This study investigated the impact of constitutively expressed Trichoderma atroviride genes encoding exochitinase nag70 or endochitinase ech42 in transgenic lines of the apple cultivar Pinova on the symbiosis with arbuscular mycorrhizal fungi (AMF). We compared the exo- and endochitinase activities of leaves and roots from non-transgenic Pinova and the transgenic lines T386 and T389. Local and systemic effects were examined using own-rooted trees and trees grafted onto rootstock M9. Scab susceptibility was also assessed in own-rooted and grafted trees. AMF root colonization was assessed microscopically in the roots of apple trees cultivated in pots with artificial substrate and inoculated with the AMF Glomus intraradices and Glomus mosseae. Own-rooted transgenic lines had significantly higher chitinase activities in their leaves and roots compared to non-transgenic Pinova. Both of the own-rooted transgenic lines showed significantly fewer symptoms of scab infection as well as significantly lower root colonization by AMF. Biomass production was significantly reduced in both own-rooted transgenic lines. Rootstock M9 influenced chitinase activities in the leaves of grafted scions. When grafted onto M9, the leaf chitinase activities of non-transgenic Pinova (M9/Pinova) and transgenic lines (M9/T386 and M9/T389) were not as different as when grown on their own roots. M9/T386 and M9/T389 were only temporarily less infected by scab than M9/Pinova. M9/T386 and M9/T389 did not differ significantly from M9/Pinova in their root chitinase activities, AMF root colonization and biomass.

Metais pesados como Mn e Cu, apesar de essenciais para o crescimento e desenvolvimento normal das plantas, podem ser tóxicos quando em excesso no ambiente. Para a manutenção do crescimento normal das plantas, a homeostase de metais é importante. Absorção excessiva de elementos redutores ativos causa destruição oxidativa. Dessa forma, absorção, transporte e distribuição pela planta devem ser controlados. O controle inclui o transporte precisamente direcionado a partir do nível macrotecidual para o nível micro, de células e organelas. O sistema de transporte de membranas parece desempenhar um papel muito importante no trânsito de metais. Esta revisão cobre amplamente o transporte a longa distância e o celular, como também mecanismos de destoxificação e homeostase de Mn e Cu, os quais são micronutrientes essenciais, mas extremamente tóxicos em elevadas concentrações.

Heavy metals like Mn and Cu, though essential for normal plant growth and development, can be toxic when present in excess in the environment. For normal plant growth maintenance of metal homeostasis is important. Excess uptake of redox active elements causes oxidative destruction. Thus, uptake, transport and distribution within the plant must be strongly controlled. Regulation includes precisely targeted transport from the macro-level of the tissue to the micro-level of the cell and organelles. Membrane transport systems play very important roles in metal trafficking. This review provides a broad overview of the long distance and cellular transport as well as detoxification and homeostasis mechanisms of Mn and Cu, which are essential micronutrients but extremely toxic at elevated concentrations.