Relationship between Endopolyploidy and Cell Size in Epidermal Tissue of Arabidopsis.

Abstract

Relative quantities of DNA in individual nuclei of stem and leaf epidermal cells of Arabidopsis were measured microspectrofluorometrically using epidermal peels. The relative ploidy level in each nucleus was assessed by comparison to root tip mitotic nuclei. A clear pattern of regular endopolyploidy is evident in epidermal cells. Guard cell nuclei contain levels of DNA comparable to dividing root cells, the 2C level (i.e., one unreplicated copy of the nuclear DNA). Leaf trichome nuclei had elevated ploidy levels of 4C, 8C, 16C, 32C, and 64C, and theircytology suggested that the polyploidy represents a form of polyteny. The nuclei of epidermal pavement cells were 2C, 4C, and 8C in stem epidermis, and 2C, 4C, 8C, and 16C in leaf epidermis. Morphometry of epidermal pavement cells revealed a dimct pmportionality between nuclear DNA level and cell size. A consideration of the development process suggests that thecellsof highest ploidy level are developmentally oldest; consequently, the developmental pattern of epidermal tissues can be read fmm the ploidy pattern of the cells. This observation is relevant to theories of stomate spacing and offers opportunities for genetic analysis of the endopolyploidylpolyteny phenomenon.

Tissue-specific Expression and Dynamic Organization of SR Splicing Factors inArabidopsis

“…Differences exist among cell types with regard to speckle number, size, density, and ratio of signal intensities between speckles and the nucleoplasm (Figure 2). We also observed a positive relationship between cellular size, nuclear volume, and ploidy level, similar to previous findings (Baluska, 1990;Melaragno et al, 1993;Kato and Lam, 2003).Small LEP (Figure 2, C, CЈ, and CЉ), sepal (Figure 2, E, EЈ, and EЉ), and petal (Figure 2, F, FЈ, and FЉ) epidermal pavement cells have the same 2C ploidy level as guard cells (Figure 2, D, DЈ, and DЉ) and RM (Figure 2, G, GЈ, and GЉ) (Melaragno et al, 1993), but the latter have more diffuse signals of the expressed splicing factors. The localization patterns are also different in certain cell types for the three splicing factors; for example, in small leaf epidermal, sepal, and petal epidermal pavement cells, atSRp30 (Figure 2, CЉ, EЉ, and FЉ) is more diffuse than SR1/atSRp34 (Figure 2, CЈ, EЈ, and FЈ) and SR33 (Figure 2, C, E, and F).…”

“…Small LEP (Figure 2, C, CЈ, and CЉ), sepal (Figure 2, E, EЈ, and EЉ), and petal (Figure 2, F, FЈ, and FЉ) epidermal pavement cells have the same 2C ploidy level as guard cells (Figure 2, D, DЈ, and DЉ) and RM (Figure 2, G, GЈ, and GЉ) (Melaragno et al, 1993), but the latter have more diffuse signals of the expressed splicing factors. The localization patterns are also different in certain cell types for the three splicing factors; for example, in small leaf epidermal, sepal, and petal epidermal pavement cells, atSRp30 (Figure 2, CЉ, EЉ, and FЉ) is more diffuse than SR1/atSRp34 (Figure 2, CЈ, EЈ, and FЈ) and SR33 (Figure 2, C, E, and F).…”

“…The localization patterns are also different in certain cell types for the three splicing factors; for example, in small leaf epidermal, sepal, and petal epidermal pavement cells, atSRp30 (Figure 2, CЉ, EЉ, and FЉ) is more diffuse than SR1/atSRp34 (Figure 2, CЈ, EЈ, and FЈ) and SR33 (Figure 2, C, E, and F). The nuclei of larger LEP are enlarged and elongated with an irregular oval shape deformed by vacuoles or chloroplasts (Figure 2A), and their ploidy levels vary from 4C to 8C (Melaragno et al, 1993). Trichomes, the largest cell type, have the largest nuclei with irregular oval shapes ( Figure 2B) and ploidy levels up to 64C (Melaragno et al, 1993).…”

“…However, the expression of atSRp30-YFP in leaves is weak and below the detection sensitivity of CLSM at these equalized settings ( Figure 1M). The nuclei of three distinct cell types in leaf epidermis, guard cells (Gu), leaf epidermal pavement cells (LEP), and trichomes (Tri), are highlighted with arrows ( Figure 1, C and H) (Melaragno et al, 1993).In inflorescence stems, the strongest signals were observed in SR1-YFP-expressing plants ( Figure 1J), whereas SR33 ( Figure 1E) is stronger than that of atSRp30 ( Figure 1O). In flowers, all three SR proteins have high expression in the pollen grains (Figure 1, D, I, and N) with signals in vegetative nuclei ( Figure 1DЈ, arrow) much stronger than that observed in nuclei of sperm cells ( Figure 1DЈ, arrowheads).…”

The Sink-Specific Plastidic Phosphate Transporter PHT4;2 Influences Starch Accumulation and Leaf Size in Arabidopsis

“…To determine whether the enlargement of pht4;2 leaves was associated with increased cell number, cell size, or a combination of these parameters, we compared the ninth rosette leaves of pht4;2 and wild-type plants at different stages of leaf expansion (Table III). When plants were grown Repeated cycles of endoreduplication give rise to somatic polyploidy, which is positively correlated with cell and leaf size (Melaragno et al, 1993;Vlieghe et al, 2005). However, endoreduplication appears to be unaffected by the loss of PHT4;2, because the distribution of ploidy levels in cells of mature pht4;2 and wild-type leaves was nearly identical (Supplemental Fig.…”