The de-ubiquitinase UBQUITIN SPECIFIC PROTEASE 15 (UBP15) interacts with the SCF E3 complex adaptor ARABIDOPSIS SKP1 HOMOLOGUE 1 (ASK1) to regulate petal size and fertility in Arabidopsis thaliana.

Ubiquitination is a pivotal type of post-translational modification, which plays a far-reaching role in plant growth and development, as well as in the response of plants to stress. Just like the two sides of a coin, de-ubiquitination also plays an important role in plant life, which has been gradually discovered in recent years. Here, we demonstrate that the UBQUITIN SPECIFIC PROTEASE 15 (UBP15), which is a UBP-type de-ubiquitinase, interacts with the SCF E3 complex adaptor ARABIDOPSIS SKP1 HOMOLOGUE 1 (ASK1) and influences its protein stability to regulate plant fertility and petal size. The UBP15 is associated with the ASK1 physically, as verified by yeast-two-hybrid (Y2H) and protein pull-down in vitro assays. Disruption of ASK1 by a T-DNA insertion generates some abnormal phenotypes, such as low fertility and small petals. Genetic analysis shows that the UBP15 mutation enhances the low-fertility and small-petal phenotypes of ask1 mutant plants. By proteomic analysis, many types of proteins were identified as potential candidate downstream genes associated with the phenotypes of ubp15 ask1 double mutant plants. Taken together, these findings reveal a molecular relationship between ASK1 and UBP15 and their interaction in the regulation of petal size and fertility, which would benefit in-depth research about the ubiquitin-related pathway in plant physiological processes in the future.