Variation in the inheritance of expression among subclones for unselected (uidA) and selected (bar) transgenes in maize (Zea mays L.)

Abstract

Variation in the inheritance of expression among subclones for an unselected (uidA) and a selected (bar) transgene was analyzed in two individual transformation events in maize. The unselectable gene (uidA) and the selectable gene (bar), on two separate plasmids, were transferred to maize (Hi-II derivative) by particle bombardment of embryogenic calli or suspension cells. A total of 188 fertile T1 plants were obtained from one transformant (transformation event BG which integrated uidA and bar). A total of 98 fertile T1 plants were obtained from a second transformant (transformation event B which integrated bar). Through self-pollination and/or cross-pollination in the greenhouse, approximately 10 000 T2 progeny were obtained from event BG, and more than 1000 T2 progeny were obtained from event B. Segregation of transgene expression was analyzed statistically in a total of 2350 T2 progeny from 40 T1 subclones of event BG and in 217 T2 progeny from six T1 subclones from event B. Variation in the inheritance of expression among subclones for the two transgenes (uidA and bar) was observed in the two transformants. A significant difference was observed between the use of the female or male as the transgenic parent in the inheritance of expression for the two transgenes in event BG. No inheritance through the pollen was observed in two of four T1 subclones analyzed in event B. Co-expression analysis of event BG showed that both transgenes were co-expressed in 67.7% of the T2 plants which expressed at least one of the two transgenes. Of the T2 expressing plants, 30.4% expressed only bar, and 1.9% expressed only uidA. Inactivation of the unselected (uidA) and the selected (bar) transgenes was observed in individual T2 plants.

Expression of a Chimeric Gene Encoding Insecticidal Crystal Protein Cry1Aabc of Bacillus thuringiensis in Chickpea (Cicer arietinum L.) Confers Resistance to Gram Pod Borer (Helicoverpa armigera Hubner.)

“…transgenic wheat ( Srivastava et al, 1996 ), cotton ( Sachs et al, 1998 ), rice ( Datta et al, 1990 ; Pemg et al, 1995 ), and soybean ( Christou et al, 1989 ). The distorted segregation pattern may be due to reduced viability of pollen affecting fertilization ability ( Christou et al, 1989 ; Zhang et al, 1996 ), transgene inactivation ( Spencer et al, 1992 ; Walters et al, 1992 ), recessive lethal gene action ( Scott et al, 1998 ) or other intra genomic conflicts. Our study on pollen viability and germination of transgenic chickpea lines indicate no discernable difference as compared to non-transgenic control chickpea line (unpublished data).…”

Heterologous Acidothermus cellulolyticus 1,4-β-endoglucanase E1 produced within the corn biomass converts corn stover into glucose

“…Plantlets were transferred further to rooting medium containing 2.0 mg/L bialaphos selectable herbicide (33), and maintained for 2-4 wk under the aforementioned light conditions. All cultures were maintained in the dark up to this point.…”

“…T 1 seeds were germinated in vitro on 2.0 mg/L bialaphos selection medium (33) to determine segregation ratios of the offspring. In some cases, transgenic ears were pollinated with wild-type pollen because of lack of sufficient transgenic pollen.…”

Introgressing cry1Ac for Pod Borer Resistance in Chickpea Through Marker-Assisted Backcross Breeding

“…The distorted segregation ratios were detected in BC 1 F 1 and BC 1 F 2 populations developed from Cross A. The distorted ratios generally arise due to transgene inactivation ( Matzke and Matzke 1995 ), low viability/fertilization ability of transgenic pollen ( Zhang et al, 1996 ), reduced germination ( Sachs et al, 1998 ), genetic background ( Scott et al, 1998 ; Wu et al, 2002 ), recessive lethal ( Scott et al, 1998 ) etc. In the present study, segregation distortion in BC 1 F 1 and BC 1 F 2 populations might be a result of reduced germination and not due to 1) transgene inactivation: as cry1Ac amplicon was observed in 46 plants from a total of 130 BC 1 F 1 plants, and 16 out of 190 BC 1 F 2 plants 2) low viability/fertility of transgenic pollen: as the pollen from recipient parent PBG7 (and not from the transgenic line) was used to pollinate F 1 plants to obtain BC 1 F 1 plants; and further both BC 1 F 1 and BC 1 F 2 populations had resulted from a cross between desi PBG7 and desi BS 100B.…”