Academic journal article Genetics

A Collection of Ds Insertional Mutants Associated with Defects in Male Gametophyte Development and Function in Arabidopsis Thaliana

Academic journal article Genetics

A Collection of Ds Insertional Mutants Associated with Defects in Male Gametophyte Development and Function in Arabidopsis Thaliana

Article excerpt

ABSTRACT

Functional analyses of the Arabidopsis genome require analysis of the gametophytic generation, since ~10% of the genes are expressed in the male gametophyte and ~9% in the female gametophyte. Here we describe the genetic and molecular characterization of 67 Ds insertion lines that show reduced transmission through the male gametophyte. About half of these mutations are male gametophytic-specific mutations, while the others also affect female transmission. Genomic sequences flanking both sides of the Ds element were recovered for 39 lines; for 16 the Ds elements were inserted in or close to coding regions, while 7 were located in intergenic/unannotated regions of the genome. For the remaining 16 lines, chromosomal rearrangements such as translocations or deletions, ranging between 30 and 500 kb, were associated with the transposition event. The mutants were classified into five groups according to the developmental processes affected; these ranged from defects in early stages of gametogenesis to later defects affecting pollen germination, pollen tube growth, polarity or guidance, or pollen tube-embryo sac interactions or fertilization. The isolated mutants carry Ds insertions in genes with diverse biological functions and potentially specify new functions for several unannotated or unknown proteins.

PLANTS alternate growth of the diploid sporophyte with a highly reduced haploid gametophyte. Specialized cells within sporophytic structures of the flower undergo meiosis and subsequent mitoses to form the male (pollen) and female (embryo sac) gametophytes. Upon maturation, the embryo sac consists of seven cells, classified into four cell types with specialized functions (Drews and Yadegari 2002; Dresselhaus 2006). The mature malegametophyte (pollen grain),composed of a generative cell (or two sperm cells) and a vegetative cell, is an autonomous organism. Upon hydration on the stigma the vegetative cell produces a tip-growing extension, the pollen tube, which transports and discharges the sperm cells into the embryo sac, where double fertilization occurs (Boavida et al. 2005).

Gametogenesis depends on coordination of sporophytic and gametophytic gene expression (McCormick 2004; Yadegari and Drews 2004). Expression profiles of female (Yu et al. 2005; Steffen et al. 2007) and male gametophytes (Becker et al. 2003; Honys and Twell 2003, 2004; Pina et al. 2005) have provided lists of genes that may be under gametophytic selection. Microscopicbased screens for semisterility or for alterations in pollen morphology or cell division patterns have been used to identify genes required inthe male(ChenandMcCormick 1996; Park et al. 1998; Johnson and McCormick 2001; Lalanne and Twell 2002) or female (Christensen et al. 1998; Shimizu andOkada 2000; Siddiqi et al. 2000; Huck et al. 2003) gametophytes. Functional analysis of gametophytic-expressed genes is still incomplete, especially for genes required for pollen tube growth or for interaction with female tissues. Since gametophytic mutations affect haploid-expressed functions, they are not transmitted through the defective gamete and can be recovered only in a heterozygous state. Therefore, genetic screens for these traits are challenging to perform, unless a pollen reporter marker is used ( Johnson et al. 2004). For this reason, transposon and T-DNA insertional mutagenesis emerged as an attractive alternative, since identification of gametophytic mutants is based on altered segregation ratios of a linked antibiotic resistance marker (Feldmann et al. 1997; Bonhomme et al. 1998; Howden et al. 1998; Johnson et al. 2004; Lalanne et al. 2004; Pagnussat et al. 2005).

Here we describe the genetic andmolecular characterization of a collection of Ds insertion lines (Sundaresan et al. 1995) that show transmission defects through the male gametophyte.Agenetic screen performed with this collection by Pagnussat et al. (2005) led to the identification of 130 mutants affected in female gametophyte development and function. …

Search by... Author
Show... All Results Primary Sources Peer-reviewed

Oops!

An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.