Transgenic poplar expressing Arabidopsis NDPK2 enhances growth as well as oxidative stress tolerance

Abstract

SummaryNucleoside diphosphate kinase 2 (NDPK2) is known to regulate the expression of antioxidant genes in plants. Previously, we reported that overexpression of Arabidopsis NDPK2 (AtNDPK2) under the control of an oxidative stress-inducible SWPA2 promoter in transgenic potato and sweetpotato plants enhanced tolerance to various abiotic stresses. In this study, transgenic poplar (Populus alba · Poplus glandulosa) expressing the AtNDPK2 gene under the control of a SWPA2 promoter (referred to as SN) was generated to develop plants with enhanced tolerance to oxidative stress.The level of AtNDPK2 expression and NDPK activity in SN plants following methyl viologen (MV) treatment was positively correlated with the plant's tolerance to MV-mediated oxidative stress. We also observed that antioxidant enzyme activities such as ascorbate peroxidase, catalase and peroxidase were increased in MV-treated leaf discs of SN plants. The growth of SN plants was substantially increased under field conditions including increased branch number and stem diameter. SN plants exhibited higher transcript levels of the auxin-response genes IAA2 and IAA5. These results suggest that enhanced AtNDPK2 expression affects oxidative stress tolerance leading to improved plant growth in transgenic poplar.

Transgenic poplar expressing AtNDPK2 exhibits enhanced biomass in the LMO field

“…glandulosa, clone Hyun3) plant lines (SN3 and SN4) with high levels of AtNDPK2 expression, enhanced plant growth and tolerance to oxidative stress were selected for study (Kim et al 2011). An AtNDPK2 gene overexpression vector was constructed using an oxidative-inducible SWPA2 promoter of sweetpotato and a CaMV 35S terminator sequence in the pCAMBIA2300 plant expression vector, as described previously (Kim et al 2009).…”

“…In a previous study, SN transgenic poplar plants were transplanted to field conditions and grown for a season to produce enough cuttings for growth performance tests (Kim et al 2011). The following spring, cuttings were prepared from the stems of transgenic plants.…”

“…Linear data were normalized to the mean CT of β-actin as reference gene. Primer sets of the AtNDPK2, actin and IAA genes were described previously (Kim et al 2011). …”

“…It has been determined previously that SN poplar plants show increased transcript levels of auxin-responsive genes under field conditions (Kim et al 2011). As altered plant growth and biomass were found in the transgenic lines under field conditions of the second growing season, quantitative RT-PCR analyses were conducted to characterize the expression patterns of a variety of Aux/IAA genes in these transgenic lines (Fig.…”

“…Transgenic potato and sweetpotato plants expressing AtNDPK2 under the control of the oxidative stress-inducible SWPA2 promoter were generated and shown to possess enhanced tolerance to multiple environmental stresses such as salt, drought and extreme temperatures (Tang et al 2008;Kim et al 2009). Recently, it was also noted that the AtNDPK2 expressed in transgenic poplar plants (referred to as SN poplar plants) resulted in higher antioxidant enzyme levels and enhanced auxin-responsive gene expression; accordingly, growth rates and tolerance to oxidative stress of transgenic poplar plants increased under greenhouse and field conditions in 2009 (Kim et al 2011). …”