Water deficiency tolerance of genetically modified common wheat cv. Zymoyarka, containing a heterologous ornithine-δ-aminotransferase gene

Abstract

Aim. To determine water deficiency tolerance of genetically modified common wheat plants (Triticum aestivum L., cv Zymoyarka), containing the heterologous ornithine-δ-aminotransferase gene, based on the analysis of grain productivity and physiological and biochemical characteristics in transgenic and non-transgenic genotypes. Methods. Biochemical spectrophotometric assays: the enzyme ornithine-δ-aminotransferase activity, the free L-proline content, and the photosynthetic pigments content; biotechnological: Agrobacterium-mediated transformation in planta; physiological: morphometric traits and elements of grain productivity; mathematical statistics. Results. It was established that the presence of an additional copy of the ornithine-δ-aminotransferase gene in transgenic plants leads to higher activity of the ornithine-δ- aminotransferase enzyme: by 1.6 times higher on average for all lines as compared to the non-transgenic plants at 70 % of fi eld capacity and by 1.5 – at 30 % fi eld capacity. However, transgenic plants did not differ significantly from the original variety in the free L-proline content either under optimal water conditions or under soil drought. The increase in the total chlorophyll (a + b) content in flag leaves of transgenic plants was established under conditions of both optimal water supply and drought, as compared with the original genotype (increase by 5–7 % and 8–11 %, respectively). The enhanced expression of the orni- thine-δ-aminotransferase gene in the transgenic plants stimulated root growth both under optimal and stressful conditions: the root length of the transformed plants exceeded that of the original variety by 3.4–3.9 cm in the variant with optimal water supply, and by 4.2–4.6 cm – under drought. They were also characterized by a more developed root system. Dry root weight of the transgenic plants exceeded the original variety both in the control (by 23–27 %), and under drought (by 37– 44 %). Under drought, the root dry weight decreased by 29 % in the plants of the original variety, compared 70 % fi eld capacity, and by 11–15 % in the lines. Under 30 % field capacity, the transgenic lines also exceeded non-transformed plants in the number of grains from the whole plant (on average for 3 lines by 26 %) and in the grain weight (by 22 %). Transgenic plants are characterized by the formation of a higher productive shoots number: from 3.2 to 3.4 compared with 2.5 in non-transgenic plants at 70 % fi eld capacity and 2.7–3.1 vs 2.2 at 30 % field capacity it was found. Conclusions. Thus, the analysis of genetically modified common wheat plants cv. Zymoyarka, containing the heterologous alfalfa ornithine-δ- aminotransferase gene, by yield structure elements, morphometric parameters and photosynthetic pigment content showed their better tolerance to soil drought as compared to non-transgenic plants. We explain the improvement of grain productivity of the whole plant in transgenic wheat lines with an additional copy of ornithine-δ-aminotransferase gene by the fact that they have a better developed root system (dry root weight of the transgenic plants exceeded the original variety both in the control by 23–27 %, and under drought by 37–44 %) and a higher (on average for 3 lines – 3.3 compared to 2.5 in non- transgenic plants at 70 % fi eld capacity and 2.9 vs 2.2 at 30 % fi eld capacity) number of productive shoots than in the origi- nal variety both under optimal and insuffi cient water supply.