Photoperiod affects the phenotype of mitochondrial complex I mutants

Plant mutants for genes encoding subunits of mitochondrial Complex I (CI, NADH:ubiquinone oxidoreductase), the first enzyme of the respiratory chain, display various phenotypes depending on growth conditions. Here, we examined the impact of photoperiod, a major environmental factor controlling plant development, on two Arabidopsis thaliana CI mutants: a new insertion mutant interrupted in both ndufs8.1 and ndufs8.2 genes encoding the NDUFS8 subunit, and the previously characterized ndufs4 CI mutant. In long day (LD) condition, both ndufs8.1 and ndufs8.2 single mutants were indistinguishable from Col-0 at phenotypic and biochemical levels, whereas the ndufs8.1 ndufs8.2 double mutant was devoid of detectable holo-CI assembly/activity, showed higher AOX content/activity and displayed a growth-retardation phenotype similar to that of the ndufs4 mutant. Although growth was more affected in ndufs4 than ndufs8.1 ndufs8.2 under short day (SD) condition, both mutants displayed a similar impairment of growth acceleration after transfer to LD as compared to the WT. Untargeted and targeted metabolomics showed that overall metabolism was less responsive to the SD-to-LD transition in mutants than in the WT. The typical LD acclimation of carbon, nitrogen-assimilation and redox-related parameters was not observed in ndufs8.1 ndufs8. Similarly, NAD(H) content, that was higher in SD condition in both mutants than in Col-0, did not adjust under LD. We propose that altered redox homeostasis and NAD(H) content/redox state control the phenotype of Complex I mutants and photoperiod acclimation in Arabidopsis

A Genotyping-by-Sequencing approach brings new insights into the population structure and local adaptation of Western Mediterranean Oaks

XIX ENBE Annual Meeting of the Portuguese Association for Evolutionary Biology, 18-19 December 2023, Lisboninfo:eu-repo/semantics/publishedVersio

Adjustment of photosynthetic carbon assimilation to higher growth irradiance in three-year-old seedlings of two Tunisian provenances of Cork Oak (Quercus suber L.)

Three-year-old seedlings of two Tunisian provenances of cork oak (Quercus suber L.) differing in climatic conditions at their geographical origin were subjected to increasing light intensities. Ga’four was the provenance from the driest site and Feija from the wettest site. Low-light adapted seedlings from both provenances were exposed to two light treatments: full sunlight (HL) and low light (LL, 15% sunlight) for 40 days. The CO2-response curve of leaf net photosynthesis (An-Ci curve) established under saturated photon flux density was used to compare photosynthetic parameters between leaves subjected to continuous low light (LL leaves) and leaves transferred from low to high light (HL leaves). Transfer from low to high light significantly increased net photosynthesis (An) and dark respiration (Rd) in Ga’four provenance but not in Feija. After transfer to high irradiance, specific leaf area (SLA) did not change in either provenance. This suggested that the increase in photosynthetic capacity on a leaf area basis in HL leaves of Ga’four provenance was not due to increased leaf thickness. Only the seedlings from the Ga’four provenance were able to acclimate to high light by increasing Vcmax and Jmax

Light acclimation of leaf gas exchange in two Tunisian cork oak populations from contrasting environmental conditions

Due to diverse environmental conditions, Mediterranean plant populations are exposed to a range of selective pressures that may lead to phenotypic plasticity and local adaptation. We examined the effect of light acclimation on photosynthetic capacity in two Quercus suber (L.) populations that are native to different ecological conditions. Low-light adapted seedlings from both populations were exposed to three light treatments: full sunlight (HL), medium light (ML, 43% sunlight) and low light (LL, 15% sunlight) for one month. Photosynthetic performance was monitored by measuring leaf gas exchange and chlorophyll fluorescence parameters. The light environment influences light-saturated carbon assimilation (Amax) in the leaves of the population inhabiting the hot and dry region (from Gaafour). In contrast, there was no significant difference in Amax between leaves grown in high light and low light from Feija (the population native to a cold and humid climate), which suggests an inability of the Feija population to adjust its photosynthesis to respond to higher irradiance. The inability of the Feija population to adjust its photosynthesis did not result from a light acclimation failure in terms of chlorophyll content and ratio compared with the Gaafour population. Instead, it seems to be the consequence of lower stomatal conductance in the Feija population at HL compared to Gaafour

A Genotyping-by-Sequencing Approach Brings New Insights into the Population Structure and Local Adaptation of Western Mediterranean Oaks.

The Mediterranean region has been described as a ‘climate change hotspot’, with increased temperatures and decreased precipitation expected to affect the region in the coming decades. Given the pace and intensity at which these changes are expected to happen, it becomes important to understand species capacity to respond to climate change. Species response to environmental change can happen through phenotypic plasticity, range shift, or genetic adaptation to their new conditions. In order to understand a species adaptive capacity to respond to climate change, it is important to disentangle how much of its genetic diversity is the result of population structure, and how much results from the action of natural selection. This work involved samples of Cork Oak (Quercus suber) and Holm Oak (Quercus ilex and Quercus rotundifolia), collected throughout the species range, with special attention given to the Western Mediterranean basin. Genotyping by Sequencing was employed to generate several genome wide Single Nucleotide Polymorphism datasets, which were used (i) to investigate population structure using several complementary approaches, and (ii) to detect evidence of local adaptation through a Landscape Genomics approach involving the detection of genetic-environmental associations with several bioclimatic variables. This work builds on previous analyses of Cork Oak SNP data, and is, to our knowledge, the first attempt to use genome-wide nuclear genetic markers to uncover the existence of population structure and signatures of local adaptation in Holm oak. Our results reveal contrasting patterns of population structure and differentiation. Holm Oak shows a marked pattern of population structure and considerable differentiation, especially between Q. rotundifolia and Q. ilex samples, which brings support to the status of Q. ilex and Q. rotundifolia as two genetically distinct species. Cork Oak, on the other hand, shows much less pronounced population structuring, as reported in previous works based on nuclear genetic markers. Furthermore, a considerable degree of differentiation is observed between Iberian and Moroccan populations of Q. rotundifolia, which is not observed for Q. suber. Additionally, we uncover the relatively unstructured nature of the Iberian Q. rotundifolia and Q. suber populations. We also identified a considerable number of putative SNPs under selection in both species, showing association with multiple bioclimatic variables related to temperature and precipitation. Annotation of the genomic regions harboring these putative SNPs revealed several genes potentially associated with heat and water stress. In general, these results build on previous knowledge regarding the population structure of Cork Oak and bring new insights into the population structure of Holm Oak, contributing towards the clarification of its taxonomy, which up until this point has suffered from a lack of consistency. Regarding the detection of local adaptation, our results serve as a first step in understanding the capacity of Cork Oak and Holm Oak to respond to future climate change, opening the door to more complex analyses, such as genomic prediction of maladaptation, which may help identify areas of the species’ distribution especially sensitive to climate change, and inform future management efforts towards the conservation of these species