Leaf nuclei are lens shaped; thus, the projection area of the nucleus correlates negatively with the rate of nuclear positioning at the anticlinal wall (Iwabuchi et al
August 12, 2021
Leaf nuclei are lens shaped; thus, the projection area of the nucleus correlates negatively with the rate of nuclear positioning at the anticlinal wall (Iwabuchi et al., 2016). reduced in number, which led to pleiotropic defects in nuclear morphology, cytoplasmic streaming, and herb growth. The mutation in caused aberrant positioning of nuclei-associated actin filaments at the anticlinal walls. AN was detected in the cytosol, where it interacted actually with plant-specific dual-specificity tyrosine phosphorylation-regulated kinases (DYRKPs) and itself. The DYRK inhibitor (1and mutants indicates that dark-induced nuclear positioning is differentially regulated between pavement cells and mesophyll cells (Iwabuchi et al., 2007, 2010, 2016). Here, we screened for mutants defective in nuclear position in the dark to identify additional regulatory proteins involved in dark-induced nuclear positioning. We obtained two impartial mutants, which we designated (is usually a previously unreported dominant-negative mutant of is usually a recessive mutant of the gene (encodes a herb homolog of C-terminal-binding protein/brefeldin A-ADP ribosylated substrate (CtBP/BARS; Folkers et al., 2002; Kim et al., 2002). AN is usually involved in determining leaf and cell designs, root formation, microtubule business, and abiotic stress responses in Arabidopsis (Tsuge et al., 1996; Folkers et al., 2002; Kim et al., 2002; Bai et al., Peimine 2013; Gachomo et al., 2013; Bhasin and Hlskamp, 2017). Our findings reveal the relationship between AN and the actin cytoskeleton in centripetal nuclear positioning in Arabidopsis leaves. RESULTS Isolation of Two Arabidopsis Mutants with Defects in Nuclear Positioning in the Dark To explore the mechanism of dark-induced nuclear positioning, we employed a forward genetics approach. We isolated the mutant by screening an ethyl methanesulfonate-mutagenized populace of transgenic Arabidopsis plants expressing the nuclear marker Nup50a-GFP (Tamura et al., 2013). In dark-adapted wild-type leaves, most nuclei in palisade mesophyll and pavement cells were situated at the inner periclinal wall of the cell. In leaves, by contrast, 52% of nuclei were aberrantly positioned at the anticlinal walls of mesophyll cells, although most nuclei in pavement cells were positioned at the inner periclinal walls, as in wild-type cells (Fig. 1). Leaf nuclei are lens shaped; thus, the projection area of the nucleus correlates Peimine negatively with the rate of nuclear positioning at the anticlinal wall (Iwabuchi et al., 2016). This was observed in mesophyll cells (Supplemental Fig. S1). Open in a separate window Physique 1. The and mutants exhibit aberrant nuclear Peimine positioning in the dark. A, Distribution patterns of nuclei in palisade mesophyll cells and adaxial pavement cells of wild-type, leaves in the dark. The left Peimine and middle columns show horizontal sections with nuclei (blue) stained with Hoechst 33342. Cells are layed out with yellow dotted lines. The right column shows cross sections, including nuclei (green) stained with Hoechst 33342, cell walls (blue) stained with Calcofluor, and chloroplasts (magenta). Bars = 20 m. B, TNFRSF1B Percentage of nuclei positioned on the anticlinal walls of palisade mesophyll and adaxial pavement cells of wild-type, leaves in the dark and after illumination with blue light (100 mol m?2 s?1 for 3 h). Data symbolize means se (= 5 leaves; **, < 0.01 with Students test). Mesophyll and pavement cells were observed in each of five leaves from different plants; the mean numbers of each cell type observed per leaf were as follows: wild-type leaves, 100 mesophyll and 67 pavement cells; leaves, 103 mesophyll and 49 pavement cells; and leaves, 135 mesophyll and 88 pavement cells. Nuclear positioning after exposure to 100 mol m?2 s?1 blue light for 3 h also was investigated in nuclei moved to the anticlinal walls, although in mesophyll cells, 87% of wild-type nuclei and 83% of nuclei moved to the anticlinal walls (Fig. 1B; Supplemental Fig. S2). These results indicate that this mutation affected blue light-induced nuclear positioning in pavement cells. We also observed the positions of chloroplasts in mesophyll cells and found no differences between the wild type and mutation did not appear to impact chloroplast positioning. The leaf petioles of the mutant were bent upward (Supplemental Fig. S3A), and herb height, seed number per fruit, and fruit length were reduced significantly in compared with wild-type plants (Supplemental Fig. S3, BCD). Furthermore, the nuclei of pavement cells were spherical, while those of wild-type cells were spindle shaped (Supplemental Fig. S3E). The nuclei of and wild-type cells were almost the same size (Supplemental Fig. S3F). These data show that, in addition to changes in nuclear positioning, the mutant exhibited pleiotropic phenotypes in various organs. We isolated the mutant from an Arabidopsis populace transporting T-DNA insertions. Dark-induced nuclear positioning was impaired in pavement and mesophyll cells of leaves; 65% of mesophyll nuclei and 36% of pavement nuclei were positioned aberrantly at the anticlinal walls (Fig. 1), indicating that the mutation affected a gene.