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Molecular and genetic analyses of the Bel1 gene regulating ovule development in Arabidopsis thaliana

University of British Columbia

Phenotypic characterization of the Arabidopsis thaliana mutant Bel1 revealed numerous morphological abnormalities of Bel1 ovules, including the absence of the inner integuments, homeotic transformation of the outer integuments into carpel-like structures, and incomplete development of the female gametophytes. The homeotic transformation of outer integuments into carpelloid structures in Bel1 has been correlated with abnormal expression of class C gene expression in the Arabidopsis ovule. Both direct and indirect evidence established such correlation: first, transcripts of AGAMOUS, the only class C gene identified to date, were detected throughout Bel1 ovules at the time of formation of carpel-like structures and second, the highest frequency of carpel-like structures was found in Bel1 plants grown under environmental conditions that also stimulate class C function. These data suggested that the BEL1 product functions as a negative regulator of AG during ovule development. Similar to Bel1, occasional transformation of ovules into structures with carpelloid features occurs in Ap2-6 mutant plants, indicating a role of the APETALA2 gene in ovule development not previously described. AP2 function during early Arabidopsis flower development is to suppress AG in the outermost whorls. My data suggests that AP2 functions in a similar manner during ovule development. Two mutant alleles, bel1-2 and bel1-3, originate from Agrobacterium T-DNA mutagenized populations of Arabidopsis and both of them are due to T-DNA insertions into the BEL1 locus. Genomic sequences adjacent to the T-DNA insert in the bel1-2 were used to isolate the putative BEL1 gene (L. Reiser and R. Fischer, unpublished data). The identity of the cloned BEL1 sequence was confirmed by cloning the bel1-3 allele and demonstrating that the T-DNA lies within putative BEL1 gene and by complementation of the Bel1 mutant phenotype with the cloned sequence. Characterization of the BEL1 gene revealed its amino acid sequence identity to DNA binding domain of the homeobox family of transcription factors, suggesting that the BEL1 protein itself may function as a transcriptional regulator. The search for genes homologous to BEL1 resulted in identification of three new homeobox genes, ABH1, ABH2, and ABH3. Together with BEL1, these three genes define a novel homeobox gene subfamily in Arabidopsis.

Thesis/Dissertation

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2009-06-09

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http://hdl.handle.net/2429/8873

Botany

University of British Columbia

UBCV

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