COI1-dependent jasmonate signalling affects growth, metabolites production and cell wall protein composition in Arabidopsis

Background and Aims: Cultured cell suspensions have been the preferred model to study the apoplast as well as to monitor metabolic and cell cycle-related changes. Previous work showed that methyl jasmonate (MeJA) inhibits leaf growth in a CORONATINE INSENSITIVE 1 (COI1)-dependent manner, with COI1 being the jasmonate (JA) receptor. Here, the effect of COI1 overexpression on the growth of stably transformed arabidopsis cell cultures is described. Methods: Time-course experiments were carried out to analyse gene expression, and protein and metabolite levels. Key Results: Both MeJA treatment and the overexpression of COI1 modify growth, by altering cell proliferation and expansion. DNA content as well as transcript patterns of cell cycle and cell wall remodelling markers were altered. COI1 overexpression also increases the protein levels of OLIGOGALACTURONIDE OXIDASE 1, BETA-GLUCOSIDASE/ENDOGLUCANASES and POLYGALACTURONASE INHIBITING PROTEIN2, reinforcing the role of COI1 in mediating defence responses and highlighting a link between cell wall loosening and growth regulation. Moreover, changes in the levels of the primary metabolites alanine, serine and succinic acid of MeJA-treated Arabidopsis cell cultures were observed. In addition, COI1 overexpression positively affects the availability of metabolites such as β-alanine, threonic acid, putrescine, glucose and myo-inositol, thereby providing a connection between JA-inhibited growth and stress responses. Conclusions: This study contributes to the understanding of the regulation of growth and the production of metabolic resources by JAs and COI1. This will have important implications in dissecting the complex relationships between hormonal and cell wall signalling in plants. The work also provides tools to uncover novel mechanisms co-ordinating cell division and post-mitotic cell expansion in the absence of organ developmental control

A Regulatory Network for Coordinated Flower Maturation

For self-pollinating plants to reproduce, male and female organ development must be coordinated as flowers mature. The Arabidopsis transcription factors AUXIN RESPONSE FACTOR 6 (ARF6) and ARF8 regulate this complex process by promoting petal expansion, stamen filament elongation, anther dehiscence, and gynoecium maturation, thereby ensuring that pollen released from the anthers is deposited on the stigma of a receptive gynoecium. ARF6 and ARF8 induce jasmonate production, which in turn triggers expression of MYB21 and MYB24, encoding R2R3 MYB transcription factors that promote petal and stamen growth. To understand the dynamics of this flower maturation regulatory network, we have characterized morphological, chemical, and global gene expression phenotypes of arf, myb, and jasmonate pathway mutant flowers. We found that MYB21 and MYB24 promoted not only petal and stamen development but also gynoecium growth. As well as regulating reproductive competence, both the ARF and MYB factors promoted nectary development or function and volatile sesquiterpene production, which may attract insect pollinators and/or repel pathogens. Mutants lacking jasmonate synthesis or response had decreased MYB21 expression and stamen and petal growth at the stage when flowers normally open, but had increased MYB21 expression in petals of older flowers, resulting in renewed and persistent petal expansion at later stages. Both auxin response and jasmonate synthesis promoted positive feedbacks that may ensure rapid petal and stamen growth as flowers open. MYB21 also fed back negatively on expression of jasmonate biosynthesis pathway genes to decrease flower jasmonate level, which correlated with termination of growth after flowers have opened. These dynamic feedbacks may promote timely, coordinated, and transient growth of flower organs

Livestock disease surveillance and biosecurity priorities in the Pacific Island countries and territories

