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- Gene transcripts responsive to drought stress identified in Citrus macrophylla bark tissue transcriptome have a modified response in plants infected by Citrus tristeza virusPublication . da Silva, Melina; Pinto, Patricia IS; Guerra, Rui Manuel Farinha das Neves; Duarte, Amilcar; Power, Deborah; Marques, N T.Citrus macrophylla Wester (CM) has valuable agronomic characteristics such as the ability to grow in saline soils, although with low tolerance to prolonged drought stress (DS). To understand the mechanisms that characterize CM response to water scarcity, this study compared transcriptome profile changes in CM stem tissue when exposed to DS and identified a total of 2745 differentially expressed transcripts (DETs, fold change > 2), of which 631 were up-regulated and 2114 were down-regulated. DETs up-regulated by DS were enriched in pathways such as the redox and osmotic system or soluble carbohydrates and in transcripts for low molecular weight proteins such as late embryogenesis abundant protein (LEA). Down-regulated transcripts were mainly assigned to photosynthesis, transport, phenylpropanoids, calcium dependent kinases, brassinosteroids and other hormones including salicylic acid and abscisic acid. To assess the interplay between DS and Citrus tristeza virus (CTV) infection, twelve genes were profiled by quantitative Real-Time PCR (qPCR) analysis in control and CTV-infected CM plants, with or without DS. The twelve analyzed transcripts were significantly correlated (r = 0.82, p < 0.001) with the RNA-Seq results and gave insight into the responses of CM to drought and/or to infection with CTV. Transcriptome results unveiled highly responsive genes to DS in stem tissue, which may be candidates for genetic selection of high drought tolerant plants of CM.
- Physiology, endocrinology and chemical communication in aggressive behaviour of fishesPublication . Silva, Melina da; Canario, Adelino; Hubbard, Peter; Goncalves, David Manuel FloresFishes show remarkably diverse aggressive behaviour. Aggression is expressed to secure resources; adjusting aggression levels according to context is key to avoid negative consequences for fitness and survival. Nonetheless, despite its importance, the physiological basis of aggression in fishes is still poorly understood. Several reports suggest hormonal modulation of aggression, particularly by androgens, but contradictory studies have been published. Studies exploring the role of chemical communication in aggressive behaviour are also scant, and the pheromones involved remain to be unequivocally characterized. This is surprising as chemical communication is the most ancient form of information exchange and plays a variety of other roles in fishes. Furthermore, the study of chemical communication and aggression is relevant at the evolutionary, ecological and economic levels. A few pioneering studies support the hypothesis that aggressive behaviour, at least in some teleosts, is modulated by "dominance pheromones" that reflect the social status of the sender, but there is little information on the identity of the compounds involved. This review aims to provide a global view of aggressive behaviour in fishes and its underlying physiological mechanisms including the involvement of chemical communication, and discusses the potential use of dominance pheromones to improve fish welfare. Methodological considerations and future research directions are also outlined.
- Callose synthase and xyloglucan endotransglucosylase gene expression over time in Citrus × clementina and Citrus × sinensis infected with citrus tristeza virusPublication . da Silva, Melina; Germano, Sandra; Duarte, Amilcar; Pinto, Patrícia; Marques, NatáliaCitrus tristeza virus (CTV) is a virus that already caused great losses in citrus producing regions. The cell wall of plant cells plays an important role in the defence response to viruses. Following several studies indicating that cell wall enzyme transcripts of callose synthase 7 (calS7) and xyloglucan endotransglucosylase 9 (xth9) are modified during a viral infection, transcript expression of calS7 isoform x5 (calS7x5) and xth9 was evaluated over time in Citrus x sinensis 'Valencia Late' (VL) and Citrus x clementina 'Fina' (CL), infected with the severe CTV isolate T318A, by quantitative (q) PCR. qPCR analysis of healthy and CTV infected citrus was performed at 15 days, 10 months and at 31 months post-inoculation (dpi/mpi), respectively. The CTV titer, evaluated at the three time-points by qPCR, increased over time in bark tissues, with VL plants exhibiting a titer about 5 times higher than CL 31 mpi. CTV infection did not cause significant changes in calS7x5 gene expression over time in both citrus cultivars. However, CTV infection was associated with significant up-regulation of xth9 in VL compared to controls 31 mpi. This study highlights that CTV infection can affect the expression of specific cell wall-associated genes over time and that this influence was distinct for VL and CL. This study provides further insight into the CTV-citrus host interaction, with the long-term response of VL to a severe CTV isolate involving a high expression of the xth9 gene.
- High variability in aggression and habituation to the mirror assay in ornamental Siamese fighting fish Betta splendensPublication . Coelho da Silva, Melina; Canario, Adelino; Hubbard, Peter; Cardoso, Sara D.; Gonçalves, DavidUnderstanding consistent inter-individual variability in animal behaviour, known as personality traits, is essential for exploring the mechanisms and evolutionary consequences of behavioural diversity. Aggressive behaviour influences survival, resource acquisition, and reproduction, so clarifying individual differences can enhance our understanding of ecological dynamics and improve experimental design accuracy in behavioural studies. In this study, ornamental male Betta splendens, a model organism for aggression research, were analysed for intra- and inter-individual variability in aggressive responses to their mirror image—a standard method for assessing aggression in fish—once per week, and their consistency was evaluated over three consecutive weeks There were significant differences in aggressive behaviour across individuals, with coefficients of variation ranging from 29 to 60%. While most fish exhibited the full suite of aggressive displays, some showed no aggressive behaviour, while others only displayed threat behaviours but did not advance to the attacks. The consistency of individual threat and attack behaviours varied, but repeatability was high overall (intra-class correlation coefficients≥0.5), indicating that individual fish have different levels of aggression. There was habituation to the mirror assay, with aggression decreasing significantly by the second week, though the degree of habituation, a form of learning, varied among individuals in some behaviours. Air-breathing frequency correlated positively with aggression behaviours and can be considered an indicator to infer aggression level in this species. These results indicate that inter-individual variation in aggressive behaviour and habituation to repeated testing using the mirror assay should be considered in aggression studies using B. splendens and potentially in other species.