RFC3 regulates cell proliferation and pathogen resistance in Arabidopsis

Abstract

Replication factor C subunit 3 (RFC3) is one of the small subunits of the RFC complex originally purified from the HeLa cells that is essential for the in vitro replication of Simian virus 40 (SV40). Although RFC has been reported to be involved in DNA replication, DNA repair and check-point control of cell cycle progression in yeast, little is known about the precise function of each subunit of the RFC in plants. We recently reported the identification of rfc3-1, which carries a point mutation leading to plants with enhanced expression of Pathogenesis-Related (PR) genes and resistance against the virulent oomycete Hyaloperonospora arabidopsidis (H. a.) Noco2. The mutant is hypersensitive to SA and has enhanced pathogen resistance independent of Nonexpressor of PR genes 1 (NPR1). The rfc3-1 mutation caused a substitution from a nonpolar aliphatic amino acid (Gly-84) to a negatively charged amino acid (Asp) in functional domain III, which is one of eight conserved domains in the RFC. This may interfere with the interaction between RFC3 and other subunits, compromising the function of the protein complex, and leading to cell proliferation defects in the leaves and roots of Arabidopsis. Furthermore, enhanced expression of PR genes and induction of systemic acquired resistance in rfc3-1 may be caused by a partial loss of RFC function through its involvement in replication-coupled chromatin assembling.

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Acknowledgements

We are grateful for the financial support to Shitou Xia from the National Natural Science Foundation of China and Key Project of Scientific Research from Hunan Provincial Universities and Key Laboratory of Germplasm Innovation and Utilization of Crop.

Figures and Tables

Figure 1 RFC boxes II to VII of RFC proteins from Arabidopsis thaliana and Saccharomyces cerevisiae. Alignment was carried out using ebi ClustalW (www.ebi.ac.uk/clustalw/). The amino acids enclosed in the red frame indicate RFC boxes II to VII, which are amino acid sequence motifs conserved in all RFC subunits. Box VIa is conserved in the large RFC subunits, and box VIb is conserved in the other proteins. The arrow points to the mutation site of AtRFC3 in rfc3-1 mutant.

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