Evolutionary developmental genetics of fruit opening in Brassicaceae

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The aim of the project is to better understand the developmental genetic basis and ecological implications of the recurrent transition from dehiscent to indehiscent fruits during the evolution of Brassicaceae, using Lepidium campestre (dehiscent) and L. appelianum (indehiscent) as model systems. In the previous phase of the project we identified a change in the expression of the L. appelianum APETALA2 (AP2) ortholog which has probably caused the loss of dehiscence zone formation via the repression of dehiscence zone identity genes. To better understand the role of AP2 in the evolution of indehiscence we will characterize the genomic sequences and expression patterns of this locus in A. thaliana, L. campestre and L. appelianum. We will also determine whether over-expression of cDNA of any of the AP2 orthologs in A. thaliana and L. campestre is sufficient to transform dehiscent into indehiscent fruits. Moreover, we will transform the genomic loci of the AP2 orthologs into both wild-type and ap2 knock-out plants and will observe which transgenic plants develop dehiscent or indehiscent fruits. This will reveal whether the AP2 locus contains the causative mutation of fruit indehiscence. In addition, we also will compare the transcriptomes of dehiscent and indehiscent fruits to get a more comprehensive picture of the gene regulatory differences between these fruit types. In yet another branch of the project we will analyze the consequences of fruit indehiscence for seed and fruit dispersal and germination timing mechanisms. We will determine if seeds of dehiscent and indehiscent fruits differ in dormancy and germination, and whether abrasion of the pericarp, fire, or fungal assistance are involved in pericarp-mediated dormancy release in indehiscent fruits. Finally, we will determine whether differences in glucosinolate patterns of dehiscent and indehiscent fruits represent different modes of defense associated with different dispersal strategies.