Livestock play an important role in the social, cultural and economic environment of the Pacific Island countries and territories (PICTs). Currently, the development of the livestock sector in the Pacific region is constrained by a number of factors, including animal health status requirements. So far, the Pacific Islands region has a favourable animal health situation but it is a challenge to maintain a disease free environment in an area composed of 25,000 islands dispersed over 180 million square kilometres. While most of the PICTs face a critical shortage of veterinarians and have limited financial resources, this study aims to examine ways by which animal disease surveillance in the Pacific Islands region could be better targeted to enable more efficient use of scarce resources in the PICTs. Within this context, a literature review was conducted to synthesize data across studies from peer-reviewed and grey literature on the animal diseases in the Pacific Islands region. Based on the outputs of the meta-analysis, a multicriteria prioritization process was then developed to identify animal diseases perceived to be of importance by decision makers within selected PICTs, at the regional and national levels. Pig and poultry husbandry being of primary importance for the Pacific communities, farmer practices and the movements of pigs and poultry were then examined in four selected PICTs (Fiji, Papua New Guinea, Solomon Islands and Vanuatu), using questionnaire survey and social network analysis tools in view of better predicting how diseases could potentially spread in the region. Finally, a combined pig and poultry market chain and risk pathway analysis was conducted in these four PICTs to identify the highest risk areas (risk hotspots) and risky practices and behaviours (risk factors) of animal disease introduction and/or spread, using highly pathogenic avian influenza (HPAI) and foot-and-mouth disease (FMD) as model diseases because of their potential importance in the region. From the 158 eligible references retrieved from the literature review, only 77 (48.7%) were published since 1992 and analysed in more details. A total of 101 diseases and pathogens were reported on for domestic animals in the Oceania region and in 17 PICTs in particular. Retrieved literature on animal diseases in PICTs was scarce and no longer up to date. There is a need to improve the published knowledge on the current animal disease status in the region. The list of the top-twenty ranked diseases for the Pacific Islands region resulting from the structured prioritization process shows a mix of endemic zoonotic diseases (such as leptospirosis ranked first; brucellosis third; tuberculosis sixth and endoparasites and ectoparasites respectively eleventh and thirteenth) with exotic diseases (such as highly pathogenic avian influenza (HPAI) ranked second, foot-and-mouth disease (FMD) fifth and rabies ninth). There were different disease ranking lists for each of the four targeted PICTs, confirming different strategies of disease prevention and control may be required for each country, rather than a regional approach. Interviewed animal health and production workers were unfamiliar with most of the prioritized diseases and a majority acknowledged that they would not be able to recognise clinical signs if outbreaks were to occur in their area. Results from the survey and the social network analysis indicate that a large proportion of farmers (44.6 to 61.3%) do not implement any preventive or control measures, yet, the majority (80.6 to 88%) did not experience any animal diseases over the past twelve-months. Most farmers never ask for veterinary care, never engage in laboratory testing and do not report when their animals show clinical signs. Many pig farmers (31.8%) trade within their communities only and sell directly to consumers (24.5%) which reduces the risk of diseases spreading. Our results show an association between farmers that report having had disease on their farm in the past twelve-months and movements of animals on and off their farms. The capitals of the studied provinces in PNG, Vanuatu and Solomon Islands were identified as the most connected nodes of both pig and poultry trade while Fiji networks appeared much less connected. Farmer practices increased the risk of disease spread but this was currently limited by trading practices. The conduct of the combined market chain analysis with risk pathways was a practical way of communicating risk to animal health officials and improving biosecurity. It provided a participatory approach that helps officials to better understand the trading regulations in place in their country and to better evaluate their role as part of the control system. Common risk patterns were found to play a role in all four PICTs. Legal trade pathways rely essentially on preventive measures put in place in the exporting countries while no or only limited control measures are undertaken by the importing countries. Legal importations of animals and animal products are done mainly by commercial farms which then supply local smallholders. Targeting surveillance on these potential hotspots would limit the risk of introduction and spread of animal diseases within the pig and poultry industry. Swill feeding is identified as a common practice in the region that represents a non-negligible risk factor for dissemination of pathogens to susceptible species. Illegal introduction of animals and animal products is suspected, but appears restricted to small holder farms in remote areas, limiting the risk of spread of transboundary animal diseases along the market chain. Introduction of undeclared goods hidden within a legal trade activity was identified as a major risk pathway. Activities such as awareness campaigns for pig and poultry farmers regarding disease reporting, biosecurity measures or danger of swill feeding and training of biosecurity officers in basic animal health and import-associated risks are recommended to prevent and limit the spread of pathogens within the PICTs. We put forward the methodology used for this study as a novel approach for more rational and transparent allocations of resources for enhancing food security and for better targeted approach to animal disease prevention and control. The results of this study are expected to lead to a more rational use of skilled manpower and increase the sensitivity of disease identification within the PICTs

