Genetic analysis of ovule development and seed coat mucilage production in arabidopsis thaliana

• Main Author: Western, Tamara Lynn
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/9608

Recently, many genes involved in the regulation of ovule development have been identified in Arabidopsis thaliana. One of diese genes is BEUL1 (BEEi), which is involved in the production of ovule integuments and is thought to work at least partially through the suppression of the floral organ identity gene, AGAMOUS (AG). A new investigation of the genetic interactions between BEL.1 and AG has shown that both genes have active roles throughout ovule morphogenesis. BEL.1 and AG act early in ovule development in a partially redundant manner to direct ovule identity. The abnormal integument development characteristic of the Bell mutant phenotype was found to be dependent on AG function, suggesting that BEL.1 and AG work in combination to promote normal integument morphogenesis. Finally, BEL1 appears to be required for embryo sac development independent of other aspects of ovule morphogenesis and AG function. Another floral organ identity gene that is thought to act in ovule development is APETAEA2 (AP2). This has been confirmed through quantitation of ovule phenotypes in multiple alleles, which revealed that in the absence of AP2 function there is sporadic production of multiple types of abnormal ovules. These data suggest that AP2 may stabilize developmental decisions throughout ovule development. During seed development, many plants synthesize and secrete a vast quantity of pectin in the form of mucilage between the plasma membrane and outer cell wall of their epidermal cells. The production of mucilage during Arabidopsis seed coat development was studied and then exploited in a novel screen for mutants defective in polysaccharide synthesis, deposition, and extrusion. Mutations in five novel genes, MUCILAGE-MODIFIED (MUM) 1—5 were isolated, and were studied along with mutants defective in four previously identified loci that affect seed coat development (TRANSPARENT TESTA GLABRA1 [TTG1], GLABRA2 [GU], ABERRANT TESTA SHAPE [ATS], and AP2). The phenotypes of the mutants suggest that AP2 and ATS regulate general seed coat development, while MUM4, TTG1, and GL2 affect the epidermal cell structure and mucilage amount. In addition, MUM3 and MUM5 control mucilage composition, and MUM1 and MUM2 affect its extrusion beyond the outer cell wall.