A putative poplar PP2C-encoding gene negatively regulates drought and abscisic acid responses in transgenic Arabidopsis thaliana

Key message: Here we link for the first time a poplar gene with putative function in ABA signaling to the regulation of drought responses, providing a target for drought tolerance improvement in poplars. Populus species are valued for their fast growth and are cultivated widely. Many of the commonly used species and hybrids are, however, regarded as drought sensitive, which poses a problem for large-scale cultivation particularly in light of climate change-induced drought spells in areas of poplar growth. While many hundreds of drought-induced genes have been identified in Populus species, very little is known about the genes and the signaling process that leads to a drought response in these species. Based on sequence similarity, the poplar G059200 gene is a potential ortholog of AtPP2CA, an inhibitor of drought and abscisic acid (ABA) responses in Arabidopsis thaliana. To test if G059200 has a similar function, we generated transgenic A. thaliana plants overexpressing this gene. These transgenic lines exhibited reduced responses to exogenous ABA and reduced tolerance to osmotic stress. Finally, drought tolerance of plants was also significantly reduced. Taken together, these data provide evidences that G059200 acts as a negative regulator of ABA responses. The ability to negatively regulate drought stress responses suggests that G059200 may be targeted for drought tolerance breeding, for example, by identification of individuals harboring natural or induced loss-of-function alleles, or by RNA interference technology, to generate poplar plants with reduced activity of G059200.