Gregor Johann Mendel presented Laws of Heredity and Law of Dominance in 1865.  When copies of each dominant and recessive allele are inherited from each parent, a dominant one determines a phenotype, which is known as Laws of Heredity.  It has been understood that recessive alleles lose its function.

 In this study, we focused on dominant/recessive relationships between multiallelic (more than three) genes to clarify a new dominant/recessive expression mechanism through studies on expression of S-locus protein 11 genes (SP11), encoding a male S determinant of self-incompatibility in Brassica.  After dominant and recessive gene structures of SP11 were compared, inverted repeat sequences were found in flanking regions of dominant SP11 alleles.  These sequences are highly homologous with promoter regions of recessive SP11 alleles, showed that low molecular weight RNA (small RNA, sRNA) was specifically expressed in the anther tapetum same as SP11.  This siRNA induced DNA methylation in homologous regions of recessive SP11 alleles, and epigenetic controlled gene expressions.

 The achievement was produced through a joint research by Professor Seiji Takayama at Graduate School of Biological Sciences, Nara Institute of Science and Technology and Professor Masao Watanabe at Graduate School of Life Sciences, Tohoku University.

 More than 100 years have passed since Mendel presented Laws of Heredity, and it is still possible to present and introduce new concepts into breed improvements by using the new molecular mechanism to control gene expressions.

 The research results have been published in Nature on August 18, 2010 (http://www.nature.com/nature/index.html).  The paper’s title is “Trans-acting small RNA determines dominance relationships in Brassica self-incompatibility.”

[Contact]
Professor Masao Watanabe
Graduate School of Life Sciences, Tohoku University
TEL: +81-22-217-5681, FAX: +81-2-217-5683
E-mail: nabe*ige.tohoku.ac.jp (Replace * with @)