UBIQUITIN SPECIFIC PROTEASE 26 is required for seed development and the repression of PHERES1 in Arabidopsis

The Arabidopsis mutant Atubp26 initiates autonomous endosperm at a frequency of about 1% in the absence of fertilization and develops arrested seeds at a frequency of about 65% when self-pollinated. These phenotypes are similar to those of the FERTILIZATION INDEPENDENT SEED (FIS) class mutants, mea, fis2, fie, and Atmsi1 which also show development of the central cell into endosperm in the absence of fertilization and arrest of the embryo following fertilization. Atubp26 results from a T-DNA insertion in the UBIQUITIN SPECIFIC PROTEASE gene AtUBP26 which catalyzes deubiquitination of histone H2B and is required for heterochromatin silencing. The paternal copy of AtUBP26 is able to complement the loss of function of the maternal copy in post-fertilization seed development. This contrasts to the fis class mutants where the paternal FIS copy does not rescue aborted seeds. As in the fis class mutants, the Polycomb Group (PcG) complex target gene, PHERES1 (PHE1) is expressed at higher levels in Atubp26 ovules than in wild type; there is a lower level of H3K27me3 at the PHE1 locus. The phenotypes suggest that AtUBP26 is required for normal seed development and the repression of PHE1.

Key Words: FIS, H2B ubiquitination, Polycomb, Seed development, histone methylation

Online ISS 1091-6490
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