The complete nucleotide sequences of the double-stranded RNA segments S1, S4, S6, S7 and S12 of the genome of a Rice gall dwarf virus (RGDV) isolate from Thailand were determined. The segments consisted of 4505, 2622, 1648, 1652 and 853 nucleotides, encoding putative proteins of 1458, 725, 489, 511 and 206 amino acids with molecular masses of approximately 166, 80, 53, 59 and 24 kDa, respectively. Homology searches indicated that each of the putative proteins has a counterpart in isolates of Rice dwarf virus (RDV) and Wound tumor virus, two other species in the genus Phytoreovirus. However, no similarities were found to other registered sequences, including those of other viruses that belong to the family Reoviridae. The identities between homologous structural proteins of RGDV and RDV ranged from 34 to 51% and were thus higher than those between homologous non-structural proteins of RGDV and RDV (16-37%). Among the nonstructural proteins, the highest amino acid sequence identity (37%) was observed for RGDV Pns11 and RDV Pns10, a constituent of tubular inclusions. This observation suggests that a specific amino acid backbone might be required for maintaining not only the three-dimensional structure of virions but also that of inclusions. The entire sequence of the RGDV genome is now available.
A pLAFR3 cosmid clone, pVIR6, which contains a virulence gene in the 23-kb insert DNA, was previously constructed. This virulence gene originated from the 52Mdal plasmid of Pseudomonas syringae pv. eriobotryae. Serial deletion analyses of pVIR6 indicated that ca. 7kb of the insert DNA restored pathogenicity to an avirulent PE0 strain, and the deletion plasmid was designated as pKPN35. A 6961-bp insert DNA of pKPN35 was sequenced, and four possible reading frames (ORF1 480bp; ORF2 969bp; ORF3 2193bp; ORF4 516bp) were found in tandem. ORF1 and ORF4 had no significant homology to known genes. ORF2 had an amino acid sequence similar to the transposase of IS5 of E. coli. A recombinant plasmid pNSF1 containing only the ORF3 region restored pathogenicity to the avirulent PE0 strain. However, an ORF3 mutant of pNSF1, which was constructed by deleting a 580-bp BssHII segment from ORF3, failed to restore virulence to the same strain. Consequently, ORF3 was identified as a virulence gene and was named psvA. A HrpL-dependent promoter consensus sequence was found upstream of psvA. The psvA gene product was 731 amino acids long and had a predicted molecular mass of 83.2kDa. The deduced protein of the psvA gene showed no significant similarity to any protein sequence in the data base, although it had some similarity to the N-terminal region of the avrA gene in Pseudomonas syringae pv. glycinea. Production of the deduced protein of the psvA gene was confirmed in E. coli by using the expression vector pET-3a. Southern hybridization analysis indicated that the psvA gene was conserved in P. syringae pathovars myricae and dendropanacis which are causal agents of woody plant galls in Japan.
size. Thus, an understanding the genetic basis underlying the inheritance of embryo size in rice has significant The development of molecular genetic maps has accelerated the implications for quality improvement.identification and mapping of genomic regions controlling quantitative trait loci (QTL) in rice (Oryza sativa L.). Minimizing embryo size in
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