The ‘MitoNuEco’ project examined phenotypes in a total of 48 experimental groups, comprising four fly lines (coadapted and cybrid lines), two sexes, two temperatures (25°C and 29°C) and three diets (standard, high-carbohydrate and high-protein diets). Work was performed via 9 work packages (WPs). WPs 1-2 covered life-history traits characterization, including female and male fitness, development, survival, thermal tolerance, longevity and locomotor activity. Gene expression analysis was managed under WPs 3-5. WPs 6-7 focused on both mitochondrial and organismal respirometry (mitochondrial O2 and reactive oxygen species fluxes, plus CO2 efflux), and estimation of mitochondria content.
Results of the ‘MitoNuEco’ project revealed a robust phenotypic effect resulting from mitonuclear interactions. Even in absence of external stressors, cybrid lines display overall increased rates of mitochondrial respiration together with low ROS efflux compared to parental populations. This metabolic remodelling likely indicates impairment of mitochondrial function, as cybrids suffered from slower development, low fertility and reduced lifespan compared to coevolved populations. Ecological stressors also had a pervasive impact on fly performance, exacerbating mitonuclear breakdown and favouring coadapted populations. Exposure to high temperatures (29°C) negatively impacted aerobic capacity, especially in cybrids, which also experienced reduced lifespan and accelerated reproductive senescence. As for thermal stress, exposure to a carbohydrate-rich diet reduced cybrids aerobic performance, and this was accompanied by reduced larval growth but increased fecundity at young age. In a nutshell, the findings of the ‘MitoNuEco’ project indicate that intergenomic interactions play a crucial role in shaping individual phenotypes. Even subtle genetic variation can give rise to mitonuclear incompatibilities, affecting aerobic metabolism and overall fitness. Additionally, results indicate that ecological stressors have the potential to aggravate the situation, potentially influencing the ability of population to persist in a scenario of increased environmental instability.
The project has delivered two main papers, one under review for Evolution Letters (preprint doi: 10.1101/2023.09.25.559268) and another published in Bioenergetic Communications (doi: 10.26124/bec:20 23-0003). Four additional manuscripts, including a conference proceeding, are currently underway. Findings were presented at departmental meetings and international conferences, including ‘CLOE JGM’ (UCL, 06/2022), ‘CBER-CLOE’ (UCL, 12/2022), ‘Bioblast 2022’ (Innsbruck, 06/2022), ‘SEB22’ (Montpellier, 07/2022) and ‘SEB23’ (Edinburg, 07/2023). The project and its main findings have also been divulged to the general public during the ‘Pint of Science 2023’ festival (London, 05/2023) (WP 8).
Transfer of knowledge included training in life-history phenotyping, RNASeq, qPCR and respirometry approaches. Mentoring was implemented by supervising six students and serving as guest lecturer for BIOL0011 and BIOL0058 UCL courses. Communication involved promoting the project’s focal theme through social media and targeted sessions for both scientific and general audiences. This included organizing sessions at "Pint of Science” Festival and ‘SEB23’ Centenary Conference, as well as participating in the 'In2ScienceUK' 2023 program, where I exposed my research to students (WP 8). Lastly, I perfected my proposal writing skills, securing fundings from the Leverhulme Trust (R-CoI) to implement future research (WP 9).
