RASPBERRY3Gene Encodes a Novel Protein Important for Embryo Development

Abstract

We identified a new gene that is interrupted by T-DNA in an Arabidopsis embryo mutant called raspberry3. raspberry3 has "raspberry-like" cellular protuberances with an enlarged suspensor characteristic of other raspberry embryo mutants, and is arrested morphologically at the globular stage of embryo development. The predicted RASPBERRY3 protein has domains found in proteins present in prokaryotes and algae chloroplasts. Computer prediction analysis suggests that the RASPBERRY3 protein may be localized in the chloroplast. Complementation analysis supports the possibility that the RASPBERRY3 protein may be involved in chloroplast development. Our experiments demonstrate the important role of the chloroplast, directly or indirectly, in embryo morphogenesis and development.The molecular and cellular mechanisms that program the series of events leading to the development of a plant embryo are not well understood. Embryogenesis is a complex process that requires regulation of cell-specific and housekeeping genes within the embryo proper and neighboring seed tissues (e.g. endosperm) surrounding the embryo (Goldberg et al., 1994). In Arabidopsis, it has been estimated from genetic studies that there are about 4,000 essential genes and about 40 embryonic patterning genes that are required for normal plant embryogenesis (Jü rgens et al., 1991). The regulation of these genes must be tightly coordinated and controlled in a spatially and timely manner starting from the zygote to the mature embryo in dormant seeds (Goldberg et al., 1989; West and Harada, 1993;Jü rgens, 1995;Jü rgens et al., 1995). How the plant embryo achieves this coordination is not yet known and is a major question of plant developmental biology.A genetic approach is one of the strategies adopted to begin to understand the process of plant embryogenesis. There are more than 2,000 Arabidopsis embryo mutants that have been isolated by several laboratories over the last 10 years using ethyl methanesulfonate mutagenesis, T-DNA insertional inactivation, and transposon tagging (Errampalli et al., 1991;Mayer et al., 1991;Meinke et al., 1994;Schwartz et al., 1994;Yadegari et al., 1994; Altmann et al., 1995; Devic et al., 1996;McElver et al., 2001). The largest class of mutants within these collections are those that remain morphologically globular in shape (Errampalli et al., 1991;Mayer et al., 1991;Meinke et al., 1994;Schwartz et al., 1994;Yadegari et al., 1994). The raspberry (rsy) mutants, including rsy1 and rsy2, belong to this class (Yadegari et al., 1994).Several embryo mutants have been characterized, leading to the identification of embryo genes and what their functions are during embryo development. Some genes encode proteins that are involved in transcription or that are associated with transcription factors (Aida et al., 1997;Hardtke and Berleth, 1998;Li and Thomas, 1998;Lotan et al., 1998;Stone et al., 2001). Others encode proteins that are important for cell division, cell polarity, differentiation (Berleth and Jü rgens, 1993;Shevell et al., 1994;...

In silico identification and characterization of putative differentially expressed genes involved in common bean (Phaseolus vulgaris L.) seed development

“…Identical results were obtained in abnormal suspensor (sus) mutants (Schwartz et al 1994), and raspberry (rsy) mutants (Apuya et al 2002) of Arabidopsis thaliana.…”

Analysis of chlorophyll fluorescence reveals stage specific patterns of chloroplast-containing cells during Arabidopsis embryogenesis

“…Although it has been reported previously that chloroplasts are present in the late stages of Arabidopsis embryogenesis (Apuya et al, 2002;Apuya et al, 2001;GutierrezNava et al, 2004) and that chlorophyll fluorescence is widely used as a background marker in embryo imaging, to our knowledge a detailed description of the embryonic stages and cell types that contain chloroplasts have not been reported previously. In order to determine if stage specific patterns of chloroplast-containing cells are present during Arabidopsis embryogenesis, we have quantified chlorophyll fluorescence as a marker for plastids that have differentiated into chloroplasts.…”

“…Anterograde and retrograde signals between the nucleus and plastids have been demonstrated to participate in chloroplast biogenesis during early stages of embryogenesis (Woodson and Chory, 2008). Mutations in nuclear-encoded genes for chloroplast localized proteins are often embryonically lethal (Apuya et al, 2002;Hormann et al, 2004;Kubis et al, 2004;Lopez-Juez, 2007;Uwer et al, 1998;Xu and Moller, 2004;Yu et al, 2004). Additionally, TargetP predictions of 220 EMB genes, required for normal Arabidopsis embryo development, suggest that 32% of these genes are directed to chloroplasts (Tzafrir et al, 2004).…”

“…In the more severe cases, embryo development is arrested prior to the globular stage of embryogenesis. These embryonically lethal nuclear mutants, with altered chloroplast biogenesis, affect the early stages of chloroplast development prior to the accumulation of the photosynthetic genes and thylakoid formation (Apuya et al, 2002;Hormann et al, 2004;Kubis et al, 2004;Lopez-Juez, 2007;Uwer et al, 1998;Xu and Moller, 2004;Yu et al, 2004). This strongly suggest that chloroplast function is necessary for proper Arabidopsis embryogenesis (Lopez-Juez, 2007).…”

Development of the embryo proper and the suspensor during plant embryogenesis

“…RSY3 encodes a novel protein that is localized in chloroplasts, and it has been suggested that RSY3 protein is required for chloroplast differentiation and embryonic development (Apuya et al 2002). However, the direct factors produced by the embryo proper to suppress the embryogenic potential of suspensor cells have not been identified in this mutant.…”