Regeneration of glyphosate-tolerant Nicotiana tabacum after plastid transformation with a mutated variant of bacterial aroA gene

Presence of antibiotic resistance markers has always been considered as one of the main safety concerns in transgenic plants and their derived products. Elimination of antibiotic selectable markers from transgenics is a major hurdle for finding efficient and safe candidates. Herbicide tolerance genes might be attractive alternatives. In this study, a variant form of the 5-enoylpyruvyl shikimate-3-phosphate synthase [EPSPS] gene that harbors glycine at position 96 to alanine and alanine 183 to threonine substitutions and confers higher resistance to the broad-spectrum herbicide, glyphosate, was substituted against the spectinomycin resistant gene as a sole selectable marker for plastid transformation of Nicotiana tabacum. Plastid transformation was carried out using the biolistic delivery procedure while delivery parameters such as rupture disk pressure, bombardment distance, etc had been optimized first. A previous study showed that the glyphosate herbicide imposes lethal effects on the structure and integrity of the plastid membrane, even at low concentrations. In order to overcome this problem, a modified procedure for selection of transplastomic cells was used. A long preculture incubation period followed by a gradual increased in glyphosate concentration led to sufficient expression of the transgene. Tolerant calli were thus regenerated through direct selection of transformed plastids in the presence of the glyphosate

Transient expression of human growth hormone in potato [Solanum tuberosum], tobacco [Nicotiana tobacum] and lettuce [Lactuca sativa] leaves by agroinfiltration

The use of polymorphic markers in breeding programmes could make selection more accurate and efficient. A total of 324 individuals from six Iranian cattle populations [Sarabi, Golpayegani, Sistani, Taleshi, Mazandarani, Dashtiyari], F1 Golpayegani Brown Swiss and Iranian buffalo populations were genotyped for the Pit-1 HinfI and leptin Sau3AI polymorphisms by the polymerase chain reaction and restriction fragment length polymorphism [PCR-RFLP]. The genotype and gene frequencies for each breed were determined and shown to be quite variable among the breeds. The highest frequencies of allele B for the leptin gene and allele A for the Pit-1 gene were found in Dashtiyari and Sistani cattle, respectively. According to our results, the highest AB genotype frequencies were found in the Taleshi and F1 Golpayegani x Brown Swiss cross for the leptin and Pit-1 genes, respectively. These allele frequencies were comparable to previously published data on exotic breeds. The highest and lowest heterozygosities were found in Taleshi and Dashtiyari cattle for the leptin gene and in F1 Golpayegani x Brown Swiss cross and Sistani cattle for the Pit-1 gene, respectively. These values indicated the presence of low variation for these genes in the studied populations. The possible association between molecular polymorphisms within these candidate genes and economic traits for the studied populations should be further investigated