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Investigation of the role of cell-cell interactions in division plane determination during maize leaf development through mosaic analysis of the tangled mutation

Section of Cell and Developmental Biology, U.C. San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0116, USA

View larger version (240K): [in a new window]   Fig. 1. Epidermal layers of wild-type and tan mutant leaves. (A) Scanning electron micrograph (SEM) of the surface of a wild-type maize leaf primordium. Shallow indentations in the leaf surface are indicative of recent cell divisions. Horizontal arrows point to several recent transverse divisions. Vertical arrows point to several recent longitudinal divisions. (B) SEM of the surface of a tan mutant leaf primordium. Arrows point to several recent abberant divisions. Scale bars in A and B: 100 µm. (C) Epidermal peel from mature, wild-type leaf illustrating a characteristic regular cell pattern. (D) Epidermal peel from a mature, tan mutant leaf illustrating a chaotic cell pattern. Arrows point to aberrantly positioned walls in interstomatal cells that were factored into calculation of abnormality index as described in Materials and Methods. Scale bar in C: 100 µm for C and D.

View larger version (6K): [in a new window]   Fig. 2. Diagram of a hypothetical leaf in cross-sectional view illustrating all possible types of sector boundaries. Upper and lower epidermises are demarcated by closely spaced horizontal lines, and are separated by multiple mesophyll layers. Shaded areas represent wild-type tissue; unshaded areas represent w14-marked tan mutant tissue. Wild-type epidermal cells may overlie wild-type mesophyll (A) or mutant mesophyll (B). Mutant epidermal cells may overlie mutant mesophyll (C) or wild-type mesophyll (D). Transverse sector boundaries between the epidermis and mesophyll occur when wild-type epidermal cells overlie mutant mesophyll (e.g., area B) or when mutant epidermal cells overlie wild-type mesophyll (e.g., area D). Lateral sector boundaries in the epidermis are represented by numbered arrows. A lateral boundary in the epidermis may coincide directly with a lateral boundary in the mesophyll (arrow 2). It may also occur over either wild-type (arrow 1) or mutant (arrow 3) mesophyll.

View larger version (119K): [in a new window]   Fig. 3. Phenotype observed at lateral sector boundaries in the epidermis. Epidermal and mesophyll genotypes are indicated to the left and right of each sector boundary (i.e., wt/wt means the epidermis and underlying mesophyll are both wild type; wt/mut means the epidermis is wild type and the underlying mesophyll is mutant, etc.). White asterisks indicate wild-type guard cells containing chloroplasts. Black asterisks indicate mutant guard cells lacking chloroplasts. Black arrows indicate oblique cell walls immediately adjacent to marked, wild-type cells. Note that the wild-type cells adjacent to these walls are of normal shape. White arrows indicate aberrantly divided wild-type cells. For regions where the interval between wild-type and mutant stomatal files is 2 or fewer cell files, numbered black arrowheads indicate the distance between the two files. (A,B) Lateral sector boundaries in the epidermis coinciding with lateral boundaries in the underlying mesophyll. Note the sharp transition between wild-type and mutant-appearing cells regardless of the distance between the stomatal files marking the boundary region. (C) Lateral sector boundary in the epidermis overlying wild-type mesophyll. Note that the phenotypes of mutant cells overlying wild-type mesophyll (lower right quadrant) are comparable to those of mutant cells overlying mutant mesophyll in A, B and D. (D) Lateral sector boundary in the epidermis overlying mutant mesophyll. Note that wild-type epidermal cells overlying mutant mesophyll (left half) appear as regular as those overlying wild-type mesophyll in A, B and C. Scale bar in A:100 µm for A-D.

View larger version (10K): [in a new window]   Fig. 4. Proximity of mutant and non-mutant stomatal files marking the boundary region. The number of cell files separating individual wild-type stomata from the nearest mutant stoma was counted for a total of 453 stomatal pairs. For 0 files, n=13; 1 file, n=36; 2 files, n=83; 3 files, n=141; 4 files, n=107; 5 or more files, n=73.

View larger version (12K): [in a new window]   Fig. 5. Abnormality index calculated for mutant epidermal cells overlying mutant mesophyll or wild-type mesophyll, or near a lateral sector boundary in the epidermis (see Materials and Methods for methodology). (A) Stomatal files. (B) Adjacent, non-stomatal files. Error bars show standard deviations.

View larger version (11K): [in a new window]   Fig. 6. Abnormality index calculated for wild-type epidermal cells overlying wild-type mesophyll or mutant mesophyll, or near a lateral sector boundary in the epidermis (see Materials and Methods for methodology). Note that for 5 of the 6 transverse boundaries included in this analysis having wild-type epidermal cells overlying mutant mesophyll, all mesophyll layers were mutant. (A) Stomatal files. (B) Adjacent, non-stomatal files. Error bars show standard deviations.