T-DNA insertion in aquaporin gene AtPIP1;2 generates transcription profiles reminiscent of a low CO2 response

Results from CO2 diffusion studies and characterization of Arabidopsis thaliana aquaporin AtPIP1;2T-DNA insertion lines support the idea that specific aquaporins facilitate the diffusion of CO2 through biological membranes. However, their function as CO2 diffusion facilitators in plant physiology is still a matter of debate. Assuming that a lack of AtPIP1;2 causes a characteristic transcriptional response, we compared data from a AtPIP1;2T-DNA insertion line obtained by Illumina sequencing, Affymetrix chip analysis and quantitative RT-PCR to the transcriptome of plants grown under drought stress or under low CO2 conditions. The plant reaction to the deficit of AtPIP1;2 was unlike drought stress responses but comparable with that of low CO2 conditions. In addition, we observed a phenotype characteristic to plants grown under low CO2. The findings support the hypothesis that the AtPIP1;2 function in plant physiology is not to facilitate water but CO2 diffusion. The results from a transcriptome analysis of an Arabidopsis thaliana T-DNA insertion mutant line provide evidence that the product of the respective gene AtPIP1;2 caused an answer related to a limitation of CO2 diffusion. To our opinion, it provides an important argument to the ongoing debate about the significance of these kinds of aquaporins: whether the protein is a component of drought stress management or facilitates CO2 diffusion.