Quantitative Proteomics at Early Stages of the Symbiotic Interaction Between Oryza sativa and Nostoc punctiforme Reveals Novel Proteins Involved in the Symbiotic Crosstalk

Abstract

Symbiosis between cyanobacteria and plants is considered pivotal for biological nitrogen deposition in terrestrial ecosystems. Despite extensive knowledge of the ecology of plant-cyanobacterium symbioses, little is known about the molecular mechanisms involved in recognition between partners. Here, we conducted a quantitative sequential window acquisition of all theoretical fragment ion spectra mass spectrometry (SWATH-MS) pipeline to analyse protein changes in Oryza sativa and Nostoc punctiforme during early events of symbiosis. We found differentially expressed proteins in both organisms linked to several biological functions, including signal transduction, adhesion, defence-related proteins, and cell wall modification. In Nostoc punctiforme we found increased expression in 62 proteins that have been previously described in other Nostoc-plant symbioses, reinforcing the robustness of our study. Our findings reveal new proteins activated in the early stages of the Nostoc-Oryza symbiosis that might be important for the recognition between the plant and the host. Oryza mutants in genes in the common symbiosis signalling pathway (CSSP) show a reduced colonization efficiency providing first insights on the involvement of the CSSP for the accommodation of N. punctiforme inside the plant cells. This information may have long-term implications for a greater understanding of the symbiotic interaction between Nostoc and land plants.

Phylometagenomics of cycad coralloid roots reveals shared symbiotic signals

“…Two of these COG groups, T in SYMB-1 and SYMB-2 and Q in SYMB-1 and SYMB-2, stand out, as they were the only two COGs with both enriched and unique genes. COG group T corresponds to signal transduction mechanisms that may contribute to the cyanobiont's ability to recognize the host chemical signals, which is a necessary step in the establishment of symbiosis [25,77,78]. The high number of genes found in COG group Q, which corresponded to secondary metabolism, indicated that natural products might play a more significant role in the symbiosis than previously thought, consistent with observations made on the uniqueness of metabolites in cyanobionts [5,14].…”

“…Taken together, the combined results from this and the previous subsection strongly suggest that at least two phylogenetically and functionally different lineages of facultative Nostocales cyanobionts exist. One of these lineages, containing all genomes in SYMB-2 and 3, is enriched in unique genes with functional annotations that are congruent with functions that have been found to be necessary for symbiosis, such as motility, signal transduction mechanisms and carbohydrate metabolism [25, 28, 77, 78], as well as those necessary for biosynthesis of unique natural products, which are characteristic of cyanobionts [5, 14]; and could play an active role in the symbiosis [79, 80]. The remaining lineage, which includes all genomes from SYMB-1, has a unique enrichment/decrement pattern that does not seem to be driven by differential genes.…”

Challenging the term symbiosis in plant–microbe associations to create an understanding across sciences

“…In the field of molecular plant sciences, some researchers argue that evidence of a mutual exchange of chemicals or symbiogenesis of specific organs is required. However, there are examples of well defined plant–microbe symbiotic interactions that do not require the development of specific organs in the plant (Khan et al, 2012; Alvarenga and Rousk, 2022; Álvarez et al, 2022). In the same way, there is evidence of symbiotic interactions in which clear benefits to both partners cannot be ascertained and, thus, their categorization as mutualistic is debated.…”

“…In the same way, there is evidence of symbiotic interactions in which clear benefits to both partners cannot be ascertained and, thus, their categorization as mutualistic is debated. One example is the Oryza – Nostoc association, in which the chemical exchange is not yet directly proven, despite documentation of endophytic colonization and an increase in plant yield in co‐cultivation (Álvarez et al, 2022). Hence, often neither symbiosis nor mutualism are applied to describe rice–cyanobacteria associations, resulting in a potential disregard of these interactions.…”

“… Three cases of debated or overlooked associations of land plants with cyanobacteria (A) While the role of cyanobacterial nitrogen fixation and its role in improving the fertility of rice ( Oryza ) fields has been studied for almost a century, the endophytic association of Nostoc punctiforme and rice has only recently been recreated in vitro (Álvarez et al, 2022). The exchange of photosynthetic polysaccharides and fixed nitrogen between rice and cyanobacteria is depicted schematically.…”