Anomalias en los comienzos de la transgenesis vegetal: intereses e interpretaciones en torno a las primeras plantas transgenicas / Anomalies in the early stages of plant transgenesis: interests and interpretations surrounding the first transgenic plants

Se presentan los orígenes de la transgénesis vegetal, analizando los experimentos que llevaron a la obtención de las primeras plantas transgénicas. Aquí se entrecruzan actores, prácticas e intereses que resultan emblemáticos de la biotecnología. Se trata, además, de un caso donde se pone en juego el consenso sobre el sentido de experimentos fundamentales. Estos sucesos permiten ilustrar parte de los conflictos en los que se involucran los organismos genéticamente modificados, pues en torno a estos primeros experimentos los científicos articularán representaciones distintas sobre la transgénesis vegetal, valorando de un modo distinto las anomalías que presentaban los primeros experimentos. De este modo, se analizan los intereses e interpretaciones en torno a los primeros experimentos con plantas transgénicas.

The origins of plant transgenesis are discussed and the experiments that led to the first transgenic plants are analyzed. This process involved a series of actors, practices and interests specific to biotechnology. Consensus about the meaning of fundamental experiments was also at issue here. These events illustrate some of the conflicts related to genetically modified organisms, since scientists had different responses to plant transgenesis at the time of the first experiments, and opinions of the anomalies in those experiments varied. Thus, this article analyzes the interests and interpretations surrounding the first experiments involving transgenic plants.

A conserved dibasic site is essential for correct processing of the peptide hormone AtRALF1 in Arabidopsis thaliana.

Prohormone proteins in animals and yeast are typically processed at dibasic sites by convertases. Propeptide hormones are also found in plants but little is known about processing. We show for the first time that a dibasic site upstream of a plant peptide hormone, AtRALF1, is essential for processing. Overexpression of preproAtRALF1 causes semi-dwarfism whereas overexpression of preproAtRALF1(R69A), the propeptide with a mutation in the dibasic site, shows a normal phenotype. RALF1(R69A) plants accumulate only the mutated proprotein and not the processed peptide. In vitro processing using microsomal fractions suggests that processing is carried out by a kexin-like convertase.

Sugarcane (Saccharum spp.).

We describe the procedures for recovering transgenic sugarcane from co-cultivation of both calli and in vitro plants with Agrobacterium tumefaciens. The correct tissue culture strategies and the use of super-binary vector or super-virulent strain are crucial for the successful sugarcane transformation. Both plant regeneration via calli culture and micropropagation strategies can be optimized to a wide spectrum of sugarcane genotypes, thus the procedures presented here could be applied to genetic engineering of Saccharum spp. after minor modifications. For the case of sugarcane transformation using in vitro plants, four selective micropropagation steps must be sufficient to eliminate chimera plants.

Expression of a peroxisome proliferator-activated receptor gene (xPPARalpha) from Xenopus laevis in tobacco (Nicotiana tabacum) plants.

In this work, we have genetically transformed tobacco (Nicotiana tabacum) plants with the peroxisome proliferator-activated receptor cDNA (xPPARalpha) from Xenopus laevis, which is a transcriptional factor involved in the peroxisomal proliferation and induction of fatty acid beta-oxidation in animal cells. Several transgenic lines were generated and one representative line (T) from the R2 generation was selected for further studies. Analysis of free fatty acids revealed that unsaturated fatty acids such as C16:2 and C16:3 were deficient in line T, whereas saturated fatty acids like C16:0, C18:0, and C20:0 were more abundant than in non-transformed plants. Acyl-CoA oxidase (ACOX) activity was assayed as a marker enzyme of beta-oxidation in crude leaf extracts and it was found that in line T there was a threefold increase in enzyme activity. We also found that the peroxisome population was increased and that catalase (CAT) activity was induced by clofibrate, a known activator of xPPARalpha protein, in leaves from line T. Taken together, these findings suggest that xPPARalpha is functional in plants and that its expression in tobacco leads to changes in general lipid metabolism and peroxisomal proliferation as reported in animal cells. Furthermore, it indicates that there is an endogenous ligand in tobacco cells able to activate xPPARalpha.