Novel Plant-specific Cyclin-dependent Kinase Inhibitors Induced by Biotic and Abiotic Stresses

Adrian Peres,Michelle L Churchman,Srivaidehirani Hariharan,Kristiina Himanen,Aurine Verkest,Klaas Vandepoele,Zoltan Magyar,Yves Hatzfeld,Els Van Der Schueren,Gerrit T.S Beemster,Valerie Frankard,John C Larkin,Dirk Inzé,Lieven De Veylder

doi:10.1074/jbc.m703326200

Abstract

The EL2 gene of rice (Oryza sativa), previously classified as early response gene against the potent biotic elicitor N-acetylchitoheptaose and encoding a short polypeptide with unknown function, was identified as a novel cell cycle regulatory gene related to the recently reported SIAMESE (SIM) gene of Arabidopsis thaliana. Iterative two-hybrid screens, in vitro pull-down assays, and fluorescence resonance energy transfer analyses showed that Orysa; EL2 binds the cyclin-dependent kinase (CDK) CDKA1;1 and D-type cyclins. No interaction was observed with the plant-specific B-type CDKs. The amino acid motif ELERFL was identified to be essential for cyclin, but not for CDK binding. Orysa;EL2 impaired the ability of Orysa; CYCD5;3 to complement a budding yeast (Saccharomyces cerevisiae) triple CLN mutant, whereas recombinant protein inhibited CDK activity in vitro. Moreover, Orysa;EL2 was able to rescue the multicellular trichome phenotype of sim mutants of Arabidopsis, unequivocally demonstrating that Orysa;EL2 operates as a cell cycle inhibitor. Orysa;EL2 mRNA levels were induced by cold, drought, and propionic acid. Our data suggest that Orysa;EL2 encodes a new type of plant CDK inhibitor that links cell cycle progression with biotic and abiotic stress responses.

Highlights

The model plant species Arabidopsis thaliana counts up to 12 cyclin-dependent kinase (CDK) and 49 cyclins that have been grouped into different types according to sequence similarity [2, 3]
Only one class of plant CDK inhibitors (CKIs) has been described whose members were designated as Kip-related proteins (KRPs), because of their similarity with the mammalian Kip/Cip proteins, but some members are known as Interactors of Cdc2 Kinases (ICKs) [21]
The EIEDFF domain resides into the mapped cyclinbinding domain of KRPs [37]

Summary

Introduction

The model plant species Arabidopsis thaliana counts up to 12 CDKs and 49 cyclins that have been grouped into different types according to sequence similarity [2, 3]. The plant-specific B-type CDKs hold a divergent cyclin-binding domain and control the G2-to-M transition only [1]. SIM interacts with A-type CDKs and D-type cyclins, and its overproduction results into a strong inhibition of cell division activity.

Results

Conclusion