Overexpression of a pine Dof transcription factor in hybrid poplars: A comparative study in trees growing under controlled and natural conditions

Abstract

In this work, the role of the pine transcriptional regulator Dof 5 in carbon and nitrogen metabolism has been examined in poplar trees. The overexpression of the gene and potential effects on growth and biomass production were compared between trees growing in a growth chamber under controlled conditions and trees growing in a field trial during two growth seasons. Ten-week-old transgenic poplars exhibited higher growth than untransformed controls and exhibited enhanced capacity for inorganic nitrogen uptake in the form of nitrate. Furthermore, the transgenic trees accumulated significantly more carbohydrates such as glucose, fructose, sucrose and starch. Lignin content increased in the basal part of the stem likely due to the thicker stem of the transformed plants. The enhanced levels of lignin were correlated with higher expression of the PAL1 and GS1.3 genes, which encode key enzymes involved in the phenylalanine deamination required for lignin biosynthesis. However, the results in the field trial experiment diverged from those observed in the chamber system. The lines overexpressing PpDof5 showed attenuated growth during the two growing seasons and no modification of carbon or nitrogen metabolism. These results were not associated with a decrease in the expression of the transgene, but they can be ascribed to the nitrogen available in the field soil compared to that available for growth under controlled conditions. This work highlights the paramount importance of testing transgenic lines in field trials.

Nitrogen Metabolism and Biomass Production in Forest Trees

“…The transcription factor Dof5 that regulates GS1 isoforms in maritime pine ( Rueda-López et al, 2008 ) was overexpressed in hybrid poplars ( Figure 2B ). In comparison to untransformed controls, young transgenic plants exhibited enhanced growth, an increased capacity for inorganic N uptake, and accumulated significantly more carbohydrates and lignin ( Rueda-López et al, 2017 ).…”

“…Interestingly, these transgenic lines showed attenuated growth and no modification of carbon or N metabolism when growing under natural conditions. As the expression of the transgene was stable during the period of study the observed differences in the performance of transgenic trees were attributed to the low levels of N nutrients available in the soil ( Rueda-López et al, 2017 ). These findings reinforce the importance of field studies and indicate that the manipulation of structural rather than regulatory genes has been more effective for increasing biomass production and forest productivity.…”

The Arabidopsis Transcription Factor CDF3 Is Involved in Nitrogen Responses and Improves Nitrogen Use Efficiency in Tomato

“…DNA binding with one finger (DOF) TFs are a group of plant specific proteins that contain a highly conserved DNA binding domain of 52 amino acids, with a C2-C2 structure that binds to a 5-T/AAAAG-3 DNA sequence motif (Yanagisawa and Schmidt, 1999). Different reports showed that DOF proteins are involved in a wide range of developmental processes such as root growth, seed development, and flowering time (Yanagisawa, 2002;Noguero et al, 2013;Rueda-Lopez et al, 2017). In addition, maize ZmDOF1 and ZmDOF2 have been also implicated in nitrogen assimilation and C/N balance (Yanagisawa and Sheen, 1998;Yanagisawa, 2004;Peña et al, 2017).…”

SNPeffect: identifying functional roles of SNPs using metabolic networks

“…PAL is responsible for converting phenylalanine to cinnamic acid, which constitutes the first dedicated step of lignin biosynthesis in poplar. PAL overexpression has been observed to negatively impact plant growth in transgenic poplar (Rueda‐López et al , 2017). HCT catalyzes the transfer of the caffeoyl moiety of 5‐ O ‐caffeoylquinate onto CoA (producing caffeoyl‐CoA and quinate) and transgenic poplar with downregulated HCT genes exhibit slower growth and thinner stems than wild‐type (Peng et al , 2014; Zhou et al , 2018).…”