Search

Abstract Background Transgenic trees currently are being produced by Agrobacterium-mediated transformation and biolistics. The future use of transformed trees on a commercial basis depends upon thorough evaluation of the potential environmental and public health risk of the modified plants, transgene stability over a prolonged period of time and the effect of the gene on tree and fruit characteristics. We studied the stability of expression and the effect on resistance to the fire blight disease of the lytic protein gene, attacin E, in the apple cultivar 'Galaxy' grown in the field for 12 years. Results Using Southern and western blot analysis, we compared transgene copy number and observed stability of expression of this gene in the leaves and fruit in several transformed lines during a 12 year period. No silenced transgenic plant was detected. Also the expression of this gene resulted in an increase in resistance to fire blight throughout 12 years of orchard trial and did not affect fruit shape, size, acidity, firmness, weight or sugar level, tree morphology, leaf shape or flower morphology or color compared to the control. Conclusion Overall, these results suggest that transgene expression in perennial species, such as fruit trees, remains stable in time and space, over extended periods and in different organs. This report shows that it is possible to improve a desirable trait in apple, such as the resistance to a pathogen, through genetic engineering, without adverse alteration of fruit characteristics and tree shape.

Background: Transgenic trees currently are being produced by Agrobacterium-mediated transformation and biolistics. The future use of transformed trees on a commercial basis depends upon thorough evaluation of the potential environmental and public health risk of the modified plants, transgene stability over a prolonged period of time and the effect of the gene on tree and fruit characteristics. We studied the stability of expression and the effect on resistance to the fire blight disease of the lytic protein gene, attacin E, in the apple cultivar 'Galaxy' grown in the field for 12 years. Results: Using Southern and western blot analysis, we compared transgene copy number and observed stability of expression of this gene in the leaves and fruit in several transformed lines during a 12 year period. No silenced transgenic plant was detected. Also the expression of this gene resulted in an increase in resistance to fire blight throughout 12 years of orchard trial and did not affect fruit shape, size, acidity, firmness, weight or sugar level, tree morphology, leaf shape or flower morphology or color compared to the control. Conclusion: Overall, these results suggest that transgene expression in perennial species, such as fruit trees, remains stable in time and space, over extended periods and in different organs. This report shows that it is possible to improve a desirable trait in apple, such as the resistance to a pathogen, through genetic engineering, without adverse alteration of fruit characteristics and tree shape. [ABSTRACT FROM AUTHOR]

Malate accumulation in the vacuole largely determines apple ( Malus domestica ) fruit acidity, and low fruit acidity is strongly associated with truncation of Ma1 , an ortholog of ALUMINUM-ACTIVATED MALATE TRANSPORTER9 ( ALMT9 ) in Arabidopsis ( Arabidopsis thaliana ). A mutation at base 1,455 in the open reading frame of Ma1 leads to a premature stop codon that truncates the protein by 84 amino acids at its C-terminal end. Here, we report that both the full-length protein, Ma1, and its naturally occurring truncated protein, ma1, localize to the tonoplast; when expressed in Xenopus laevis oocytes and Nicotiana benthamiana cells, Ma1 mediates a malate-dependent inward-rectifying current, whereas the ma1-mediated transmembrane current is much weaker, indicating that ma1 has significantly lower malate transport activity than Ma1. RNA interference suppression of Ma1 expression in 'McIntosh' apple leaves, 'Empire' apple fruit, and 'Orin' apple calli results in a significant decrease in malate level. Genotyping and phenotyping of 186 apple accessions from a diverse genetic background of 17 Malus species combined with the functional analyses described above indicate that Ma1 plays a key role in determining fruit acidity and that the truncation of Ma1 to ma1 is genetically responsible for low fruit acidity in apple. Furthermore, we identified a C-terminal domain conserved in all tonoplast-localized ALMTs essential for Ma1 function; protein truncations into this conserved domain significantly lower Ma1 transport activity. We conclude that the truncation of Ma1 to ma1 reduces its malate transport function by removing a conserved C-terminal domain, leading to low fruit acidity in apple., (© 2020 American Society of Plant Biologists. All Rights Reserved.)