Valutazione dei tipi cellulari coinvolti nella sopravvivenza di apici radicali mediata da etilene durante ipossia

Flooding events are becoming increasingly frequent and intense due to climate change, impacting the agricultural sector worldwide. In flooded conditions, gas exchange and, in particular, oxygen diffusion is hampered, subjecting hypogeal structures to hypoxia, and accumulating the gaseous hormone ethylene at root level due to passive physical entrapment. Previous studies demonstrated that ethylene accumulation represents an early and reliable flood signal and showed that, in Arabidopsis, an ethylene pre-treatment can prepare the root to the following hypoxic stress, enhancing its survival. While the positive effect of ethylene on the activation of adaptive responses protecting the root meristem has been confirmed, it is yet unknown how this protection is conferred, and which tissues are specifically involved. This work focused on designing and optimizing an experimental process to explore the cell type specific role of ethylene in hypoxic stress, making use of mutated Arabidopsis lines that express the ethylene-signaling disruptors EBF1 and EBF2 in a cell type specific manner. The goal was to identify which tissues could be specifically involved in the regulation of ethylene-mediated hypoxia adaptive responses. Root tip survival, intended as the capability of the root to resume growth during recovery after the hypoxic stress occurred, was measured and linked to the effectiveness of the ethylene pre-treatment on the mutated lines. The root tip survival assay identified pQ6::EBF1, pQ6::EBF2 and pQ4::EBF1, disrupting ethylene in QC and CEI, as lines insensitive to the ethylene pre-treatment, suggesting a QC and CEI potential involvement in the regulation of ethylene-mediated responses. A differential role of EBF1 and EBF2 in modulating the responses on CEI was highlighted by pQ4::EBF1 and pQ4::EBF2 results. All four pQ4 and pQ6 lines were selected to go through a second phase of analyses, aiming the evaluation of potential effects of the experimental combination of ethylene pre-treatment and hypoxic treatment on the meristem, particularly on RAM size, through confocal microscopy analyses and subsequent image processing. Such study did not reveal a clear effect of ethylene pre-treatment but suggested a possible hypoxic positive regulation on RAM size.