Immediate impacts of COVID-19 crisis on agricultural and food systems in the Caribbean.

Context: In a region already plagued by food insecurity and challenges to the sustainability of the agricultural sector, the COVID-19 pandemic was a brutal shock in the Caribbean with immediate and significant socio-economic consequences. Objective: In this paper, we assessed what are the immediate impacts of the COVID-19 crisis on the agricultural and food systems of the Caribbean. Methods: To this end, we conducted online surveys among farmers, households and experts of the region. We assessed the nature, strength and reversibility of the impacts but also the factors of resilience in the face of the crisis. Results and conclusions: Our study shows that the COVID-19 crisis has had strong impacts on Caribbean farmers and has weakened agricultural systems. The main impacts identified were a drop in income, production losses due to difficulties in marketing through conventional channels, but also difficulties in managing the farming systems due to reduced access to inputs and labor. In order to cope, farmers have adapted to be more self-sufficient: reduction in the size of cultivated areas, search for short marketing channels, diversification of production and reorientation towards the needs of the local market, recourse to mutual aid between farmers. If these effects appear to be non-irreversible in an island like Guadeloupe, the situation is different in other islands of the region where farmers have had to sell livestock, seek new off-farm income and sometimes sell land to cope. In terms of impacts on food systems, the crisis has led to strong constraints such as a reduction in food intake and diversity and increased reliance on family and social mutual aid. Our study also shows that the crisis has had an impact on consumer behavior and their perception of the importance of the agricultural sector: reduction of food waste, return to fresh and local products, adaptation of the diet, consumption of new products, and cultivation of food gardens. Finally, our study shows that the crisis has had an effect of strengthening the links between farmers and the rest of the population. Significance: Thus if the crisis has had seriously damaging consequences, it can also be the trigger and catalyst for an agro-ecological transition and the development of a circular and territorialized bio-economy to strengthen the resilience of Caribbean agricultural and food systems and facilitate the achievement of sustainability and food security objectives.

Kremen1 and Dickkopf1 control cell survival in a Wnt-independent manner.

In multicellular organisms, a tight control of cell death is required to ensure normal development and tissue homeostasis. Improper function of apoptotic or survival pathways can not only affect developmental programs but also favor cancer progression. Here we describe a novel apoptotic signaling pathway involving the transmembrane receptor Kremen1 and its ligand, the Wnt-antagonist Dickkopf1. Using a whole embryo culture system, we first show that Dickkopf1 treatment promotes cell survival in a mouse model exhibiting increased apoptosis in the developing neural plate. Remarkably, this effect was not recapitulated by chemical Wnt inhibition. We then show that Dickkopf1 receptor Kremen1 is a bona fide dependence receptor, triggering cell death unless bound to its ligand. We performed Wnt-activity assays to demonstrate that the pro-apoptotic and anti-Wnt functions mediated by Kremen1 are strictly independent. Furthermore, we combined phylogenetic and mutagenesis approaches to identify a specific motif in the cytoplasmic tail of Kremen1, which is (i) specifically conserved in the lineage of placental mammals and (ii) strictly required for apoptosis induction. Finally, we show that somatic mutations of kremen1 found in human cancers can affect its pro-apoptotic activity, supporting a tumor suppressor function. Our findings thus reveal a new Wnt-independent function for Kremen1 and Dickkopf1 in the regulation of cell survival with potential implications in cancer therapies.

Netrin-1 acts as a survival factor via its receptors UNC5H and DCC.

The membrane receptors DCC and UNC5H have been shown to be crucial for axon guidance and neuronal migration by acting as receptors for netrin-1. DCC has also been proposed as a dependence receptor inducing apoptosis in cells that are beyond netrin-1 availability. Here we show that the netrin-1 receptors UNC5H (UNC5H1, UNC5H2, UNC5H3) also act as dependence receptors. UNC5H receptors induce apoptosis, but this effect is blocked in the presence of netrin-1. Moreover, we demonstrate that UNC5H receptors are cleaved in vitro by caspase in their intracellular domains. This cleavage may lead to the exposure of a fragment encompassing a death domain required for cell death induction in vivo. Finally, we present evidence that during development of the nervous system, the presence of netrin-1 is crucial to maintain survival of UNC5H- and DCC-expressing neurons, especially in the ventricular zone of the brainstem. Altogether, these results argue for a role of netrin-1 during the development of the nervous system, not only as a guidance cue but as a survival factor via its receptors DCC and UNC5H.