Biology subjects

Bisseling, T.

Publications and source records attributed to Bisseling, T..

7 recordsLinked to original sources

bioRxiv2026

Long-Term Grazing Drives Compositional Shifts in Root-Associated Microbial Communities of Desert Steppe Plants

Grassland microbial communities are central to mediating ecosystem function and stability, yet how long-term grazing reshapes root-associated microbiomes across contiguous soil-root habitats remains poorly understood. This limits our ability to identify robust microbial bioindicators for grassland health monitoring. In this study, we investigated the community assembly and functional variation of root-associated microbiomes of Stipa breviflora, a dominant perennial clonal grass in desert steppes, across a 17-year continuous grazing experiment with four grazing intensity treatments (no grazing, light, moderate, and heavy grazing). We show that grazing intensity induces niche-specific restructuring of microbial communities, with the most profound compositional and functional shifts occurring in the rhizosphere, followed by root endophytic compartments and bulk soil. Light and moderate grazing significantly enriches the phylum Bacillota in rhizosphere and endophytic compartments, whereas the genus Pseudomonas dominates ungrazed grassland soils and is markedly depleted under grazing conditions. Microbial community responses to grazing follow a unimodal intermediate disturbance pattern, with moderate grazing triggering the strongest microbial community differentiation, enhanced microbial network connectivity and modularity, and the highest abundance of grazing-responsive microbial biomarkers. Notably, grazing-induced microbial community variation is decoupled from intraspecific phenotypic changes in S. breviflora. Our findings demonstrate that long-term grazing acts as a strong selective filter partitioning core beneficial microbial taxon, establishing Bacillota and Pseudomonas as complementary bioindicators for evaluating desert steppe ecosystem health. This study advances the understanding of plant-microbe interactions under anthropogenic disturbance and provides microbiome-based insights for sustainable grassland management.

microbiology↗

bioRxiv2026

Nod factor signaling controlled genes in Medicago truncatula nodules

O_LILegume nodule formation is induced by rhizobia secreted Nod factors (NFs). It has been shown that NF receptors also accumulate in the apex of Medicago truncatula nodules. However, the NF signaling induced transcriptional changes in there have never been studied. C_LIO_LIHere, we studied this by using NF signaling mutant TE7, a weak allele of IPD3, blocked in rhizobial release. Nodule apices were isolated with laser microdissection and used for transcriptional analysis. C_LIO_LIWe identified 1655 NF signaling controlled genes in nodule apex. By comparing this with the transcriptome data from VAMP721d&e RNAi nodule apices, we identified a subset of 445 genes whose expression depends on NF signaling and rhizobial release. Further, we compared the set of genes controlled by NF signaling in nodule apices with that controlled in root epidermis, and these showed only a small overlap. NIN is induced by NF signaling both in the root epidermis and in the nodule. By overexpression of NIN in TE7 and knock down of NIN in wildtype nodules we showed that NF signaling controlled rhizobial release depends on NIN. C_LIO_LINF signaling controls a distinct set of genes in nodules, the function of which depends at least in part on NIN. C_LI

Developmental Biology↗

bioRxiv2025

Evolutionary predisposition of NIN to function in nitrogen-fixing nodules

Nitrogen-fixing nodule symbiosis is an ecologically and economically important trait in legumes and some related species. A critical step in the evolution of nodulation is the recruitment of NODULE INCEPTION (NIN); a homolog of the nitrate-sensing NIN-LIKE PROTEIN (NLP) transcription factors. However, whether adaptations have occurred in the NIN protein upon its recruitment in symbiosis remains elusive. Here we show that non-symbiotic NIN orthologs can function in intracellular infection and even nodule initiation, demonstrating that these properties of NIN predate the evolution of nodulation. Concurrent with the evolution of nodulation, symbiotic NIN proteins were optimized for their role in symbiosis by acquiring nitrate independent functionality, including constitutive nuclear localization. A single amino acid substitution in Arabidopsis AtNLP2 enhances its nuclear localization under low nitrate conditions, making it functionally comparable to a symbiotic NIN. These findings highlight that NIN was predisposed to function in nodulation at the time of its recruitment into nitrogen-fixing symbiosis. Our study provides novel insight in how and why non-symbiotic NIN orthologues could be recruited to function in nitrogen-fixing root nodule symbiosis.

plant biology↗

bioRxiv2023

Nodule organogenesis in Medicago truncatula requires local stage-specific auxin biosynthesis and transport

