Premium
Characterization of spa mutants in the moss Physcomitrella provides evidence for functional divergence of SPA genes during the evolution of land plants
Author(s) -
Artz Oliver,
Dickopf Stephen,
Ranjan Aashish,
Kreiss Melanie,
Abraham Elena Theres,
Boll Vanessa,
Rensing Stefan A.,
Hoecker Ute
Publication year - 2019
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.16004
Subject(s) - physcomitrella patens , arabidopsis , mutant , photomorphogenesis , biology , protonema , gene , functional divergence , microbiology and biotechnology , arabidopsis thaliana , repressor , bryopsida , transcription factor , genetics , botany , gene family , gene expression , moss
Summary The Arabidopsis COP 1/ SPA complex is a key repressor of photomorphogenesis that suppresses light signaling in the dark. Both COP 1 and SPA proteins are essential components of this complex. Although COP 1 also exists in humans, SPA genes are specific to the green lineage. To elucidate the evolution of SPA genes we analyzed SPA functions in the moss Physcomitrella patens by characterizing knockout mutants in the two Physcomitrella SPA genes Pp SPA a and Pp SPA b . Light‐grown Ppspa AB double mutants exhibit smaller gametophores than the wild‐type. In the dark, Ppspa AB mutant gametophores show enhanced continuation of growth but etiolate normally. Gravitropism in the dark is reduced in Ppspa AB mutant protonemata. The expression of light‐regulated genes is mostly not constitutive in Ppspa AB mutants. Pp SPA and Pp COP 1 interact; Pp COP 1 also interacts with the transcription factor Pp HY 5 and, indeed, Pp HY 5 is destabilized in dark‐grown Physcomitrella . Degradation of Pp HY 5 in darkness, however, does not require Pp SPA a and Pp SPA b . The data suggest that COP 1/ SPA ‐mediated light signaling is only partially conserved between Arabidopsis and Physcomitrella . Whereas COP 1/ SPA interaction and HY 5 degradation in darkness is conserved, the role of SPA proteins appears to have diverged. Pp SPA genes, unlike their Arabidopsis counterparts, are only required to suppress a subset of light responses in darkness.