| In order to study the molecular mechanisms of leaf vein patterning in the context of leaf development and patterning as well as the relationship between vein patterning and the plant hormone auxin, we have taken a forward genetic approach to isolate genetic components of the leaf vein patterning process.;We positionally cloned two previously identified mutants from a DEB-mutagenized Arabidopsis thaliana population. The parallel1 ( par1) and paralle12 (par2) mutant juvenile leaves have a parallel vein appearance as their veins are aligned more along the proximal/distal leaf axis, anastomose at the leaf base, and display reduced higher order venation. PAR1 is important for the proper spatial localization of responses to the plant hormone auxin and encodes a nucleolin involved in ribosomal RNA processing. PAR2 encodes a plant-specific protein of the NPH3/RPT2 family and is closest to the founding family member NPH3, which is known to be involved in auxin-dependent phototropic responses.;We also performed both activation and Dissociation/Activation (Ds/Ac) transposon tagging screens and identified 12 and 17 phenotypic lines with vein patterning defects in juvenile leaves, respectively. We grouped these lines into five classes and use them to evaluate the predictability of proposed vein patterning models. One of the phenotypic lines, line 21350, was determined to be allelic to a previously identified mutant, while another novel line, line 4328/extra marginal veins1 (exv1), was initially characterized and cloned. EXV1 encodes a putative zinc finger transcription factor and may be involved in the polar transport of auxin.;Signaling, transport, and response of the plant hormone auxin are now even more clearly and strongly connected to patterning processes than ever. Since many models of vein patterning have been proposed based upon a connection to auxin, we consider the predictability of these models using the phenotypes we isolated. Further, the genes cloned in this thesis join the list of vein patterning genes that appear disconnected at the molecular level. Thus, we discuss the possibility that connections between vein patterning genes that have seemingly disparate molecular functions may be made through auxin. |
