Isolation and characterization of an ipt gene from the Ti plasmid Bo542

Summary A 1.9 kb clone of the T-DNA region of the Agrobacterium tumefaciens Ti plasmid Bo542 which exhibited homology to the isopentenyl transferase (ipt) locus of pTiA6 was identified by low stringency DNA hybridization. Introduction of this segment of pTiBo542 DNA into cells of Nicotiana tabacum or N. glauca caused tumor formation in vivo, and allowed hormone independent growth in vitro. Furthermore, this DNA segment complemented ipt mutant strains of A. tumefaciens, restoring their ability to cause tumors on Kalanchöe leaves and tomato stems. The complete DNA sequence of this segment has been determined, revealing an open reading frame homologous to other known Agrobacterium ipt genes.     

Ecotype-Specific Expression of a Flowering Mutant Phenotype in Arabidopsis thaliana

The majority of mutations that delay flowering in Arabidopsis thaliana have been identified in studies of the Landsberg erecta (Ler) ecotype. In this report we describe a gene (referred to as FLD) that, when mutated, delays flowering in the Columbia ecotype but has a minimal phenotype in the Ler genetic background. The late-flowering phenotype of fld mutants requires a non-Ler allele of another gene involved in the control of flowering time, Flowering Locus C. fld mutants retain a photoperiod response, and the flowering time of fld mutants can be reduced by cold treatment and low red/far-red light ratios.     

Population genetics and phylogenetics of DNA sequence variation at multiple loci within the Drosophila melanogaster species complex

Two regions of the genome, a 1-kbp portion of the zeste locus and a 1.1- kbp portion of the yolk protein 2 locus, were sequenced in six individuals from each of four species: Drosophila melanogaster, D. simulans, D. mauritiana, and D. sechellia. The species and strains were the same as those of a previous study of a 1.9-kbp region of the period locus. No evidence was found for recent balancing or directional selection or for the accumulation of selected differences between species. Yolk protein 2 has a high level of amino acid replacement variation and a low level of synonymous variation, while zeste has the opposite pattern. This contrast is consistent with information on gene function and patterns of codon bias. Polymorphism levels are consistent with a ranking of effective population sizes, from low to high, in the following order: D. sechellia, D. melanogaster, D.mauritiana, and D. simulans. The apparent species relationships are very similar to those suggested by the period locus study. In particular, D. simulans appears to be a large population that is still segregating variation that arose before the separation of D. mauritiana and D. sechellia. It is estimated that the separation of ancestral D. melanogaster from the other species occurred 2.5-3.4 Mya. The separations of D. sechellia and D. mauritiana from ancestral D. simulans appear to have occurred 0.58- 0.86 Mya, with D. mauritiana having diverged from ancestral D. simulans 0.1 Myr more recently than D. sechellia.      

Characterization of a stress-induced,developmentally regulated gene family from soybean

We describe a family of stress-induced, developmentally regulated soybean genes for which cDNAs have been obtained from two different cultivars (Glycine max cv. Mandarin and Glycine max cv. Williams). The mRNAs corresponding to these cDNAs, called SAM22 and H4, respectively, accumulate predominantly in the roots of soybean seedlings but are present at high levels in the roots and leaves of mature plants. SAM22 accumulation is especially dramatic in senescent leaves. In addition, SAM22 accumulation can be induced in young leaves by wounding or by transpiration-mediated uptake of salicylic acid, methyl viologen, fungal elicitor, hydrogen peroxide or sodium phosphate (pH 6.9). Taken together, these data indicate that the genes corresponding to SAM22 and H4 are induced by various stresses and developmental cues. Southern blot analysis indicates that multiple copies of sequences related to SAM22 exist in the soybean genome. We also show that the nucleotide sequences of the cDNAs corresponding to SAM22 and H4 are 86% identical at the nucleotide level to each other and 70% identical at the amino acid level to the disease resistance response proteins of Pisum sativum.     

Digital image analysis of AgNORs in cervical smears of women with premalignant and malignant lesions of the uterine cervix

We performed a hospital-based, unmatched case-control study to investigate the association between progressive stages of cervical neoplasia and digital analysis of cell proliferation by silver stained nucleolus organizer region associated proteins (AgNORs). We measured cell proliferation levels in the cervical epithelial cells of 10 women with low grade squamous intraepithelial lesions (LG-SIL), eight with high grade squamous intraepithelial lesions (HG-SIL), 11 with cervical cancer (CC) and eight with no cervical lesions (controls) using the AgNORs technique. Cell proliferation was measured by digital image analysis (DIA). DIA revealed increased total areas of AgNORs in HG-SIL and CC compared to LG-SIL and control patients. AgNORs with a kidney or cluster shape exhibited greater areas than those with a spherical or long shape. We propose a cut-off of 118 pixels to differentiate benign (control and LG-SIL) from malignant (HG-SIL and CC) lesions. DIA of AgNORs is a simple and inexpensive method for studying proliferation. The increased total area of AgNORs in malignant lesions provides information regarding cell behavior and may be related to cervical carcinogenesis; however, further validation studies are required to establish its usefulness in cytological analysis.