SummaryIt is during embryogenesis that the body plan of the developing plant is established. Analysis of gene expression during embryogenesis has been limited due to the technical difficulty of accessing the developing embryo. Here we demonstrate that laser capture microdissection can be applied to the analysis of embryogenesis. We show how this technique can be used in concert with DNA microarray for the large-scale analysis of gene expression in apical and basal domains of the globular-stage and heart-stage embryo, respectively, when critical events of polarity, symmetry and biochemical differentiation are established. This high resolution spatial analysis shows that up to approximately 65% of the genome is expressed in the developing embryo, and that differential expression of a number of gene classes can be detected. We discuss the validity of this approach for the functional analysis of both published and previously uncharacterized essential genes.

Efforts to understand laser bioeffects in cells and tissues have been hindered by a nonuniform cellular response of the specimen, resulting in graded biochemical effects. In addition, the small beam diameters of commonly used lasers limit the number of cells expressing a response to numbers inadequate for the study of biochemical effects. For a limited emission power, expansion of the beam diameter reduces the irradiance, thus requiring longer exposure durations to produce a cellular response. Cultured human retinal epithelial cells were exposed as a single spot ("tophat" exposure) from a carbon dioxide (CO 2) laser operating at 10.6 m or scanned with a raster system and compared with thermal injury produced with heated saline for short periods (1-9 s) at relatively high temperature (55-70°C). Cell viability and induction of the 70 kDa heat shock protein were evaluated as indicators of the cellular response. Initial attempts to use a tophat (uniform energy distribution) exposure resulted in a nonuniform cellular response (and nonuniform energy distribution) due to diffraction effects from the 2-mm selection aperture. However, raster scanning for appropriate times with the CO 2 laser yielded uniform cell viability and heat shock protein synthesis that were comparable to dipping cells in heated saline. Because scanning results in a homogeneous exposure of cells, the described scanning technique may be applied to studies of cellular responses to other lasers to evaluate photochemical and photomechanical effects.carbon dioxide laser LASERS ARE INCREASINGLY FOUND in medical applications particularly in the area of eye surgery being used for photocoagulation and refractive surgery. Along with this increased use comes the elevated possibility of injury from their use and the need for methods to ameliorate these injuries. In the effort to understand laser-tissue interactions, a variety of animal models have been examined (12,17,19,20). Much has been learned about how laser light can damage biologic tissue, especially the retina. However, most of what we know from animal models is based on morphological data (7-13). Because the injuries are small and result in poor signal-to-noise ratios of any released biochemical/molecular signals, biochemical and molecular data have not been obtained. Therefore it has been difficult to formulate therapeutic measures based on a thorough understanding of the underlying injury. The objective of this study, therefore, is to design a means of producing a uniform injury so that a homogeneous response to laser exposure could be obtained with sufficient numbers of cells to facilitate analysis at the molecular level.Retinal pigment epithelial (RPE) cell changes are observed by histopathology after visible laser exposure at doses near the ophthalmoscopic minimal visible lesion threshold for exposure conditions where the interaction mechanism is photothermal (8). Collimated, visible laser light incident upon the cornea is transmitted through the outer ocular media and imaged or focused onto the ...