Abstract
The glycine-rich domain proteins (GRDP) have been functionally implicated in the cell wall structure, biotic, and abiotic stress responses. However, little is known about GRDP genes in female gametophyte development of Arabidopsis. This study shows that GRDP2, a GRDP, plays a crucial role in female gametophyte development. In GRDP2 overexpression lines, grdp2-3, the embryo sacs were arrested at FG1 and no nucleus stages. Furthermore, callose staining shows that cell plate formation during megasporogenesis is disturbed in grdp2-3. In contrast, the pollen development is not affected in grdp2-3. The expression patterns of auxin-specific marker lines in female gametophytes showed that the auxin distribution and transport were significantly changed during megagametogenesis in grdp2-3. In addition, compared with the membrane-localized pattern of PIN1, PIN2, and PIN7 in WT, the signals were detected in the cytoplasm in grdp2-3. Together, our data suggest that GRDP2 plays an essential role in auxin-mediated female gametophyte development.
Highlights
Proteins with particular glycine-rich regions have been reported in seed coat and cell wall of a wide variety of plants; for example, soybean seed coat contains 21% of glycine, the cell wall of milkweed stem has 31%, and coat coleoptile cells have 27% of glycine (de Oliveira et al, 1990)
We further showed that GRDP2 overexpression results in two types of ovule development defects in Arabidopsis thaliana, the abnormal arrest at one nucleus stage (FG1 stage) and the nucleus degeneration
Overexpression of GRDP2 Causes Reduced Plant Fertility In Arabidopsis, glycine-rich domain protein (GRDP) is encoded by a single copy gene GRDP2, and its genomic organization consists of five exons and four introns
Summary
Proteins with particular glycine-rich regions have been reported in seed coat and cell wall of a wide variety of plants; for example, soybean seed coat contains 21% of glycine, the cell wall of milkweed stem has 31%, and coat coleoptile cells have 27% of glycine (de Oliveira et al, 1990). Glycine-rich proteins (GRPs) have been isolated from pumpkin seed coat (Varner and Cassab, 1986) and strawberry fruit (Reddy and Poovaiah, 1987) with approximately 47% and 49% glycine residues, respectively. Five groups of GRPs [i.e., (I) (GGX)n, (II) (GGXXXGG)n, (III) (GXGX)n, (IV) glycine-rich domain with additional motifs such as RNA-recognition motif (RRM) or a coldshock domain (CSD), CCHC zinc-fingers and (V) GGX/GXGX] have been suggested based on the general structure and the arrangement of the repeated glycine signatures as well as the presence of conserved motifs and domains (Bocca et al, 2005; Mangeon et al, 2010; Ortega-Amaro et al, 2014). Overexpression of alfalfa GRP leads to salt and ABA sensitivity in Arabidopsis thaliana (Long et al, 2013)
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