ABSTRACT
In most sexually reproducing plants, a single somatic, sub-epidermal cell in an ovule is selected to differentiate into a megaspore mother cell, which is committed to giving rise to the female germline. However, it remains unclear how intercellular signaling among somatic cells results in only one cell in the sub-epidermal layer differentiating into the megaspore mother cell. Here we uncovered a role of the THO complex in restricting the megaspore mother cell fate to a single cell. Mutations in TEX1, HPR1, and THO6, components of the THO/TREX complex, led to the formation of multiple megaspore mother cells, which were able to initiate gametogenesis. We demonstrated that TEX1 repressed the megaspore mother cell fate by promoting the biogenesis of TAS3-derived trans-acting small interfering RNA (ta-siRNA), which represses ARF3 expression. The TEX1 protein was present in epidermal cells, but not in the germline, and, through TAS3-derived ta-siRNA, restricted ARF3 expression to the medio domain of ovule primordia. Expansion of ARF3 expression into lateral epidermal cells in a TAS3 ta-siRNA-insensitive mutant led to the formation of supernumerary megaspore mother cells, suggesting that TEX1- and TAS3-mediated restriction of ARF3 expression limits excessive megaspore mother cell formation non-cell-autonomously. Our findings reveal the role of a small-RNA pathway in the regulation of female germline specification in Arabidopsis.
Subject(s)
Gametogenesis, Plant/physiology , Gene Expression Regulation, Plant/physiology , Ovule/physiology , RNA, Small Interfering/genetics , Signal Transduction/genetics , Arabidopsis , Arabidopsis Proteins/genetics , Arabidopsis Proteins/metabolism , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Mutation , Nuclear Proteins/genetics , Nuclear Proteins/metabolism , RNA, Small Interfering/metabolism , RNA-Dependent RNA Polymerase/genetics , RNA-Dependent RNA Polymerase/metabolismABSTRACT
UNLABELLED: The National Agricultural Biotechnology Information Center (NABIC) constructed a web-based database to provide information about 54,310 single nucleotide polymorphisms (SNPs) identified in the seven species in a high-throughput manner. The database consists of three major functional categories: SNP marker search, detailed information viewer and download of SNP sequence. The SNP annotation table provides detailed information such as ownership information, basic information, bio-entry information, reference, comments, features, and sequence data. AVAILABILITY: The database is available online for free at http://nabic.rda.go.kr/SNP.
