Biology subjects

Holm, K.

Publications and source records attributed to Holm, K..

3 recordsLinked to original sources

bioRxiv2025

Ultra long-lived plasma cells in the human small intestine produce microbiota-reactive IgA antibodies

A large fraction of the intestinal microbiota is highly coated with secretory IgA, and bacteria-specific IgA is believed to shape the composition of the microbiota. A hallmark of the adaptive immune system is immunological memory to specific antigens. However, whether there is strong and persistent memory of secretory antibodies to bacterial antigens has not been determined. Here we show that ultra long-lived CD19- CD45- (age>20 years) plasma cells (PCs) residing in the human small intestine produce IgA that binds to most taxa of a diverse anaerobic microbiota culture. Long-lived CD19-CD45+ (age>10 years) and short-lived CD19+CD45+ (age<2 years) PCs also produced IgA with broad bacterial reactivity. A clear correlation between high-binding and low-binding taxa was observed across the PC subsets. We also found that host PCs were depleted in acute intestinal graft versus host disease, a condition strongly associated with loss of microbiota diversity. Together, we show that bacterial antigens in the intestine induce an extremely stable, long-lasting humoral immune memory that may be important for the long-term stability and resilience of the intestinal microbiome.

immunology↗

bioRxiv2020

Phenotypic plasticity, population structure and adaptation in a young weed species with a worldwide distribution

The colonization success of a species depends on phenotypic plasticity, adaptive potential and population structure. Assessing their relative contributions during a colonization process is challenging, and a large-scale experiment had yet to be done. In this study, we attempted to tease apart their effects on the fitness of one of the most common plant on Earth, the shepherds purse (Capsella bursa-pastoris), a self-fertilizing and allopolyploid weed, with a worldwide distribution. The overarching goal is to eventually understand how the shepherds purse extensive distribution range was established so rapidly. To do so, we carried out three common gardens, located in Europe, Asia and North America, and measured several life-history traits on field-collected accessions belonging to three distinct genetic clusters (Middle East, Europe, and Asia). Our experiment showed that (i) the success of C. bursa-pastoris is mainly due to its high degree of phenotypic plasticity; and (ii), genetic cluster effect reflected a classic pattern observed in core vs marginal populations, with the Middle Eastern cluster (putative core population) outperforming the European and Asian clusters. This study therefore revealed, in a model species, different relative contributions of plasticity and adaptation to fitness, depending on the population and the time since colonization occurred.

evolutionary biology↗

bioRxiv2018

Local adaptation and maladaptation during the worldwide range expansion of a self-fertilizing plant

Species having experienced rapid range expansion represent unique opportunities to evaluate the dynamics of adaptation during colonization of new environments. We investigated the consequences of range expansion on local adaptation of a successful worldwide colonizer, the shepherds purse Capsella bursa-pastoris. This species is an annual weed that originated recently in Eurasia and has now broadly colonized both temperate and subtropical areas. We assessed the performance, genetic diversity, and phenology of field-collected accessions belonging to three distinct genetic clusters of decreasing age (Middle East, Europe and Asia) in three common gardens in Europe, Asia and North America. To understand the genetic basis of local adaptation in this species, we also tested for correlation between SNP allele frequencies and environmental factors in Europe and Asia. Overall, we showed that patterns of local adaptation depended on population history: some older populations were weakly adapted to local conditions while those closer to the front of the colonization wave, far from the origin of the species, were maladapted whatever the common gardens. Altogether, our results have important consequences for the understanding of the evolution and adaptation of self-fertilizing plant during range expansion.

evolutionary biology↗