RSK2 and Greatwall, two AGC kinases involved in the regulation of mitosis

La mitose est une phase importante du cycle cellulaire. Les mécanismes de surveillance s'assurent de l'ordre et de l'exécution correcte des événements du cycle cellulaire dont les erreurs peuvent conduire à l'aneuploïdie. Pendant la mitose, la séparation des chromatides sœurs est régulée par le point de contrôle du fuseau mitotique qui s'assure que tous les chromosomes sont correctement alignés sur la plaque métaphasique. L'entrée et la sortie de mitose sont régulées par l'activation et l'inactivation du complexe cycline B/Cdk1. Cette fine régulation fait intervenir de nombreuses kinases et phosphatases. Dans ce projet nous nous sommes intéressés plus particulièrement à deux AGC kinases : RSK2 et Greatwall (Gwl).Au cours de cette étude nous nous sommes proposés d'analyser l'implication de RSK2, substrat majeur de la MAPK, dans le point de contrôle du fuseau mitotique. Nos résultats montrent que RSK2 est essentielle pour l'activité du point de contrôle du fuseau mitotique dans les extraits d'œufs de xénope ainsi que pour la localisation des autres protéines de ce mécanisme de surveillance localisées aux kinétochores. Nous montrons également que RSK2 participe au point de contrôle dans les cellules humaines. En effet, RSK2 est nécessaire à la localisation aux kinétochores de Mad1, Mad2 et Cenp-E, protéines essentielles à l'activité de ce checkpoint. L'entrée et la sortie de mitose sont régulées par le complexe cycline B/Cdk1 et des phosphatases. Gwl est une nouvelle kinase essentielle à l'entrée en mitose et au maintien de l'état mitotique dans les extraits d'œufs de xénope. En effet, nos résultats montrent que Gwl maintient l'état mitotique indépendamment du complexe cycline B/Cdk1, en régulant négativement PP2A, une phosphatase responsable de la déphoshorylation des substrats mitotiques.Mitosis is an important phase of cell cycle. The Spindle Assembly Checkpoint (SAC) verifies the orders and the events correct execution of the cell cycle, as errors may lead to aneuploidy. During the mitosis, the checkpoint delays the anaphase onset until all chromosomes are correctly attached to the spindle‘s microtubules. Entry and Exit of mitosis are regulated by the activation and inactivation of cyclin B/Cdk1. A lot of kinases and phosphatases are involved in this fine regulation. In this project, we are particularly focusing on two AGC kinases: RSK2 and Greatwall (Gwl).In this study, we analyzed RSK2, a major substrates of MAPK, involvement in SAC. Our results show that RSK2 is essential to the activation of SAC in xenopus egg extracts and for the localization at the kinétochores of the others SAC components. We also show that RSK2 participate in the maintenance of the SAC in human cells. Indeed, RSK2 is necessary for Mad1, Mad2 and Cenp-E localization, essential proteins for SAC activation.Entry and exit of mitosis are regulated by cyclin B/Cdk1 complex and phosphatases. Gwl is a new kinase essential to the entry into mitosis and maintenance of the mitotic state in xenopus egg extracts. Indeed, our results showed that Gwl maintains the mitotic state independently of cyclin B/Cdk1 but with the negative regulation of PP2A, which dephosphorylate the mitotic substrate