Specific domain structures control abscisic acid-, salicylic acid-, and stress-mediated SIZ1 phenotypes.
SIZ1 (for yeast SAP and MIZ1) encodes the sole ortholog of mammalian PIAS (for protein inhibitor of activated STAT) and yeast SIZ SUMO (for small ubiquitin-related modifier) E3 ligases in Arabidopsis (Arabidopsis thaliana). Four conserved motifs in SIZ1 include SAP (for scaffold attachment factor A/B/acinus/PIAS domain), PINIT (for proline-isoleucine-asparagine-isoleucine-threonine), SP-RING (for SIZ/PIAS-RING), and SXS (for serine-X-serine, where X is any amino acid) motifs. SIZ1 contains, in addition, a PHD (for plant homeodomain) typical of plant PIAS proteins. We determined phenotypes of siz1-2 knockout mutants transformed with SIZ1 alleles carrying point mutations in the predicted domains. Domain SP-RING is required for SUMO conjugation activity and nuclear localization of SIZ1. Salicylic acid (SA) accumulation and SA-dependent phenotypes of siz1-2, such as diminished plant size, heightened innate immunity, and abscisic acid inhibition of cotyledon greening, as well as SA-independent basal thermotolerance were not complemented by the altered SP-RING allele of SIZ1. The SXS domain also controlled SA accumulation and was involved in greening and expansion of cotyledons of seedlings germinated in the presence of abscisic acid. Mutations of the PHD zinc finger domain and the PINIT motif affected in vivo SUMOylation. Expression of the PHD and/or PINIT domain mutant alleles of SIZ1 in siz1-2 promoted hypocotyl elongation in response to sugar and light. The various domains of SIZ1 make unique contributions to the plant's ability to cope with its environment.
Cheong
Mi Sun
MS
Division of Applied Life Science (Brain Korea 21 Program), PMBBRC, EB-NCRC, Gyeongsang National University, Jinju City 660-701, Korea.
Park
Hyeong Cheol
HC
Hong
Mi Ju
MJ
Lee
Jiyoung
J
Choi
Wonkyun
W
Jin
Jing Bo
JB
Bohnert
Hans J
HJ
Lee
Sang Yeol
SY
Bressan
Ray A
RA
Yun
Dae-Jin
DJ
D000040:Abscisic Acid / Q000494:pharmacology*; D000222:Adaptation, Physiological / Q000187:drug effects / Q000528:radiation effects; D017360:Arabidopsis / Q000187:drug effects* / Q000201:enzymology* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism*; D002241:Carbohydrates / Q000494:pharmacology; D018548:Cotyledon / Q000187:drug effects / Q000201:enzymology / Q000528:radiation effects; D005816:Genetic Complementation Test; D018525:Germination / Q000187:drug effects / Q000528:radiation effects; D018869:Heat-Shock Response / Q000187:drug effects / Q000528:radiation effects; D018546:Hypocotyl / Q000033:anatomy & histology / Q000187:drug effects / Q000201:enzymology / Q000528:radiation effects; D008025:Ligases / Q000737:chemistry* / Q000378:metabolism*; D008027:Light; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D018515:Plant Leaves / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D017434:Protein Structure, Tertiary; D020156:Salicylic Acid / Q000494:pharmacology*; D013312:Stress, Physiological / Q000187:drug effects* / Q000528:radiation effects; D013329:Structure-Activity Relationship; D013696:Temperature; D014170:Transformation, Genetic / Q000187:drug effects / Q000528:radiation effects
D029681:Arabidopsis Proteins; D002241:Carbohydrates; D000040:Abscisic Acid; D008025:Ligases; C502552:SIZ1 protein, Arabidopsis; D020156:Salicylic Acid