Mitochondrial uncoupling proteins (UCPs) are mitochondrial inner membrane proteins that dissipate the proton electrochemical gradient generated by the respiratory chain complexes. In plants, these proteins are crucial for maintaining mitochondrial reactive oxygen species (ROS) homeostasis. In this study, single T-DNA insertion mutants for two (AtUCP1 and AtUCP2) out of the three UCP genes present in Arabidopsis thaliana were employed to elucidate their potential roles in planta. Our data revealed a significant increase in the Adenosine triphosphate (ATP)/Adenosine diphosphate (ADP) ratios of both mutants, indicating clear alterations in energy metabolism, and a reduced respiratory rate in atucp2. Phenotypic characterization revealed that atucp1 and atucp2 plants displayed reduced primary root growth under normal and stressed conditions. Moreover, a reduced fertility phenotype was observed in both mutants, which exhibited an increased number of sterile siliques and a lower seed yield compared with wild-type plants. Reciprocal crosses demonstrated that both male fertility and female fertility were compromised in atucp1, while such effect was exclusively observed in the male counterpart in atucp2. Most strikingly, a pronounced accumulation of hydrogen peroxide in the reproductive organs was observed in all mutant lines, indicating a disturbance in ROS homeostasis of mutant flowers. Accordingly, the atucp1 and atucp2 mutants exhibited higher levels of ROS in pollen grains. Further, alternative oxidase 1a was highly induced in mutant flowers, while the expression profiles of transcription factors implicated in gene regulation during female and male reproductive organ/tissue development were perturbed. Overall, these data support the important role for AtUCP1 and AtUCP2 in flower oxidative homeostasis and overall plant fertility.

Phytophthora nicotianae Breda de Haan (Phytophthora parasitica Dastur) causes severe damage to citrus crops worldwide. A population of citrandarins was created from the cross between the susceptible parent Citrus sunki Hort. Ex Tan. and the resistant parent Poncirus trifoliata (L.) Raf. cv. Rubidoux, both parents and two reference rootstocks (Rangpur lime and Swingle citrumelo) were grafted in a greenhouse on Rangpur lime. Inoculations were performed at 10 cm and 15 cm above the grafting region and the resulting lesions were evaluated by measuring the lesion length 60 days after inoculation. As control, non-inoculated plants of each genotype were used. In addition, we evaluated the expression of 19 candidate genes involved in citrus defense response 48 h after pathogen infection by quantitative Real-Time PCR (qPCR). We mapped genomic regions of Quantitative Trait Loci (QTLs) and Expression Quantitative Trait Loci (eQTLs) associated with resistance to P. parasitica in the linkage groups (LGs) of the previously constructed maps of C. sunki and P. trifoliata. We found disease severity differences among the generated hybrids, with lesion lengths varying from 1.15 to 11.13 mm. The heritability of the character was 65%. These results indicate that there is a great possibility of success in the selection of resistant hybrids within this experiment. The analysis of gene expression profile demonstrated a great variation of responses regarding the activation of plant defense pathways, indicating that citrandarins have several defense strategies to control oomycete infection. The information of the phenotypic and gene expression data made possible to detect genomic regions associated with resistance. Three QTLs and 84 eQTLs were detected in the linkage map of P. trifoliata, while one QTL and 110 eQTLs were detected in C. sunki. This is the first study to use eQTLs mapping in the Phytophthora-citrus interaction. Our results from the QTLs and eQTLs mapping allow us to conclude that the resistance of some citrandarins to the infection by P. parasitica is due to a favorable combination of QTLs and eQTLs transmitted by both parents.

Plant dicarboxylate carriers (DICs) transport a wide range of dicarboxylates across the mitochondrial inner membrane. The Arabidopsis thalianaDIC family is composed of three genes (AtDIC1, 2 and 3), whereas two genes (EgDIC1 and EgDIC2) have been retrieved in Eucalyptus grandis. Here, by combining in silico and in planta analyses, we provide evidence that DICs are partially redundant, important in plant adaptation to environmental stresses and part of a low-oxygen response in both species. AtDIC1 and AtDIC2 are present in most plant species and have very similar gene structure, developmental expression patterns and absolute expression across natural Arabidopsis accessions. In contrast, AtDIC3 seems to be an early genome acquisition found in Brassicaceae and shows relatively low (or no) expression across these accessions. In silico analysis revealed that both AtDICs and EgDICs are highly responsive to stresses, especially to cold and submergence, while their promoters are enriched for stress-responsive transcription factors binding sites. The expression of AtDIC1 and AtDIC2 is highly correlated across natural accessions and in response to stresses, while no correlation was found for AtDIC3. Gene ontology enrichment analysis suggests a role for AtDIC1 and AtDIC2 in response to hypoxia, and for AtDIC3 in phosphate starvation. Accordingly, the investigated genes are induced by submergence stress in A. thaliana and E. grandis while AtDIC2 overexpression improved seedling survival to submergence. Interestingly, the induction of AtDIC1 and AtDIC2 is abrogated in the erfVII mutant that is devoid of plant oxygen sensing, suggesting that these genes are part of a conserved hypoxia response in Arabidopsis.

A positive influence of temperature and precipitation was observed on floral and fruit development of Passiflora trintae Sacco. This study described the floral biometrics and characterized the reproductive phenology based on local climatic factors (temperature and precipitation) of a natural population of P. trintae in southwestern Bahia State, Brazil. According to the floral morphometry results, data were obtained that can be used in future taxonomic studies and for exploring diversity by making interspecific crosses with other species of the same genus. Under the study conditions, a higher production of flower buds and flowers at anthesis, as well as flowering peak, occurred during the summer months, while a higher production of ripe and immature fruits, as well as fruiting peak, coincided and occurred during the spring. The period of floral anthesis begins at around 04:30 a.m. and ends at around 04:00 p.m. Temperature can predict the phenological variables of flowering peak and flower bud rate, while precipitation can predict all phenological variables related to flower bud rate, flowering rate, flowering peak, fruiting rate, and fruiting peak. Biometria floral e caracterização fenológica da floração e frutificação para o maracujá Passiflora trintae no Sudoeste da Bahia, Brasil. Foi observada uma influência positiva da temperatura e precipitação no desenvolvimento floral e de frutos em Passiflora trintae Sacco. Este estudo descreveu a biometria floral e caracterizou a fenologia reprodutiva a partir de fatores climáticos locais da temperatura e precipitação em uma população natural de P. trintae localizada no sudoeste do estado Bahia, Brasil. De acordo com os resultados da morfometria floral, foram obtidos potenciais dados para futuros estudos taxonômicos, além de permitir explorar a diversidade por cruzamentos interespecíficos com outras espécies do mesmo gênero. Nas condições deste estudo, foi registrado que a maior produção de botões florais, incidência de flores em antese e o pico de floração ocorreram durante os meses de verão, enquanto que a maior produção de frutos maduros e imaturos, bem como o pico de frutificação, coincidiram e ocorreram durante a primavera. Foi possível estabelecer o período de antese floral que se inicia em torno de 04h30min e termina em torno de 16h00min. A temperatura pode predizer as variáveis fenológicas do pico de florescimento e taxa de botões florais, enquanto que a precipitação pode predizer todas as variáveis fenológicas relacionadas à taxa de botões florais, taxa de florescimento, pico de florescimento, taxa de frutificação e pico de frutificação.