Bacillus velezensis strain B26 modulates the inflorescence and root architecture of Brachypodium distachyon via hormone homeostasis

Root system architecture plasticity with beneficial rhizosphere microbes: Current findings and future perspectives

The rhizosphere microbiota, often referred to as the plant's "second genome" plays a critical role in modulating root system architecture (RSA). Despite this, existing methods to analyze root phenotypes in the context of root-microbe interactions remain limited, and the precise mechanisms affecting RSA by microbes are still not fully understood. This review comprehensively evaluates current root phenotyping techniques relevant to plant-microbe interactions, discusses their limitations, and explores future directions for integrating advanced technologies to elucidate microbial roles in altering RSA. Here, we summarized that microbial metabolite, primarily through auxin signaling pathways, drive root development changes. By harnessing advanced phenotyping tools, we aim to uncover more detailed mechanisms by which microbes modify RSA, providing valuable insights into strategies for optimizing nutrient uptake, bolstering food security, and enhancing resilience against climate-induced environmental stresses.

Bacterial endosymbionts of a nitrogen-fixing yeast Rhodotorula mucilaginosa JGTA-S1 - insights into a yet unknown micro-ecosystem

Rhodotorula mucilaginosa JGTA-S1 is a yeast strain capable of fixing nitrogen and improving nitrogen nutrition in rice plants because of its nitrogen-fixing endobacteria, namely Stutzerimonas (Pseudomonas) stutzeri and Bradyrhizobium sp. To gain a deeper understanding of yeast endosymbionts, we conducted a whole-genome shotgun metagenomic analysis of JGTA-S1 cells grown under conditions of nitrogen sufficiency and deficiency. Our results showed that the endosymbiont population varied depending on the nitrogen regime. Upon mechanical disruption of yeast cells, we obtained endosymbionts in culturable form viz. Bacillus velezensis and Staphylococcus sp. under nitrogen-replete conditions and Lysinibacillus telephonicus., Brevibacillus sp., and Niallia circulans under nitrogen-depleted conditions. S. stutzeri and Bradyrhizobium sp. the previously reported endosymbionts remained unculturable. The culturable endosymbionts Staphylococcus sp. and Bacillus velezensis appear to possess genes for dissimilatory nitrate reduction (DNRA), an alternative pathway for ammonia synthesis. However, our findings suggest that these endosymbionts are facultative as they survive outside the host. The fitness of the yeast was not affected by curing of these microbes. Curing the yeast diazotrophic endosymbionts took a toll on its fitness. Our results also showed that the populations of S. stutzeri and B. velezensis increased significantly under nitrogen-depleted conditions compared to nitrogen-sufficient conditions. The importance of DNRA and nitrogen fixation is also reflected in the metagenomic reads of JGTA-S1.

How do arbuscular mycorrhizas affect reproductive functional fitness of host plants?

Arbuscular mycorrhizal (AM) symbiosis in soil may be directly or indirectly involved in the reproductive process of sexually reproducing plants (seed plants), and affect their reproductive fitness. However, it is not clear how underground AM symbiosis affects plant reproductive function. Here, we reviewed the studies on the effects of AM symbiosis on plant reproductive fitness including both male function (pollen) and female function (seed). AM symbiosis regulates the development and function of plant sexual organs by affecting the nutrient using strategy and participating in the formation of hormone networks and secondary compounds in host plants. The nutrient supply (especially phosphorus supply) of AM symbiosis may be the main factor affecting plant's reproductive function. Moreover, the changes in hormone levels and secondary metabolite content induced by AM symbiosis can also affect host plants reproductive fitness. These effects can occur in pollen formation and transport, pollen tube growth and seed production, and seedling performance. Finally, we discuss other possible effects of AM symbiosis on the male and female functional fitness, and suggest several additional factors that may be involved in the influence of AM symbiosis on the reproductive fitness of host plants. We believe that it is necessary to accurately identify and verify the mechanisms driving the changes of reproductive fitness of host plant in symbiotic networks in the future. A more thorough understanding of the mechanism of AM symbiosis on reproductive function will help to improve our understanding of AM fungus ecological roles and may provide references for improving the productivity of natural and agricultural ecosystems.