Abstract
In plants, the first asymmetrical division of a zygote leads to the formation of two cells with different developmental fates. The establishment of various patterns relies on spatial and temporal gene expression, however the precise mechanism responsible for embryonic patterning still needs elucidation. Auxin seems to be the main player which regulates embryo development and controls expression of various genes in a dose-dependent manner. Thus, local auxin maxima and minima which are provided by polar auxin transport underlie cell fate specification. Diverse auxin concentrations in various regions of an embryo would easily explain distinct cell identities, however the question about the mechanism of cellular patterning in cells exposed to similar auxin concentrations still remains open. Thus, specification of cell fate might result not only from the cell position within an embryo but also from events occurring before and during mitosis. This review presents the impact of auxin on the orientation of the cell division plane and discusses the mechanism of auxin-dependent cytoskeleton alignment. Furthermore, close attention is paid to auxin-induced calcium fluxes, which regulate the activity of MAPKs during postembryonic development and which possibly might also underlie cellular patterning during embryogenesis.
Highlights
Embryogenesis is driven by sophisticated and orchestrated processes which are kept under the control of various molecular pathways
This review presents cytophysiological responses to auxin which affect cytoskeleton alignment, and show that gene expression may contribute to cellular patterning
Cellular patterning, which starts with the first division of a zygote, seems to be executed by regulation of different gene expression and through factors which control the direction and the symmetry of cell division
Summary
Embryogenesis is driven by sophisticated and orchestrated processes which are kept under the control of various molecular pathways. Phenotypic analyses of mutants and studies with the use of protein inhibitors provide clear evidence that three molecular pathways are indispensable for a correct embryo development, and these include polar auxin transport, mitogen-activated protein kinases and DNA methylation. Dysfunction of these molecular pathways leads to embryogenesis disorders and may be lethal for the developing embryo [1,2,3]. A zygote elongates in micropylar-chalzal axis and divides asymmetrically In this way the extraordinary process begins which leads to development of the functional embryo [4,5,6]. This review presents cytophysiological responses to auxin which affect cytoskeleton alignment, and show that gene expression may contribute to cellular patterning
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