. The embryo sac is also shown to have an influence on the nucellus in wild type. The dyad mutation therefore specifically affects a function that is required in the female germ cell precursor for meiosis. The identification and analysis of mutants specifically affecting female meiosis is an initial step in understanding the molecular mechanisms underlying early events in the pathway of female reproductive development.

Low Female Gametophyte Fertility Contributes to the Low Seed Formation of the Diploid Loquat [Eriobotrya Japonica (Thunb.) Lindl.] Line H30-6

“…The formation of both male and female gametophytes is a precisely coordinated process, including the formation of gametophyte mother cells, meiosis, and gametophyte development. Therefore, there are three likely mechanisms leading to low gametophyte fertility: pre meiosis abnormality, such as a lack of sporogenous cells (Schiefthaler et al, 1999 ; Yang et al, 1999 ) and defects in meiotic entry (Hong et al, 2012 ), meiosis abnormalities, such as arrests at one meiosis period (Siddiqi et al, 2000 ) and aberrant chromosome distribution (Hoyt and Geiser, 1996 ; d'Erfurth et al, 2008 ; De Storme and Geelen, 2011 ), and postmeiotic abnormality, especially reproductive companion cell abnormalities, which will cause gametophytes to be sterile (Chaubal et al, 2000 ; Guo et al, 2001 ; Suzuki et al, 2001 ; Smith et al, 2002 ; Kawanabe et al, 2006 ; Li et al, 2006 ; Zhang et al, 2006 ). In this study, we found no premeiotic or post-meiotic abnormalities but a multitude of meiosis abnormal phenomena of PMCs.…”

Transcriptomic analyses in the gametophyte of Dryopteris affinis: apomixis and more

“…A deeper study of how these transcription factors influence the genome of the D. affinis gametophyte would allow a better understanding of the mechanisms behind apomixis. Finally, other proteins with a possible role in asexual reproduction are SWITCH1 (SWI1), required in A. thaliana during meiosis of male and female gametes, and chromatin remodelling (Siddiqi et al, 2000); and BRI1-ASSOCIATED RECEPTOR KINASE (BAK1), intervening in somatic embryogenesis and embryo sac development in Poa pratensis (Albertini et al, 2005).…”