Revisiting the roles and evolutionary history of Kelch-domain protein phosphatases in plants

GUSTAVO A. MASELLI; JAVIER I. BIANCHI; CLAUDIO H. SLAMOVITS; JOSEP VILARRASA-BLASI; ANA I. CAÑO-DELGADO ; SANTIAGO MORA-GARCIA

Barcelona

Congreso; 1st International Brassinosteroid Conference; 2012

Kelch-domain BSL phosphatases are conserved plant- and alveolate-specific proteins with still poorly characterized functions. BSLs have been described as positive effectors of brassinosteroid (BR) signaling in plants; however, most of the evidence supporting this model has been gathered using BSU1, one of the four homologs codified by Arabidopsis. We reappraised the roles of the remaining three genes, BSL1 to 3. Based on functional, genetic and phylogenetic analyses we show that all three account for the bulk of BSL-related activity and perform an essential role in Arabidopsis that BSU1 is unable to supplement. BSL1, 2 and 3-type sequences are highly conserved and bear an ancient evolutionary history in land plants, whereas BSU-type genes are exclusively found in the Brassicaceae family and have recently been subject to a relaxed selective regime. Simultaneous loss of function of BSL2 and BSL3 produced a novel array of phenotypic alterations, with prevalent organ fusions and vascular disarray, but its effects on BR signaling, albeit detectable, were ambiguous. Our results do not dismiss that these phosphatases may participate to some extent in BR signaling; however, we claim that their roles and, by extension, the current model of BR signal transduction built upon them should be carefully re-evaluated.