The role of cell cycling during vascular development in leaves of Arabidopsis thaliana.

摘要

The goals of my thesis were: (1) to characterize the expression of pAtHB-8::GUS during procambial strand formation; (2) to determine the spatial patterns of cell proliferation in developing vascular strands and; (3) to determine if modification of cell proliferation alters leaf vascular architecture.; For a properly functioning vascular system, a continuous, hierarchical vein system must be in place. Characterization of the expression of p AtHB-8::GUS was used to identify procambium and its course of development. Observations reveal that AtHB-8 is expressed early identifying a pre-procambial stage. These strands of cells develop progressively through the recruitment of ground meristem cells to their termini. The procambial vein pattern is formed approximately 4 days earlier than that of differentiated xylem. Expression of AtHB-8 however, is not observed in late-formed higher order veins, suggesting that regulation of vein pattern does not strictly require AtHB-8.; Cell cycling is an important aspect of leaf histogenesis because of its role in the distinctive planes of cell division and differential patterns of cell proliferation. Using a molecular marker of cell division, p CYCB1::GUS, to assess cell proliferation patterns during vascular development, I found that vein orders are remodeled through differential patterns of cell proliferation. This pattern underlies the formation of vein size hierarchy during vascular development. The overlapping expression pattern of p AtHB-8::GUS and pCYCB1;1::GUS suggests that AtHB-8 may regulate the distinctive patterns of cell division that distinguish procambium from surrounding ground meristem as well as regulating cell proliferation of the procambial cells.; To assess the role of cell proliferation during vein order formation, genetic lines that exhibit aberrant cell proliferation patterns due to altered expression patterns of ANT, ICK, and CYCD3;1 genes were analyzed. Altering the pattern of cell proliferation does not affect the longitudinal pattern of major veins but does affect minor vein order hierarchy and total vein cell number. When cell proliferation is reduced, the premature timing of mesophyll cell expansion correlates with the formation of freely ending veinlets. Expression of these genes is localized to procambial cells, suggesting that these genes could play a role in maintaining meristematic competence of procambial cells during vascular development.