LIVESEED (https://www.liveseed.eu/) is a European Research project that integrates seed production companies and research/breeding Institutes focused on the development of more resilient varieties to more efficiently cope with environmental constraints. Organic agriculture, recognized as a more sustainable agricultural system, strongly depends on the use of highly resilient genotypes. In this context, it is extremely important to develop new phenotyping techniques for selecting useful genotypes, in particular at the seed level. Current research at UEvora in the LIVESEED project uses calorespirometry as a phenotyping tool to investigate the link between seed germination and the alternative oxidase (AOX) respiratory pathway. Seed germination involves the activation of several metabolic pathways, including cellular respiration. AOX plays a crucial role in regulating cell reprogramming by controlling metabolic transitions related to the cellular redox state and the variable carbon balance. To assess the involvement of AOX in P. sativum L. (PsAOX) germination, seeds of four cultivars (‘Respect-1’, ‘S134’, ‘G78’ and ‘S91’) were imbibed in sterile tap water for 16h and calorespirometric parameters (heat and CO₂ emission rates) measured at 25°C using a Multi-Cell Differential Scanning Calorimeter in isothermal mode. Additionally, the involvement of PsAOX was evaluated by transcript quantification (PsAOX1, PsAOX2a, and PsAOX2b) through RT-qPCR, and by analysis of AOX expression through Western blot.

The results demonstrate that the cv. ‘S91’, characterized by a low germination rate, also exhibited the lowest metabolic heat and respiration rate. However, contrary to expectations, PsAOX transcript accumulation and PsAOX protein expression were significantly higher for ‘S91’ than for the other cultivars. These results demonstrate the applicability of calorespirometry to seed phenotyping and the involvement of AOX in seed germination.

Acknowledgments: This work was supported by the EU project LIVESEED - Improve performance of organic agriculture by boosting organic seed and plant breeding efforts across Europe funded by the European Union's HORIZON 2020 research and innovation programme under the Grant Agreement no 727230, and by the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number 17.00090; and by National Funds through FCT under the Project UIDB/05183/2020. Authors are very thankful to IIFA for the fellowship given to Lénia Rodrigues. The opinions expressed and arguments employed herein do not necessarily reflect the official views of the EC and the Swiss government. Neither the European Commission/SERI nor any person acting behalf of the Commission/SERI is responsible for the use which might be made of the information provided on this document.