Abstract

In several plant species, transcriptional studies have detected genes repressed in hypoxia, such as those related to the TCA cycle and amino acid synthesis. However, Ala and GABA accumulate during hypoxic stimulation, being considered a hypoxia adaptive plant response as important as the fermentative pathways. Normally, GABA levels are low, but increase rapidly and extensively in response to stress (e.g. hypoxia), so the GABA shunt pathway has become a focus of interest in the study of plant adaptations to stress. Studies with Arabidopsis mutants for GABA synthesis pathway genes have demonstrated both transcriptional and enzymatic modulation of GABA shunt as consequence of Ca++ cellular signaling and cytosolic acidosis, both conditions typically triggered by hypoxia. A recent RNA-Seq study revealed a differential transcriptional response of some of the genes of the GABA shunt pathway between genotypes of Prunus rootstocks subjected to hypoxia, with higher levels of their transcripts being detected in the tolerant genotype (Mariana 2624) compared to the sensitive (Mazzard F12/1). Thus, it is hypothesized that "high levels of GABA determine greater tolerance to hypoxia stress in Prunus rootstocks". To test this hypothesis, genotypes with contrasting tolerance will be subjected to hypoxia and their physiological response and GABA metabolism (transcriptional and biochemical) will be characterized. In addition, the analysis will be extended to the evaluation of the effect of exogenous application of GABA and calcium on the metabolism of endogenous GABA in the response of plants to hypoxia. In this way, the present project is coherently framed within the CEAF guidelines aimed at gaining a better understanding of the mechanisms involved in the determination of hypoxia stress tolerance in rootstocks of the Prunus genus, relevant information for the development of the breeding program of Prunus rootstocks that takes place in this Regional Center.