Genetic pathways of meristem and leaf development in Arabidopsis thaliana

Abstract

Unlike metazoan systems, plants sustain growth throughout their life by the division of undifferentiated populations of stem cells called meristems. Of these meristematic regions, the shoot apical meristem (SAM) produces the entire above ground structure of plants including branches, leaves and flowers. Initiation and function of the SAM is controlled in part, by transcription factors called three-amino-acid-loop-extension (TALE) homeodomain proteins. The TALE homeodomain proteins consist of two categories: 1) BEL1-like homeodomain proteins (BLH) and 2) KNOTTED1-like homeodomain (KNOX) proteins. The BEL1-like protein BELLRINGER, has been shown to have roles in SAM identity, function, secondary organ development and shoot architecture. The BLH1 gene has been shown to have roles in embryo sac development, ABA-mediated seed dormancy and early seedling development. BLH proteins convey their roles in development through dimerization with KNOX proteins and although our knowledge on KNOX genes is increasing, we know relatively little about BLH genes. Here we investigated the role of BLH3, BLH6, BLH7, and BLH11 using reverse genetics and reporter gene expression analysis. We found no obvious phenotype was associated with single, double or triple mutant plants for the genes studied although some stem and phyllotaxis phenotypes appeared in overexpression lines. We suggest that there may be redundancy between the genes we studied and other members of this family and/or other gene families. Moreover, for future investigations, we suggested that our mutants can have phenotypes at the microscopic levels specifically in the cell wall and vasculature. Keywords: Shoot Apical Meristem (SAM); Leaf Formation; Developmental Genetics; TALE; Transcription Factors