Richard F. Barker

Nucleotide sequence of the T-DNA region from theA grobacterium tumefaciens octopine Ti plasmid pTi15955.

The complete nucleotide sequence of the transferred region (T-DNA) of an octopine tumor inducing (Ti) plasmid fromAgrobacterium tumefaciens (pTi15955) has been determined. A total of 24 595 nucleotides extending approximately 900 bases to either side of the outermost, T-DNA boundaries was sequenced. Computer analysis of the sequenced portion of the Ti plasmid revealed that recognition sites for 72 restriction endonucleases are present in the DNA sequence at least once; no site forEcoK exists in this DNA sequence. Two imperfect 24 base repeats border the T-DNA sequence; the left starts at position 909 and the right ends at position 23 782, giving the T-DNA region a total length, of 22 874 nucleotides. Another two similar 24 base repeats lie within T-DNA and divide it, into three distinct domains: T-left (TL-DNA) 13 175 bp of apparently eukaryotic origin; T-center (TC-DNA) 1816 bp of prokaryotic origin; and T-right (TR-DNA) 7 883 bp of eukaryotic origin. The T-DNA contains nine reported transcripts, however, 26 open reading frames longer than 300 bases that start with an ATG initiation codon were found. Fourteen open reading frames are bounded by putative eukaryotic promoters, ribosome binding sites, and poly(A) addition sites and occur only in TL-and TR-DNAs. No open reading frames showing eukaryotic promoter sequences are located within the TC-DNA.

Protein and cDNA sequences of Bowman-Birk protease inhibitors from the cowpea (Vigna unguiculata Walp.)

The protein and gene sequences of the cowpea Bowman-Birk type trypsin inhibitor which confers enhanced insect resistance to transgenic tobacco plants, and of cowpea trypsin/chymotrypsin inhibitors are presented. There are regions of high conservation and high divergence within the 5′ leader, mature protein and 3′ non-coding regions of the Bowman-Birk inhibitors and in the genes which encode them in different members of this family within the Leguminosae. The practical implications of this finding for studies on the evolution of plants and the utilization of these genes for enhancing insect resistance is discussed.

Agroinfection and nucleotide sequence of cloned wheat dwarf virus DNA.

Cloned DNA of the geminivirus wheat dwarf virus (WDV) was successfully used to infect seedling wheat plants. The clone was derived from circular double-stranded viral DNA isolated from naturally infected tissue. The initiation of infection was mediated by Agrobacterium tumefaciens using cloned dimeric WDV genomes in a binary Agrobacterium vector. The WDV DNA which comprised the infectious clone was sequenced and is compared with the published sequence of a Swedish isolate of the same virus. The results confirm that the single WDV genome component of 2.75 kb carries all the information necessary for production of viral symptoms, virus particles and viral double- and single-stranded DNA forms.