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Abstract Rad51 paralogs belong to the Rad52 epistasis group of proteins and are involved in homologous recombination (HR), especially the assembly and stabilization of Rad51, which is a homolog of RecA in eukaryotes. We previously cloned and characterized two RAD51 paralogous genes in Arabidopsis, named AtRAD51C and AtXRCC3, which are considered the counterparts of human RAD51C and XRCC3, respectively. Here we describe the identification of RAD51B homologue in Arabidopsis, AtRAD51B. We found a higher expression of AtRAD51B in flower buds and roots. Expression of AtRAD51B was induced by genotoxic stresses such as ionizing irradiation and treatment with a cross-linking reagent, cisplatin. Yeast two-hybrid analysis showed that AtRad51B interacted with AtRad51C. We also found and characterized T-DNA insertion mutant lines. The mutant lines were devoid of AtRAD51B expression, viable and fertile. The mutants were moderately sensitive to ?-ray and hypersensitive to cisplatin. Our results suggest that AtRAD51B gene product is involved in the repair of double-strand DNA breaks (DSBs) via HR [ABSTRACT FROM AUTHOR]

Two isoforms of starch branching enzyme (Q-enzyme), QEI and QEII, have been purified to homogeneity from developing rice endosperm. QEI and QEII, with molecular weights of about 80 and 85 kDa, respectively, could be fully separated by anion-exchange or hydrophobic chromatography. The peptide maps obtained after V8 proteinase digestion were quite different between the two enzymes. Antibodies prepared against QEI showed no immunological cross-reaction with the QEII protein in Western blot experiments, and anti-QEII serum did not react with the QEI protein. The data indicate that QEI and QEII are distinct proteins encoded by different genes in rice plants. [ABSTRACT FROM AUTHOR]