Group Leader: L. Maria Lois (CSIC Assistant Professor)
Postdoctoral Researchers: Silvia Manrique (until January 13), Maria Guirola (since March 2013 until October 2013), Arnaldo Luis Schapire (since June 2013)
PhD Students: Laura Castaño, Abraham Mas, Inês Teixeira (until May 2013)
Undergrad or Master Students: Arnau Rovira (since January 2012 until February 2013), Gaelle La Verde (since March 2012 until June 2012).
General Research Support: Natalia Rodrigo (until April 2012), Cristina Cañadas (since July 2012)
Following previous reports focused on the analysis of different components of the SUMO conjugation machinery in plants (Chosed et al. 2006, Castaño-Miquel et al. 2011), we have studied the intriguing higher complexity of the E1 activating enzyme in plants when compared to yeast and animals. In Arabidopsis, the E1 small subunit is duplicated in two isoforms, AtSAE1a and AtSAE1b, which affect the SUMO conjugation rate, pointing to a rate limiting role of SUMO activation during the conjugation cascade. E1 diversification is not restricted to Arabidopsis and it remains to be elucidated whether other regulatory mechanisms, such as SAE1 posttranslational modifications, may contribute to bring functional diversity to other systems having a single E1 isoform (Castaño-Miquel et al., 2013). Our findings point to a crucial role of the E1 activating enzyme by conferring SUMO paralog specificity and modulating conjugation rate.
We have also put major effort into the dissection of SUMO role during seed development. Genetic studies determined that SUMO is essential during early stages of seed development and these mutations are recessive (Saracco et al., 2007). We speculated that SUMO may mediate ABA signaling later, during seed maturation, when seeds enter into a dehydration phase and dormancy is generated. Events occurring during this phase are also critical for producing high-quality seeds, which are characterized by the capacity for synchronous germination and rapid establishment of vigorous and uniform seedlings even under varying levels of abiotic stress. High seed quality also display better resistance against pathogen development (Rajjou et al., 2012). In order to get new insights into the molecular mechanisms controlling seed development, we have characterize SUMO conjugation dynamics, performed epigenetic analysis between SUMO and ABA, and identified SUMO conjugates in seeds. We have established the existence of a SUMO conjugate pattern specific to very early stages of embryo development that is replaced by a pattern specific to mature seeds. Considering the dramatic qualitative and quantitative change in SUMO conjugates, we extended our characterization to the first stages of germination. Our results indicated that the mature seed SUMO conjugation pattern was rapidly replaced by a vegetative pattern within two days after exposure to germination conditions. In addition, siz1 SUMO E3 ligase mutant plants display increased dormancy and confer lethality to ABA-related mutant plants, such as gin1-3 and abi3-8, pointing to the existence of a cross-talk between ABA and SUMO also in seed development (manuscript in preparation).
- Analysis of the molecular mechanisms controlling SUMO conjugation in vivo.
- Identification of the molecular effectors that mediate SUMO biological role: identification of SUMO targets and SUMO interacting proteins.
- Regulation of seed development by SUMO.
- Development of SUMO conjugation inhibitors.
Perez-Gil J., Uros E.M., Sauret-Gueto S., Lois L.M., Kirby J., Nishimoto M., Baidoo E.E.K., Keasling J.D., Boronat A., Rodriguez-Concepcion M.
Mutations in Escherichia coli aceE and ribB genes allow survival of strains defective in the first step of the isoprenoid biosynthesis pathway
(2012) PLoS ONE, vol. 7 (8), Art. number e43775
Castano-Miquel L., Segui J., Manrique S., Teixeira I., Carretero-Paulet L., Atencio F., Lois L.M.
Diversification of SUMO-activating enzyme in arabidopsis: Implications in SUMO conjugation
(2013) Molecular Plant, vol. 6 (5), pp. 1646-1660