A conditional mutation in Arabidopsis thaliana separase induces chromosome non-disjunction, aberrant morphogenesis and cyclin B1;1 stability.
The caspase family protease, separase, is required at anaphase onset to cleave the cohesin complex, which joins sister chromatids. However, among eukaryotes, separases have acquired novel functions. Here, we show that Arabidopsis thaliana radially swollen 4 (rsw4), a temperature-sensitive mutant isolated previously on the basis of root swelling, harbors a mutation in At4g22970, the A. thaliana separase. Loss of separase function in rsw4 at the restrictive temperature is indicated by the widespread failure of replicated chromosomes to disjoin. Surprisingly, rsw4 has neither pronounced cell cycle arrest nor anomalous spindle formation, which occur in other eukaryotes upon loss of separase activity. However, rsw4 roots have disorganized cortical microtubules and accumulate the mitosis-specific cyclin, cyclin B1;1, excessive levels of which have been associated with altered microtubules and morphology. Cyclin B1;1 also accumulates in certain backgrounds in response to DNA damage, but we find no evidence for aberrant responses to DNA damage in rsw4. Our characterization of rsw4 leads us to hypothesize that plant separase, in addition to cleaving cohesin, regulates cyclin B1;1, with profound ramifications for morphogenesis.
Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA.
Shuang
S
Wu
Wolf-Rüdiger
WR
Scheible
Dana
D
Schindelasch
Hilde
H
Van Den Daele
Lieven
L
De Veylder
Tobias I
TI
Baskin
D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D032461:Chromosomes, Plant / Q000235:genetics; D003001:Cloning, Molecular; D019926:Cyclin B / Q000235:genetics / Q000378:metabolism; D010450:Endopeptidases / Q000235:genetics* / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D009024:Morphogenesis / Q000235:genetics*; D009154:Mutation / Q000502:physiology; D009630:Nondisjunction, Genetic / Q000235:genetics*; D018517:Plant Roots / Q000033:anatomy & histology / Q000235:genetics; D030821:Plants, Genetically Modified; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D055550:Protein Stability; D064247:Separase; D013696:Temperature; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D000097722:Cohesins
D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D019926:Cyclin B; D010450:Endopeptidases; D020033:Protein Isoforms; D064247:Separase; D014157:Transcription Factors; D000097722:Cohesins; C508067:BME2 protein, Arabidopsis; C462528:CycB1 protein, Arabidopsis; C577985:AESP protein, Arabidopsis