臨時生物科学セミナー（第１６３回）

　日　時：平成２０年９月１７日（水）　�@１５：００〜１６：３０

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場　所：理学部２号館　第二講義室（２２３号室）

�@１５：００〜１６：３０

講演題目：Lessons from a search for leaf mutants in Arabidopsis thaliana

講演者名：José Luis Micol教授

División de Genética and Instituto de Bioingeniería, Universidad Miguel Hernández de Elche, 03202 Elche, Alicante, Spain

Large-scale exploratory approaches to understanding gene function laid the foundations for the “-omics era”. Based on modern technologies for the structural and functional characterization of genomes, these curiosity-driven approaches allow systematic accumulation of vast amounts of data, enabling subsequent hypothesis-driven research. Some years before the dawn of genomics, however, exploratory approaches were already furthering our understanding of gene function in the form of saturation mutagenesis experiments aimed at the identification of all genes that mutate to a given phenotype. Forward genetic approaches, conducted on experimental organisms such as Drosophila melanogaster and Caenorhabditis elegans, have led to the isolation of mutants affected in specific developmental processes, whose cellular and molecular characterization has unraveled the underlying genetic mechanisms of animal development.

To shed light on the making of plant leaves, in 1993 we initiated an attempt to identify as many viable and fertile mutants with abnormal leaf morphology as possible, using the Arabidopsis thaliana model organism. We identified 28 fast-neutron- and 153 ethyl-methane sulfonate-induced mutations, which fell into 8 and 94 complementation groups, respectively¹. We also studied 115 publicly available mutant lines isolated by previous authors, which fell into 37 complementation groups². Although we did not reach saturation of the Arabidopsis thaliana genome, the broad spectrum of leaf morphological alterations identified is facilitating the dissection of specific leaf developmental processes. In a complementary approach, we also analyzed leaf architecture in natural accessions and two populations of recombinant inbred lines^3,4. Using a high-throughput gene mapping method^5,6, we have already cloned 31 of the genes identified by mutation, in some cases in collaboration with other groups. The products of these genes participate in various developmental processes, such as polar cell expansion, transduction of hormonal signals, gene regulation, plastid biogenesis, and chromatin remodeling, among others. The range of phenotypes and processes identified reveal the complexity of leaf ontogeny and will help explain the diversity of leaf morphology in nature.

References:

1. Berná, G., Robles, P., and Micol, J.L. (1999). Genetics 152, 729-742.

2. Serrano-Cartagena, J., Robles, P., Ponce, M.R., and Micol, J.L. (1999). Mol. Gen. Genet. 261, 725-739.

3. Pérez-Pérez, J.M., Serrano-Cartagena, J., and Micol, J.L. (2002). Genetics 162, 893-915.

4. Juenger, T., Pérez-Pérez, J.M., Bernal, S., and Micol, J.L. (2005). Evol. Dev. 7, 259-271.

5. Ponce, M.R., Robles, P., and Micol, J.L. (1999). Mol. Gen. Genet. 261, 408-415.

6. Robles, P., and Micol, J.L. (2001). Mol. Gen. Genomics 266, 12-19.

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講演題目：A phenomics platform for the characterization of Arabidopsis leaf mutants

講演者名：Pérez-Pérez, J.M博士

División de Genética and Instituto de Bioingeniería, Universidad Miguel Hernández, Campus de Elche, 03202 Elche, Alicante, Spain.

A large number of mutants with visible and viable phenotypes have been obtained from forward genetic approaches for the dissection of Arabidopsis development. Examples are several large-scale screens for mutations affecting leaf shape and size (Berná et al., 1999; Serrano-Cartagena et al., 1999; Horiguchi et al., 2006). In addition, reverse genetic approaches have been made possible by the availability of thousands of lines carrying T-DNA insertions. Over 400,000 independent T-DNA insertion events have been mapped into the Arabidopsis genome and about 10,000 lines homozygous for single T-DNA insertions have been produced (http://signal.salk.edu/). We performed a morphometric analysis of several rosette and leaf parameters in 111 lines previously identified as leaf mutants, what would allow us to establish a numeric framework for leaf phenotype comparisons and their tabulation. A similar approach will be used for the analysis of the SALK collection of sequence-indexed homozygous insertion mutants.

References:

Berná, G., Robles, P., and Micol, J.L. (1999). A mutational analysis of leaf morphogenesis in Arabidopsis thaliana. Genetics 152, 729-742.

Horiguchi, G., Ferjani, A., Fujikura, U., and Tsukaya, H. (2006). Coordination of cell proliferation and cell expansion in the control of leaf size in Arabidopsis thaliana. J. Plant Res. 119, 37-42.

Serrano-Cartagena. J., Robles. P., Ponce, M.R., and Micol, J.L. (1999). Genetic analysis of leaf form mutants from the Arabidopsis Information Service collection. Mol. Gen. Genet. 261, 725-739.

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