The importance of auxin in plant organ development including root nodule formation is well established. Using auxin reporter constructs the spatiotemporal auxin distribution pattern during nodule development has previously been illustrated. However, our understanding of how this pattern is built-up and maintained still remains elusive. To this end, we studied how the auxin gradient visualized by DR5 expression patterns at different stages of nodule development in Medicago truncatula (Medicago), is correlated with the spatiotemporal expression patterns of known auxin biosynthesis and auxin transport genes. In addition, we record the MtPIN10-GFP expression pattern and polar positioning on the cell plasma membranes during nodule primordium development to investigate the auxin flux. RNA interference and the application of auxin synthesis blockers were used to demonstrate the relevance of biosynthesis and transport at the initial stages of the nodulation process. Our results show that upon rhizobium inoculation, preceding the first mitotic activity, a specific set of MtYUCs and MtPINs as well as MtLAX2 are expressed in the pericycle contributing to the creation of an auxin maximum. Overall, we demonstrate that dynamic spatiotemporal expression of both, MtYUCs and MtPINs, result in specific auxin outputs in subsequent stages of nodule primordia and nodule meristem formation.

plant biology↗

bioRxiv2021

Medicago SPX1 and SPX3 regulate phosphate homeostasis, mycorrhizal colonization and arbuscule degradation

To acquire sufficient mineral nutrients such as phosphate (Pi) from the soil, most plants engage in a symbiosis with arbuscular mycorrhizal (AM) fungi. Attracted by plant-secreted strigolactones, the fungi colonize the roots and form highly-branched hyphal structures called arbuscules inside inner cortex cells. It is essential that the host plant controls the different steps of this interaction to maintain its symbiotic nature. However, how plants sense the amount of Pi obtained from the fungus and how this determines the arbuscule lifetime is far from understood. Here, we show that Medicago truncatula SPX-domain containing proteins SPX1 and SPX3 regulate root phosphate starvation responses as well as fungal colonization and arbuscule degradation. SPX1 and SPX3 are induced upon phosphate starvation but become restricted to arbuscule-containing cells upon establishment of the symbiosis. Under Pi-limiting conditions they facilitate the expression of the strigolactone biosynthesis gene DWARF27, which correlates with increased fungal branching by root exudates and increased root colonization. Later, in the arbuscule-containing cells SPX1 and SPX3 redundantly control the timely degradation of arbuscules. This regulation does not seem to involve direct interactions with known transcriptional regulators of arbuscule degradation. We propose a model where SPX1 and SPX3 control arbuscule degeneration in a Pi-dependent manner via a yet-to-identify negative regulator.

plant biology↗

bioRxiv2020

Plant-specific histone deacetylases are essential for early as well as late stages of Medicago nodule development

Legume and rhizobium can establish a nitrogen-fixing nodule symbiosis. Previous studies have shown that several transcription factors that play a role in (lateral) root development are also involved in nodule development. Chromatin remodelling factors, like transcription factors, are key players in regulating gene expression. However, it has not been studied whether chromatin remodelling genes that are essential for root development get involved in nodule development. Here we studied the role of Medicago histone deacetylases (MtHDTs) in nodule development. Their Arabidopsis orthologs have been shown to play a role in root development. The expression of MtHDTs is induced in nodule primordia and is maintained in nodule meristem and infection zone. Conditional knock-down of their expression in a nodule-specific way by RNAi blocks nodule primordium development. A few nodules still can be formed but their nodule meristems are smaller and rhizobial colonization of the cells derived from the meristem is markedly reduced. Although the HDTs are expressed during nodule and root development, transcriptome analyses indicate that HDTs control the development of these organs in a different manner. During nodule development the MtHDTs positively regulate 3-hydroxy-3-methylglutaryl coenzyme a reductase 1 (MtHMGR1). The decreased expression of MtHMGR1 is sufficient to explain the block of primordium formation. ONE SENTENCE SUMMARYPlant-specific histone deacetylases regulate the expression of 3-hydroxy-3-methylglutaryl-coenzyme A reductases to control root nodule development.

developmental biology↗

bioRxiv2017

Parallel loss of symbiosis genes in relatives of nitrogen-fixing non-legume Parasponia

Rhizobium nitrogen-fixing nodules are a well-known trait of legumes, but nodules also occur in other plant lineages either with rhizobium or the actinomycete Frankia as microsymbiont. The widely accepted hypothesis is that nodulation evolved independently multiple times, with only a few losses. However, insight in the evolutionary trajectory of nodulation is lacking. We conducted comparative studies using Parasponia (Cannabaceae), the only non-legume able to establish nitrogen fixing nodules with rhizobium. This revealed that Parasponia and legumes utilize a large set of orthologous symbiosis genes. Comparing genomes of Parasponia and its non-nodulating relative Trema did not reveal specific gene duplications that could explain a recent gain of nodulation in Parasponia. Rather, Trema and other non-nodulating species in the Order Rosales show evidence of pseudogenization or loss of key symbiosis genes. This demonstrates that these species have lost the potential to nodulate. This finding challenges a long-standing hypothesis on evolution of nitrogen-fixing symbioses, and has profound implications for translational approaches aimed at engineering nitrogen-fixing nodules in crop plants.

plant biology↗