Role of aquaporins in maize root hydropatterning

During growth, plant roots are exposed to heterogeneous soil water availability. This heterogeneity would change the root developmental processes and its anatomy. The phenomenon is called hydropatterning. In root side facing dry soil or air, an absence or delay in lateral root development and a formation of root cortical aerenchyma are observed. These modifications are dependent on auxin variation and gene expression changes. As aquaporins are essential players in water distribution, cell turgor maintenance and primary and lateral root development, we hypothesize that aquaporins are also involved in the hydropatterning process. The aim of this work was therefore to determine whether plasma membrane aquaporins (PIPs, plasma membrane intrinsic proteins) play a role in maize root hydropatterning. To this aim, we set-up the system to study hydropatterning. It consists of a sandwich with one side being an agar slab and the other a plastic. We analyzed hydropatterning in different maize lines: two lines deregulated in PIP2;5 expression and their respective wild-type (WT) lines. PIP2;5 is one of the most expressed aquaporin in maize roots and lines overexpressing it or knock out for this gene are available in the laboratory (Hachez et al., 2006 and 2012). We found that less lateral root and more aerenchyma were formed in the side facing the air or plastic side, but no differences were observed in the deregulated PIP2;5 lines compared to the WT lines. Some differences in aquaporin expression were detected (real time quantitative PCR (RT-qPCR), western blot and immunocytochemistry) during hydropatterning, but new experiments will be required to demonstrate the importance of aquaporins in hydropatterning.