Abstract
Many homeotic MADS-box genes have been identified as controllers of the floral transition and floral development. However, information regarding Bsister (Bs)-function genes in monocots is still limited. Here, we describe the functional characterization of a Bs-group MADS-box gene FEMALE-STERILE (FST), whose frame-shift mutation (fst) results in abnormal ovules and the complete abortion of zygotic embryos and endosperms in rice. Anatomical analysis showed that the defective development in the fst mutant exclusively occurred in sporophytic tissues including integuments, fertilized proembryos and endosperms. Analyses of the spatio-temporal expression pattern revealed that the prominent FST gene products accumulated in the inner integument, nucellar cell of the micropylar side, apical and base of the proembryos and free endosperm nuclei. Microarray and gene ontology analysis unraveled substantial changes in the expression level of many genes in the fst mutant ovules and seeds, with a subset of genes involved in several developmental and hormonal pathways appearing to be down-regulated. Using both forward and reverse genetics approaches, we demonstrated that rice FST plays indispensable roles and multiple functions during ovule and early seed development. These findings support a novel function for the Bs-group MADS-box genes in plants.
Highlights
Sexual reproduction in higher plants includes a key phase to produce male and female gametes, ensuring pollination and fertilization
Important key developmental biology questions that remain unanswered include: how is the pattern of formation accomplished, and how does the genetic interaction of floral homeotic genes occurs at the molecular level? extensive knowledge on these MADS domain transcription factors that regulate the floral transition and floral organ development is available, little is known regarding the molecular mechanisms they employ to act as the developmental switches for specifying the female reproductive unit in flowering plants
The fst Mutation Leads to Sporophytic Female Sterility The spontaneous fst mutant plants exhibited similar morphology to that of the wild-type (WT) plants but are completely female sterile
Summary
Sexual reproduction in higher plants includes a key phase to produce male and female gametes, ensuring pollination and fertilization. Extensive knowledge on these MADS domain transcription factors that regulate the floral transition and floral organ development is available, little is known regarding the molecular mechanisms they employ to act as the developmental switches for specifying the female reproductive unit in flowering plants. It is unclear how the homeotic transcription factors organize the spatial patterns of cell differentiation during diverse or specific developmental processes such as embryonic shoot/root initiation and endosperm formation in a developing seed
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