The aquaporin PIP2;5 contributes to maize root growth and development

Plants being sessile organisms, they have evolved various mechanisms to adapt to water scarcity. Roots exhibit plasticity in their branching patterns to forage efficiently resources in heterogeneous soils. The right positioning of lateral roots in prevailing areas is crucial for plant survival. Aquaporins, which facilitate the membrane diffusion of water and small solutes, contribute to the development and maintenance of primary and lateral roots. In this thesis, we hypothesize that aquaporins are involved in root formation and growth in response to local water deprivation. To test this hypothesis, a sandwich system was developed in which roots were placed between two agar layers with different osmolarities to induce a hydropatterning stimulus, and the effects of PIP2;5 overexpressing or knockout on lateral root formation were observed. PIP2;5 overexpression resulted in the formation of a higher number of lateral roots in response to water stress compared with the wild type plants, while the pip2;5 knock-out line produced less lateral roots. Next, we induced a xerobranching stimulus of different duration in different culture systems. During a short water stress (10h), no difference in the number of lateral roots was observed in the different lines. However, when roots were exposed to longer, permanent water stress, PIP2;5 overexpressing or knockout lines led to the formation of more and less lateral roots in the repression zone, respectively, compared to the wild type plants. Lastly, the use of confocal imaging to study the expression pattern of YFP-PIP2;5 in lateral roots suggested that PIP2;5 controls lateral root emergence by ensuring the passage of the lateral root primordium through the outer cell layers. Altogether, these results provide new insights into processes underlying lateral root development in response to water availability and suggest potential strategies for enhancing plant resilience to drought. These findings may have practical applications in plant breeding and crop management, as well as in plant biology research.