Lack of Correlation between Ammonium Accumulation and Survival of Transgenic Birch Plants with Pine Cytosolic Glutamine Synthetase Gene after “Basta” Herbicide Treatment

Abstract

Transformation of plants with genes encoding a glutamine synthetase (GS), a key nitrogen metabolism enzyme, is usually used to increase productivity. However, overexpression of these genes may increase resistance to phosphinothricin (PPT) that irreversibly inhibits GS causing ammonium accumulation in plant tissues. Transgenic plants of two birch (Betula pubescens) genotypes expressing a pine cytosolic GS gene were used for studying the PPT effect on trees. Two control and 8 transgenic lines were treated with herbicide "Basta" at dose equivalent to 2.5 and 5 Lha −1 . Necrosis and abscission of leaves occurred irrespective of a transgenic status or the treatment dose. Ammonium content in leaf tissue in 3 days after the 5 Lha −1 treatment was substantially increased in all plants, 3.2-16.0 times depending on line. After the 2.5 Lha −1 treatment, ammonium content in three transgenic lines was not different from that in control variant sprayed with water. The herbicide treatment caused more prominent desiccation in the bp3f1 genotype nontransgenic plants as compared to transgenic plants, but not in the bp4a genotype. Lack of correlation between ammonium levels and survival of transgenic plants suggests that ammonium toxicity is not a main reason for the birch plant death after the PPT treatment.

Influence of Nitrogen Availability on Growth of Two Transgenic Birch Species Carrying the Pine GS1a Gene

“…RT-PCR reaction was carried out as previously described [14]. Information about (i) cDNA nucleotide sequences, (ii) location of primers, and (iii) length of amplicons are presented in Figure S1 (for the GS1a gene from P.sylvestris ) and Figure S2 (for the Actin gene from Populus tomentosa ).…”

“…In order to increase productivity of forest plantations the gene of cytosolic GS from Pinus sylvestris was transferred into the genome of Betula [12]. Transgenic plants were tested for growth rate enhancement in the greenhouse [13] and resistance to phosphinothricin treatment [14]. As an extension of the evaluation of these plants, in the present work we estimated the effect of the pine GS1a gene expression on the growth and leaf pigment levels of two birch species ( Betula pubescens and B. pendula ) grown under three different nitrogen levels in outdoor conditions.…”

Genetic Engineering and Genome Editing for Improving Nitrogen Use Efficiency in Plants

“…Transgenic poplar with the GS1 gene was more resistant to PPT in vitro and to herbicide treatment in a growth chamber, but NH 4 + content was not measured [ 218 ]. To assess the PPT resistance, eight transgenic lines belonging to two genotypes of downy birch ( Betula pubescens ) transformed with the pine GS1 gene were treated with Basta herbicide at a dose equivalent to 2.5 and 5 L/ha (half the standard and standard field doses) [ 219 ]. Some lines demonstrated enhanced resistance after low-dose treatment.…”