Gene regulation and evolution in ovules

To help define the elements responsible for regulation of INNER NO OUTER (INO), a critical regulator of ovule development in Arabidopsis, and to examine the conservation and divergence of such elements, promoter regions were isolated from INO orthologs from Lycopersicon esculentum and Brassica oleracea .; Comparisons between the Brassica and Lycopersicon promoter sequences relative to Arabidopsis identified regions of conservation between Brassica and Arabidopsis promoters in regions previously found to be functionally important. Smaller regions of conservation were identified between Arabidopsis and Lycopersicon. Reporter constructs (GFP) made with the Brassica and Lycopersicon INO promoters and transformed intoArabidopsis and Lycopersicon gave similar fluorescence patterns to in-situ hybridization results.; In in-situ hybridization experiments with Lycopersicon INO (LeINO) , expression is confined to the outer layer of the single integument. Constructs to complement the Arabidopsis ino mutation using LeINO or AtINO under the promotion of the Lycopersicon INO promoter were unable to complement the mutation. LeINO is also unable to complement the Arabidopsis ino mutation fused to the Arabidopsis INO promoter.; The Santalales (an order of mainly parasitic plants that includes mistletoe and sandalwood) includes species with ovules similar to those found in most other angiosperms (bitegmic), but also has members with extremely reduced ovules compared with the rest of the angiosperms. For some species one or both integuments are absent (unitegmic or ategmic) and in others, ovules are not seen to emerge from the underlying placental tissues (characterized as not being true ovules).; Ovules of four types were studied in the Santalales: bitegmic, unitegmic, ategmic, and those characterized as having no true ovules with the goal of defining the nature of the reductions. It was found that the published morphologies were the same as those observed for all species with the exception of Phoradendron flavescens which has ategmic ovules rather than no ovules.; In examining the expression of orthologs of two ovule genes characterized in Arabidopsis thaliana, AINTEGUMENTA (ANT) and BELL1 (BEL1), were expressed in all the ovules examined. We hypothesize that ategmic ovules derive from a fusion of the integuments with the nucellus.