Little is presently known about the nuclear-encoded genes for cytochrome c oxidase (COX) in higher plants. In rice, only the nuclear-encoded COX5b gene has been reported. To understand the relationship between the expression of nuclear-encoded and mitochondrial-encoded COX genes in rice, we first characterized a cDNA encoding one of the other nuclear COX genes, COX5c, which encodes 63 amino acids. The deduced amino acid sequence of COX5c from rice was highly homologous to that from sweet potato. Genomic Southern hybridization indicated that the rice COX5c subunit is encoded by a single copy of the COX5c gene. Furthermore, we compared the expression patterns of the nuclear-encoded COX5c and COX5b genes with the expression pattern of the mitochondrial-encoded COX1 gene among several organs by Northern blot analysis. The results suggested that regulatory systems of expression between the nuclear-encoded and the mitochondrial-encoded COX genes are different among different organs in rice.

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Homoeologous relationships between Haynaldia villosa chromosomes and bread wheat (Triticum aestivum) were studied in two sets of wheat-H. villosa addition lines and five substitution lines by restriction fragment length polymorphism (RFLP) analysis. H. villosa chromosomes 1V to 7V are homoeologous with group 1 to 7 chromosomes of wheat. In wheat-H. villosa substitution lines, the wheat chromosomes 3D, 4D, 5D, and 6A were replaced by homoeologous H. villosa chromosomes. The addition lines for chromosome 4V and 5V from three different accessions were analyzed by C-banding, and characterized by RFLP markers. Group 4 and 5 translocations were detected on chromosomes 4V#1 and 5V#1 (produced by Sears, unpublished), and 4V#3 and 5V#3 (produced by Lukaszewski, personal communication). The translocation breakpoints were located between Xpsr1051 and Xpsr115 on 4VL and between Xpsr370 and Xcdo1312 on 5VL. The similarities of the breakpoints within the Triticeae indicates that the specific chromosome regions of the homoeologous groups 4 and 5 are "hot spots" for chromosome breaks. The group-5 homoeologous loci, Xpsr115, Xpsr580, and Xcdo484, also were detected on the chromosome 4V#2 (produced by Liu et al., 1988) with a similar breakpoint between Xpsr1051 and Xpsr115. However, no reciprocal translocation was detected on the chromosome 5V#2. Possible reasons for difference of 4/5 translocation in this species are discussed.

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The 441-bp DNA segment in a PCR-amplified fragment from Oryza sativa cv. IR36 was found to have a sequence with features characteristic of LTRs of retroelements, which was named RIRE2 (Rice retroelement #2) and further analyzed. Cloning and sequencing analyses of the DNA segments connected to LTR-like sequence showed that RIRE2 has a long internal region almost 10 kb long that is flanked by LTR-like sequences. This internal region carries a primer binding site (PBS) and polypurine tract (PPT) which are necessary for cDNA synthesis of retroelements. The PBS sequence is complementary to the 3' end region of tRNA^Arg. The internal region has an rt gene homologous to that of gypsy-type retrotransposons, evidence that RIRE2 is indeed a retrotransposon related to gypsy from Drosophila. RIRE2 has an extra sequence more than 4 kb long in the region downstream of gag-pol. Phylogenetic analysis of the putative amino-acid sequences of the rt gene as well as the int gene showed that RIRE2 is related to a group of gypsy-type retrotransposons of a large size that include Grande1-4 of teosinte, Tat4-1 and Athila1-1 of Arabidopsis thaliana, and Cyclops-2 of pea, but distantly related to any other group of gypsy-type retrotransposons, including RIRE3 and RIRE8 of rice. RIRE2 and Grande1-4 had the highest homology in the gag-pol region, but the nucleotide sequences of the LTR regions differed. Both elements had significant homology in the middle area of the extra regions downstream of gag-pol, in which they had an open reading frame encoding a protein with no known function on the opposite strand from that coding for gag-pol.

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Variation and genetic control of seed protein in foxtail millet (Setaria italica) were studied using SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Variation in the electrophoregram of the total seed protein were detected in the range between 20 and 30 kDa which is derived from the polymorphism of five prolamin bands. The segregation for each of the bands in F₂ seeds showed that these bands are governed by seven alleles at two loci, Pro1 and Pro2, which are not linked to one another. Among 271 local cultivars examined, eight out of ten possible genotypes were observed. With its level of diversity comparable to that of isozymes, the alleles conferring prolamin polymorphism are useful genetic markers.

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Hordatines A and B, strong antifungal components in shoots of barley seedlings, were found to occur in a barley chromosome 2H addition line to wheat, but not in a wheat line carrying the long arm of chromosome 2H. These results showed that some genes that encode hordatine biosynthetic enzymes are located on the short arm of chromosome 2H. The total content of the hordatines was about six fold less than that in the parental barley, but was still at a concentration more than 20-fold higher than that required for inhibition of spore germination of pathogenic fungi.

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The flhD and flhC genes constitute the flagellar master operon whose products are required for expression of all the remaining flagellar operons in Salmonella typhimurium. Here we report the molecular structure and in vivo and in vitro expression of the flhD operon. Nucleotide sequence analysis revealed that the upstream region of this operon contains the consensus sequence for the cAMP-CRP binding site. Primer extension analysis demonstrated six possible transcription start sites for this operon. They include CRP-dependent and CRP-repressible transcription start sites. The CRP-dependent transcription start site is located 203 bp upstream of the initiation codon of the flhD gene and preceded by the consensus sequences of the -10 and -35 regions of the σ⁷⁰-dependent promoter. The putative cAMP-CRP binding site is located centered 70 bp upstream of this start site. The CRP-repressible transcription start site is located within this putative cAMP-CRP binding site. These two start sites were confirmed by in vitro transcription experiments using σ⁷⁰-RNA polymerase with or without cAMP-CRP.

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Flagellar class 3 operons of Escherichia coli and Salmonella are transcribed by RNA polymerase containing σ²⁸. The consensus sequence of the σ²⁸-dependent pro-moters was believed to be TAAA N15 GCCGATAA. In this study, we found that the E. coli genome contains a large number of sequences homologous to this consen-sus. However, we showed that they do not always exert a σ²⁸-dependent promoter activity. We compare more carefully the sequences of the class 3 flagellar promot-ers and propose a revised structure of the σ²⁸-dependent promoters as TAAAGTTT N11 GCCGATAA.

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